Determination of glycyrrhetic acid in human plasma by HPLC-MS method and investigation of its pharmacokinetics

Objective: To develop a high performance liquid chromatography mass spectrometry (HPLC‐MS) method for the determination of the glycyrrhetic acid (GA) in human plasma and for the investigation of its pharmacokinetics after the oral administration of 150 mg diammonium glycyrrhizinate test and reference capsule formulations. Methods: The GA in plasma was extracted with ethyl acetate, separated on a C₁₈ column with a mobile phase of methanol (5 mmol/L ammonium acetate)–water (85 : 15, V/V) and analysed using a MS detector. Ursolic acid (UA) was used as internal standard. The target ions were m/z 469·5 for GA and m/z 455·6 for UA, the fragment voltages were 200 V and 100 V for GA and UA respectively. Results: The calibration curve was linear over the range of 0·5–200 ng/mL (r = 0·9974). The limit of quantification for GA in plasma was 0·5 ng/mL, the recovery was 76·0–80·0%, and the inter‐ and intra‐day relative standard deviations (RSD) were <12%. The pharmacokinetic parameters of GA after a single dose of 150 mg diammonium glycyrrhizinate test and reference were as follows: the half life (t_1/2) 9·65 ± 3·54 h and 9·46 ± 2·85 h, the time to peak concentration (T_max) 10·95 ± 1·32 h and 11·00 ± 1·30 h, the peak concentration (C_max) 95·57 ± 43·06 ng/mL and 103·89 ± 49·24 ng/mL; the area under time‐concentration curve (AUC_0–48 and AUC_0–∞) 1281·84 ± 527·11 ng·h/mL and 1367·74 ± 563·27 ng·h/mL, 1314·32 ± 566·40 ng·h/mL and 1396·97 ± 630·06 ng·h/mL. The relative bioavailability of diammonium glycyrrhizinate capsule was 98·88 ± 12·98%. Conclusion: The assay was sensitive, accurate and convenient, and can be used for the determination of GA in human plasma. Comparison of the bioavailability and pharmacokinetic profile of GA indicated that the test and reference capsules were bioequivalent.     

Estimation of the area under the curve for mycophenolic acid in adult renal transplant patients with concomitant tacrolimus using a limited sampling strategy

Objectives: The aim of this study was to develop a limited sampling strategy (LSS) for monitoring the use of mycophenolic acid (MPA) in maintenance therapy with tacrolimus (TCL) in renal transplant patients. Methods: Eighteen adult patients receiving a first transplant were investigated. All patients were treated with a combination of TCL, steroid and mycophenolate mofetil (MMF). Besides the predose trough concentration (C₀), whole blood samples were taken for measurement of the MPA concentration at 0·5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 h for a 14‐point 12‐h pharmacokinetic (PK) profile. Using stepwise linear regression analysis, an abbreviated area under the concentration time curve (AUC) was calculated using all 14, and any combination of sampling points to give an estimating equation with up to three predictors. Results: The equation derived from C₂, C₇ and C_12, for AUC estimation: AUC = (2·05 × C₂) + (8·51 ×C₇) + (2·29 × C₁₂) + 4·24. was found to be optimal. Using this formula, there was an excellent correlation between the estimated 3‐point AUC and AUC_{0–12 h}. To assess the agreement between the abbreviated methods and the full PK profile, we plotted the average AUC of the abbreviated estimates and the full PK profile. This Bland‐Altman analysis indicated good agreement to within ±2 SD and a prediction variability of 7·56 μg × h/mL. Conclusion: Our proposed three‐sampling‐point estimate of AUCs is clinically acceptable. However, the sampling times are inconvenient for outpatients, and is recommended only for monitoring MMF treatment of inpatients with suspected toxicity or at high risk of organ rejection.     

Pharmacokinetics and pharmacodynamics of intravenous dexmedetomidine in healthy Korean subjects

What is known and Objective: Dexmedetomidine is a selective alpha2‐adrenoreceptor agonist used for sedation in critically ill patients. The current study aimed to evaluate the pharmacokinetics (PKs), pharmacodynamics and tolerability of intravenous dexmedetomidine in healthy Korean subjects. Methods: A randomized, double‐blind, placebo‐controlled study with three parallel dosage groups was conducted. Twenty‐four subjects were randomly assigned to placebo or one of three dexmedetomidine dosing regimens, 3 μg/kg/h for 10 min followed by 0·17 μg/kg/h for 50 min (low dose), 6 μg/kg/h for 10 min followed by 0·34 μg/kg/h for 50 min (middle dose) and 3·7 μg/kg/h for 35 min followed by 0·7 μg/kg/h for 25 min (high dose). Serial blood samples for PK analysis were taken up to 12 h. PK parameters were determined using non‐compartmental methods (WinNonlin^®), and a population PK model was developed using nonmem ^®. The sedative effect of dexmedetomidine was assessed by Ramsay sedation score and visual analogue scales/sedation. Adverse events, clinical laboratory tests, electrocardiograms, physical examinations and vital signs were monitored for tolerability assessment. Results: Six subjects were assigned to each of the three active treatment group or placebo group. The AUC_last of the low‐, middle‐ and high‐dose group were 1096·8 ± 119·9 (mean ± SD) ng*h/L, 2643·0 ± 353·2 ng*h/L and 5600·6 ± 411·0 ng*h/L, respectively. PK of dexmedetomidine was best described using a two‐compartment model. The typical value of the population model can be calculated using the following equations: central volume of distribution (L) = 19·9 (age/27)^0·954, peripheral volume of distribution (L) = 59·4, clearance (L/h) = 33·7 (albumin level/4·3)^1·42 and inter‐compartment clearance (L/h) = 67·7. Sedative effects were significantly increased by dexmedetomidine compared to placebo. The blood pressure and heart rate were decreased, but oxygen saturation was maintained stable. What is new and Conclusion: Dexmedetomidine shows linear PK characteristics and dose‐dependent sedative effects. A two‐compartment population PK model was developed for healthy Korean subjects. The PK parameter estimates are similar in Koreans and Caucasians.     

Persistence of counter-regulatory abnormalities in insulin-dependent diabetes mellitus after pancreas transplantation

Abstract Conventional insulin therapy does not correct the counter-regulatory abnormalities of insulin-dependent diabetes mellitus. Pancreas transplantation is an alternative therapy that restores the endogenous insulin secretion in diabetes. In this study, the effects of segmental pancreas transplantation on counter-regulation to mild hypoglycaemia were evaluated. Glucose kinetics and the counter-regulatory hormonal responses were assessed in eight insulin-dependent diabetics with end-stage renal failure who had received pancreas and kidney transplantation 1 year previously, seven diabetic uraemic subjects (candidates for combined transplantation), five patients with chronic uveitis on immunosuppressive therapy comparable to pancreas recipients and 10 normal subjects. Insulin (0·3 mU kg^-1 min^-1) was infused for 2h to induce mild hypoglycaemia (plasma glucose 3·2–3·5-mmol l^-1) and exogenous glucose was infused as required to prevent any glucose decrease below 3·1 mmol l^-1. After transplantation, two of eight recipients had hypoglycaemic episodes reported in their medical records. During the study, hepatic glucose production was rapidly suppressed in the controls and in the patients on immunsuppression (–80 ± 7 and –54 ± 7%, P < 0·001 vs. basal), and rebounded to the baseline values within 1 h (–3 ± 1 and –6 ± 2%, P= NS vs. basal). The transplant recipients had similar suppression in the first hour (–88 ± 8%, P < 0·001 vs. basal), but the suppression persisted in the second hour (–69 ± 11%, P < 0·001 vs. basal) indicating a lack of glucose counter-regulatory response. The uraemic-diabetics had reduced suppression of hepatic glucose production (–45 ± 14%, P < 0·001 vs. basal) with respect to the recipients (P < 0·001), but had the same lack of response in the second hour (suppression: –39 ± 12%, P < 0·001 vs. basal). In addition, the response of glucagon to hypoglycaemia was blunted in both the recipients and in the diabetic subjects. In conclusion, the alterations in glucose counter-regulation of insulin-dependent diabetes persists after segmental pancreas transplantation. Specifically, the increased sensitivity of hepatic glucose production to the action of insulin renders this defect more evident after transplantation.     

A limited sampling strategy for estimating mycophenolic acid area under the curve in adult heart transplant patients treated with concomitant cyclosporine

Objective: Heart transplantation studies have shown a relationship between the mycophenolic acid area under the curve (AUC) 0–12 h (MPA AUC_0–12h) values and risk of acute rejection episodes and fewer side‐effects in patient receiving cyclosporine during the first year post‐transplant. However, measurement of full AUC is costly and time consuming and in this case it is an impractical approach to drug monitoring. Therefore, the authors describe a limited sampling strategy to estimate the MPA AUC_0–12h value in adult heart transplant recipients. Methods: Ninety MPA pharmacokinetic (PK) profiles were studied. The samples were collected immediately before and 0·5, 1, 1·5, 2, 2·5, 3, 4, 6, 9, 12 h after the morning dose of mycophenolate mofetil (MMF) following an overnight fast. PK profiles were determined at 6–8 weeks, 6, 12 months and more than 1 year after transplantation. Using stepwise multiple linear regression analysis a sampling strategy from 60 of PK profiles was obtained and next the bias and precision of the model were evaluated in another 30 PK profiles. Results: The three‐point model using C_0·5h, C_1h, C_2h was found to be superior to all other models tested (r² = 0·841). The regression equation for AUC estimation which gave the best fit to this model is: 9·69 + 0·63C_0·5 + 0·61C₁ + 2·20C₂. Using that model 63 of the 90 (70%) full AUC values were estimated within 15% of their actual value. For the best‐fit model, the mean prediction error was 3·2%, with 95% confidence intervals for prediction error to range from ?42·2% to 40·3%. All other models which use one, two or three time‐points over the first 2 h are poorer predictors of the full AUC than the model above. Conclusion: The proposed three time‐point equation to estimate AUC will be helpful in optimizing immunosuppressive therapy in heart transplantation.     

Clinical outcomes of lung-transplant recipients treated by voriconazole and caspofungin combination in aspergillosis

Background and objective: Invasive pulmonary aspergillosis (IPA) is a serious cause of death among immune‐compromised patients such as organ‐transplant recipients. Recently, voriconazole has been approved for first‐line therapy in IPA. Theoretically, optimal voriconazole blood level (superior to 1 mg/L according to recent studies) should be reached within 24 h. In practice, a significantly longer time seems to be needed in lung‐transplant recipients. Therefore, caspofungin is now used in combination with voriconazole to provide cover against Aspergillus spp. infection during this gap. The first aim of this study was to investigate Aspergillus spp. infection treated with this combination and the atter’s tolerability. The median time for attainment of apparently active blood levels in lung transplant recipients were compared between those with cystic fibrosis and those without. Methods: Lung‐transplant recipients who received a combination of voriconazole and caspofungin between 2002 and 2008 as primary therapy were identified retrospectively. The median number of days to reach active voriconazole blood levels was compared between cystic fibrosis and other patients by Student’s t‐test. Statistical significance was defined by P‐value <0·05. Results: Four patients were treated for Aspergillus colonization before transplantation and their culture were negative at 90 days. Eleven patients were treated for proven or probable invasive aspergillosis and 14 of them had a complete response. Hallucinations (n = 2) and significant hepatic toxicity (n = 2) were reported. Among the 15 studied transplant recipients, a median of 12·3 days was observed for active voriconazole blood levels to be reached. With cystic fibrosis patients, time tended to be longer than with other recipients (14·9 days vs. 8·3 days). Tacrolimus blood levels (between 5 and 15 ng/mL) may have been increased by voriconazole. Conclusion: This retrospective study describes practical experience in the management of this rare and severe disease in a referral centre for cystic fibrosis lung transplantation. Voriconazole and caspofungin combination was acceptably safe and was associated with good clinical outcomes in almost all patients. We showed that in 15 lung‐transplant recipients a median of 12·3 days was required for voriconazole to reach high enough blood levels. Caspofungin in combination with voriconazole provides cover against Aspergillus infection during the period when voriconazole may be at subtherapeutic levels with good tolerability.     

The efficacy and toxicity of two dosing-regimens of amikacin in neonates with sepsis

What is known and objective: Neonatal sepsis is one of the most common reasons for admission to neonatal units in developing countries. Aminoglycosides widely used in its treatment are usually administered two or three times a day. Less frequent doing may be more convenient and as effective. We aim to compare the efficacy and safety (nephrotoxicity) of once daily vs. twice daily dosing of amikacin in neonates with suspected or proven sepsis and report on the drug’s pharmacokinetics in these subjects. Methods: Thirty neonates of gestational age ≥36 weeks and body weight ≥2500 g with suspected or proven sepsis were randomized to receive amikacin either at a dose of 15 mg/kg once per day; group I (n = 15), or a dose of 7·5 mg/kg twice per day, group II (n = 15). All neonates received classical treatment of sepsis including antibiotics, hemodynamic support, inotropic support based on blood pressure levels and size of the heart in chest X‐ray, if needed. Amikacin was infused over 1 h. Peak and trough serum samples for amikacin were measured for all infants at steady state. Nephrotoxicity was assessed by serum creatinine and urinary N‐acetyl β‐d ‐glucosaminidase before and 7 days after therapy. Clinical efficacy was compared using both observation of clinical status and normalization of laboratory tests. Results: All the patients in group I had achieved a trough level <10 μg/mL and two patients had trough concentration >10 μg/mL in group II. No significant difference between group I and group II in either baseline or day 7 serum creatinine was demonstrated (P > 0·05). No significant difference was found between the two groups in clinical efficacy or renal toxicity. The calculated pharmacokinetic parameters were in group I and II, respectively: clearance =63·8 ± 15·9 mL/kg/h and 73·5 ± 18·1 mL/kg/h; volume of distribution =0·54 ± 0·09 L/kg and 0·61 ± 0·13 L/kg, half‐life =6·1 ± 1·0 h and 5·95 ± 1·1 h. What is new and conclusion: As expected, amikacin given once every 24 h to septic neonates of ≥36 weeks of gestation achieved higher peak levels and lower trough concentrations than the twice daily regimen. Treatment with once daily regimen did not lead to more nephrotoxicity than with a twice‐daily regimen, and showed comparable efficacy.     

Pharmacogenetic determinants for interindividual difference of tacrolimus pharmacokinetics 1 year after renal transplantation

What is known and objective: Tacrolimus, a widely used immunosuppressive agent in organ transplantation, has a narrow therapeutic window. It has been suggested that its interaction with lansoprazole could be dependent on polymorphisms of CYP3A5 and CYP2C19. The objective of this study was to investigate how, 1 year after renal transplantation, CYP3A5 and CYP2C19 polymorphisms, biochemical parameters and coadministration with lansoprazole, influenced tacrolimus pharmacokinetics. Methods: The pharmacokinetics of tacrolimus was studied 1 year after renal transplantation, in 75 recipients who were all receiving continuation treatment with 12‐hourly oral tacrolimus, and 30 mg lansoprazole daily (Group 1; n = 20) or, 10 mg rabeprazole daily or no proton pump inhibitor (Group 2; n = 55). Results: There were no significant differences in the dose‐adjusted area under the plasma concentration–time curve (AUC_0–12) and maximum plasma concentration (C_max) of tacrolimus between CYP2C19 genotype groups, but there were significant differences between CYP3A5 genotypes groups (*1/*1 + *1/*3 vs. *3/*3 = 45·2 ± 20·0 vs. 71·0 ± 34·1 ng·h/mL/mg, P < 0·0001 and 6·3 ± 2·6 vs. 9·3 ± 7·0 ng/mL/mg, P = 0·0017, respectively) and between co‐administration with and without lansoprazole (74·5 ± 34·0 vs. 52·4 ± 27·4 ng·h/mL/mg, P = 0·0054 and 10·9 ± 8·8 vs. 6·7 ± 3·0 ng/mL/mg, P = 0·0024, respectively). In a multiple regression analysis, the dose‐adjusted AUC_0–12 and C_max of tacrolimus were associated with CYP3A5*3/*3 and co‐administration with lansoprazole. What is new and conclusion: CYP2C19 does not seem to contribute to the interaction between tacrolimus and lansoprazole. The long‐term combination of tacrolimus and lansoprazole requires careful monitoring of patients with the CYP3A5*3/*3 genotype.     

Smoking behaviour modulates pharmacokinetics of orally administered clopidogrel

Background and objectives: Clopidogrel is an important antiplatelet drug that is effective in preventing thrombotic events, especially for patients undergoing percutaneous coronary intervention. The therapeutic usefulness of clopidogrel has been limited by documented inter‐individual heterogeneity in platelet inhibition, which may be attributable to known clopidogrel pharmacokinetic variability. The objective of this study was to assess the influence of smoking cigarettes and abnormal body weight on the pharmacokinetics of clopidogrel. Methods: Seventy‐six healthy adult male volunteers were selected randomly. Each subject received a single 75 mg oral dose of clopidogrel after overnight fast. Clopidogrel carboxylate plasma levels were measured and non‐compartmental analysis was used to determine peak plasma concentration (C_max), time to peak plasma concentration (T_max), elimination half‐life (t_1/2e), and area under the curve (AUC_0→∞). Results: One‐third of volunteers were smokers (n = 27) and one‐half had abnormal body weight (n = 39). Smokers had lower AUC_0→∞ (smokers: 6·24 ± 2·32 μg/h/mL vs. non‐smokers: 8·93 ± 3·80 μg/h/mL, P < 0·001) and shorter half‐life (smokers: 5·46 ± 2·99 vs. non‐smokers: 8·43 ± 4·26, P = 0·001). Smoking behaviour had no influence on C_max (P = 0·3) and T_max (P = 0·7). There was no statistically significant difference in C_max, AUC_0→∞, T_max and t_1/2e between volunteers with abnormal body weight and normal body weight. However the difference in body weight of the two groups was relatively narrow (mean ± SE; 26·93 ± 0·16 vs. 23·11 ± 0·27). In general, the pharmacokinetic parameters were characterized by considerable inter‐individual differences (C_max = 3·09 ± 0·99 μg/mL, CV = 32%), (T_max =0·76 ± 0·24 h, CV = 31·6%), (AUC_0→∞ = 7·98 ± 3·58 μg/h/mL, CV = 44·8%), and (t_1/2e = 7·38 ± 4·10 h, CV = 55·6%). Conclusion: Smoking is a significant factor affecting the pharmacokinetics of clopidogrel, following administration of a single 75 mg dose in healthy young volunteers. The study supports smoking‐cessation recommendations. Further studies are required to evaluate the influence of smoking and body weight on the pharmacokinetics of the active metabolite of clopidogrel and on the clinical effects of any differences observed.     

Pharmacokinetics of midazolam tablet in different Chinese ethnic groups

What is known and Objectives: Subjects of different ethnic groups may respond differently to drugs. The present study was conducted to compare the oral pharmacokinetics of midazolam among healthy volunteers from five different ethnic groups in China: Han, Mongolian, Uygur, Hui and Korean. Methods: Healthy volunteers (10 Hans, 10 Mongolians, 10 Uygurs, 10 Huis and 9 Koreans) of Chinese nationality received a single oral tablet dose of 15 mg midazolam in an open label, parallel‐group study. Blood samples were collected at intervals and analysed for midazolam by high performance liquid chromatography (HPLC). Ethnic differences in pharmacokinetic parameters of midazolam using non‐compartmental methods and anova and Kruskal–Wallis rank test. Results and Discussion: Midazolam maximum concentration (C_max) was significantly lower in Mongolians than that in Hans, Uygurs, Huis and Koreans (74·9 ± 33·7, 103·1 ± 26·4, 124·8 ± 50·0, 130·0 ± 38·3 and 189·0 ± 82·1 μg/L, respectively). C_max for the Koreans were significantly greater, compared with Hans and Mongolians. The time to attain C_max (t_max) for Hans was significantly longer as compared with Koreans and Uygurs (1·5 ± 0·7, 0·8 ± 0·5, 0·6 ± 0·7 h, respectively). Midazolam terminal half‐life (t_1/2z) were 3·0 ± 0·8, 2·2 ± 0·7, 1·9 ± 0·7, 3·5 ± 1·9, 3·8 ± 2·3 h for Hans, Mongolians, Uygurs, Huis and Koreans, respectively. The differences in half‐life were significant between Koreans and Mongolians, Koreans and Uygurs, Uygurs and Huis, respectively. There were no differences between young males and females for all pharmacokinetic parameters. Double peaks in the concentration–time profiles were observed in some subjects. What is new and Conclusion: There were some significant differences in midazolam pharmacokinetics between the five Chinese ethnic groups. However, the wide intra‐ethnic variability observed in PK parameters makes predictions of midazolam kinetics, using ethnicity as predictor, unreliable.     

Influence of CYP2C9 and CYP2C19 genetic polymorphisms on pharmacokinetics and pharmacodynamics of gliclazide in healthy Chinese Han volunteers

Background and objective: CYP2C9 is the major contributor to gliclazide metabolic clearance in vitro, while the pharmacokinetics of gliclazide modified release are affected mainly by CYP2C19 genetic polymorphisms in vivo. This study aims to investigate the influence of CYP2C9 and CYP2C19 genetic polymorphisms on the pharmacokinetics and pharmacodynamics of gliclazide in healthy Chinese Han volunteers. Methods: Eighteen healthy Han subjects with various combinations of CYP2C9 and CYP2C19 genotypes received 80 mg gliclazide. Plasma gliclazide concentrations were measured by a liquid chromatography–tandem mass spectrometry method for 84 h and plasma glucose and insulin levels were measured up to 15 h post‐dose. Results and discussion: There was no difference in either pharmacokinetic and or pharmacodynamic parameters of gliclazide when group A (CYP2C9*1/*1, CYP2C19 extensive metabolizers) was compared with group B (CYP2C9*1/*3, CYP2C19 *1/*1). When group C (CYP2C9*1/*1 and CYP2C19 poor metabolizers) was compared with group A, the AUC_0–∞ and C_max in group C were significantly higher [83·94 ± 40·41 vs. 16·39 ± 5·10 μg·h/mL (P = 0·000) and 1·50 ± 0·85 vs. 0·45 ± 0·18 μg/mL (P = 0·000)], and the oral clearance was significantly lower [1·17 ± 0·63 vs. 5·38 ± 1·86 L/h (P = 0·000)]. The half‐life of gliclazide was also significantly prolonged in group C subjects when compared with that of group A (33·47 ± 12·39 vs. 19·34 ± 10·45 h), but the difference was not significant (P = 0·052). The increase in serum glucose level at 11 h after dosing (ΔC_glu11) in group C was significantly higher than that of group A (?1·08 ± 0·42 vs. 0·22 ± 1·01 mmol/L, P = 0·022). The corresponding insulin levels showed no difference between the two groups. Conclusion: CYP2C9*3 was not associated with any change in the disposition of gliclazide. CYP2C19 polymorphisms appear to exert the dominant influence on the pharmacokinetics of gliclazide in healthy Chinese Han subjects, and may also affect the observed pharmacodynamics of the drug as a result.     

Comparison of micafungin and voriconazole in the treatment of invasive fungal infections in kidney transplant recipients

What is known and Objective: Invasive fungal infections are a major threat to renal transplant recipients. Micafungin and voriconazole are two useful antifungal agents for treating such infections. Our objective is to evaluate the comparative efficacy and safety of micafungin and voriconazole in the initial treatment of such infections. Methods: In this prospective, multicentre, open‐labelled, randomized, controlled trial, renal transplant recipients with invasive fungal infections were assigned to receive either micafungin or voriconazole. The enrolled subjects received a kidney transplant between March 2008 and March 2010 at one of the two transplant centres in Henan Province, China. The efficacy and adverse effects of the two treatments were compared. Results and Discussion: The clinical trial enrolled 65 patients, of whom 31 were treated with micafungin, and 34 with voriconazole. The rates of microbiological evidence of infection in the micafungin and voriconazole groups were 64·5% and 70·5%, respectively, whereas the rates of Candida as the major cultured fungus were 80·0% and 75·0%, respectively. Complicated bacterial infection rates in the two treatment groups were 38·7% and 32·4%, respectively, whereas complicated CMV viral infection occurred at a rate of 19·2% and 23·5%, respectively. Fungal infection within one to 3 months after transplant was 83·6% (26/31) and 85·3% (29/34) in the micafungin and voriconazole groups, respectively. There was no significant difference between the two groups in terms of efficacy, survival beyond 10 days and discontinuation of treatment because of lack of efficacy (P > 0·05). Mortality rates in the micafungin and voriconazole groups were 9·7% (3/31) and 12·1% (4/33), respectively. Rates of adverse effects in the two groups were 41·9% and 51·6% (P > 0·05), respectively. What is new and Conclusions: This is the first comparison of micafungin and voriconazole in renal transplant patients. Our study shows that the effectiveness of micafungin was similar to that of voriconazole in such patients.     

Effect of polymerized-type I collagen in knee osteoarthritis. II. In vivo study

Background Polymerized‐Type I Collagen (Polymerized‐Collagen) is an anti‐inflammatory and a tissue regenerator biodrug. The aim of the study was to evaluate the efficacy and safety of intra‐articular injections of Polymerized‐Collagen in patients with knee osteoarthritis (OA). Methods and design Patients (n = 53) were treated with 12 intra‐articular injections of 2 mL of Polymerized‐Collagen (n = 27) or 2 mL of placebo (n = 26) during 6 months. Follow up period was 6 months. The primary endpoints included Western Ontario and McMaster University Osteoarthritis Index, Lequesne index, and pain intensity on a visual analogue scale (VAS). Secondary outcomes were patient global score, investigator global score and drug evaluation. Clinical improvement was determined if the decrease in pain exceeds 20 mm on a VAS and patients achieved at least 20% of improvement from baseline. Urinary levels of C‐terminal crosslinking telopeptide of collagen type II (CTXII) and serum high‐sensitivity C‐reactive protein (hsCRP) were determined by enzyme immunoassays. Statistical analysis was performed by intention to treat. Results Polymerized‐Collagen was safe and well tolerated. Patients had a statistically significant improvement (P < 0·05) from baseline vs. Polymerized‐Collagen and vs. placebo at 6 months in: Lequesne Index (13·1 ± 0·5 vs. 7·1 ± 0·7 vs. 9·6 ± 0·8; P = 0·027), WOMAC (9·0 ± 0·5 vs. 4·0 ± 0·6 vs. 5·80 ± 0·8; P = 0·032), patient VAS (60·0 ± 2·6 vs. 20·6 ± 2·4 vs. 36·1 ± 4·5; P = 0·003), physician VAS (49·8 ± 1·9 vs. 16·8 ± 2·9 vs. 29·8 ± 2·9; P = 0·002), patient global score (1·08 ± 0·1 vs. 2·7 ± 0·1 vs. 1·9 ± 0·2; P = 0·028) and analgesic usage (30·1 ± 9·4 vs. 11·0 ± 3·4 vs. 17·9 ± 4·9; P = 0·001). This improvement was persistent during the follow up. A threefold increase in CTXII was determined in placebo group. No differences were found on hs CRP and incidence of adverse events between groups. Conclusion Polymerized‐Collagen is safe and effective in the treatment of knee OA.     

Population pharmacokinetics of steady-state carbamazepine in Egyptian epilepsy patients

What is Known and Objective: Individualization of carbamazepine (CBZ) dosage regimen in patients with epilepsy based on based on therapeutic drug monitoring (TDM) followed by estimation of pharmacokinetic (PK) parameters can help in better control of epilepsy. Our objective was to establish a population (POP) PK model of CBZ for Egyptian adult and pediatric patients with epilepsy. Method: Single steady‐state (SS) trough plasma concentrations of CBZ were available for 302 patients with epilepsy (55·6% men and 44·4% women) who were categorized as children (n = 118) and adults (n = 184) with mean age (years) ± SD of 10·6 ± 4·8 and 29·4 ± 9·9, respectively. Carbamazepine was given as an oral suspension (n = 19) or controlled release tablet (n = 283) with average dose of 15·0 ± 7·8 mg/kg per day. A one‐compartment model with first‐order absorption and elimination for SS conditions (ADVAN2, SS2, TRANS2) was applied using NONMEM 6.2. Separate absorption rate constants were modelled for the two formulations. The mean POP CL, its intersubject variability (ISV), as well as residual error of CBZ concentration were estimated. Results and Discussion: The POP estimate for CL was 3·5 L/h with coefficient of variation value of 2·6%, which was consistent with literature data. The ISV on CL was 44·5%. The POP PK model was validated by bootstrap re‐sampling, and the individual estimates were within the 95% CI of the bootstrap results. Different covariates that might affect CBZ CL have been evaluated but the limited number of samples per individual prevented precise covariate analysis. What is New and Conclusion: The POP PK model we have developed for CBZ shows good predictive performance in Egyptian adult and pediatric patients with epilepsy. Another PK study to better define the effect of different covariates would improve on the model for dosage individualization.     

Ammonia uptake by skeletal muscle in the hyperammonaemic rat

Abstract. A two-stage surgical occlusion of the portal vein was employed to produce hyperammonaemia in the rat. The procedure resulted in a significant rise of arterial blood ammonia level from 70·5 ± 6·5 μmol/l (mean ± SEM, n= 10) to 214·0 ± 37·7 μmol/l and in a rise of venous blood ammonia from 65·0 ± 9·4 μmol/l to 122·2 ± 7·4 μmol/l during the first day following the complete vein occlusion. A marked increase of the arteriovenous difference of ammonia concentration from virtually zero in sham-operated controls to 72 ± 9 (n= 8) μmol/l in rats 1 day after the surgical manipulation suggested uptake of ammonia by skeletal muscle. Rat muscle glutamine synthetase activity increased from 0·46 ± 0·06 u/mg (n= 7) in controls to 2·7 ± 0·3 u/mg (n= 7) on the fourth day following portal vein ligation, and muscle branched chain amino acids aminotransferase increased from 0·2 ± 0·05 u/mg in controls to 0·96 ± 0·1 u/mg (n= 7) during the first day of ligation. Glutamine dehydrogenase and aspartate aminotransferase activities were not affected by the surgical procedure. These observations suggest that ammonia trapping in skeletal muscle is coupled to glutamine formation via amination of glutamic acid. This conclusion was further supported by the finding that ammonia uptake correlated (r= 0·92) with enahnced release of glutamine from muscle and that treatment with methionine sulfoximine, a potent inhibitor of glutamine synthetase, changed the arteriovenous difference of glutamine from –0·92 ± 0·01 mmol/l in ligated animals (net release) to ± 0·12 ± 0·01 mmol/l (net uptake) in ligated and inhibitor-treated animals. Similarly, the inhibitor also abolished the arterio-venous difference of ammonia. Thus, the animal model of hyperammonaemia and the muscle enzyme assays reveal that skeletal muscle is involved in the regulation of blood ammonia level by conversion of ammonia, via glutamic acid, to glutamine.     

The pathophysiology of the insulin-like growth factor axis in fetal growth failure: a basis for programming by undernutrition?

Abstract. Recent evidence suggests that a number of adulthood conditions, including non-insulin dependent diabetes mellitus (NIDDM) and lipid and cardiovascular abnormalities are associated with intra-uterine growth retardation (IUGR). It is possible that this arises from programming of endocrine axes during development as a result of an adverse intra-uterine environment. Insulin-like growth factors (IGFs) are mitogenic polypeptides which stimulate cellular proliferation and differentiation and are important in human fetal development. The functions of IGFs are modulated by specific high affinity binding proteins (IGFBPs). IGFBP-1 is antagonistic to the insulin-like and growth promoting effects of IGF-I, and IGFBP-3 holds IGFs in the circulation by associating with IGFs and an acid labile subunit to form a ternary complex. Using specific radioimmunoassays and fetal serum obtained during diagnostic cordocentesis we have investigated the role of the IGF/IGFBP axis in human fetal development. In a study of 130 singleton pregnancies we have examined levels of immunoreactive IGFs and IGFBPs in normally grown fetuses (AGA), starved small fetuses affected by uteroplacental insufficiency (UPI), and non-starved small fetuses (SGA). IGF-1 was significantly lower in the UPI group (n= 14, 7·8±0·6 μg l^-1), than in either the SGA group (n= 22, 31·4±3·5 μg l^-1, P= 0·0001) or the AGA group (n= 94, 36·3±1·9 μg l^-1, P= 0·0001). IGFBP-3 showed similar changes (UPI: 682·6±50·0 μg l^-1; SGA: 831·9±55·5 μg l^-1; AGA: 847·7±19·8 μg l^-1). In contrast, IGFBP-1 levels were significantly higher in the UPI group (312·4±57·5 μg l^-1) than in either the SGA group (132·6±39·5 μg l^-1, P= 0·009) or the AGA group (116·9±25·4 μg l^-1, P= 0·003), and the normal inverse relationship between IGFBP-1 and insulin levels was lost in the UPI group. IGFBP-2 levels showed a similar pattern (UPI: 2510·3±178·0 μg l^-1; SGA: 878·5±80·3μg l^-1, P= 0·0001; AGA: 791·6±27·0 μg l^-1, P= 0·0001). Thus, there are clear differences between the two groups of SGA fetuses. It is possible that in utero‘programming’ of the IGF/IGFBP axis, as a result of fetal undernutrition, may be important in the pathogenesis of disease in adulthood.     

Cyclosporine alters correlation between free and total mycophenolic acid in kidney transplant recipients in the initial phase

What is known and Objective: The factors affecting the pharmacokinetics of free mycophenolic acid (MPA) and its phenolic glucuronide (MPAG) are still unclear. The aim of this study was to evaluate the influence of cyclosporine on the pharmacokinetics of free MPA and MPAG. Methods: Seventy‐seven kidney transplant recipients (23 were in an initial phase and 54 in a stable phase; 41 were treated with cyclosporine and 36 with tacrolimus) were enrolled. Free and total MPA and MPAG were determined using HPLC. The correlations between free and total predose concentrations (C₀) of MPA or MPAG were evaluated separately in patients receiving calcineurin inhibitor medications. Results and Discussion: Serum concentration of albumin was lower in the initial phase than in the stable phase. A higher ratio of free MPAG C₀ to free MPA C₀ was observed in cyclosporine‐treated than tacrolimus‐treated kidney transplant recipients. Free MPA C₀ correlated weakly with total MPA C₀ in kidney transplant recipients treated with cyclosporine in the initial phase (ρ = 0·53, P = 0·06). What is new and Conclusion: Cyclosporine increased the ratio of free MPAG C₀ to free MPA C₀ and varied the free fraction of MPA in the hypoalbuminaemic kidney transplant recipients in the initial phase.     

Effects of intense exercise training on endothelium-dependent exercise-induced vasodilatation

To determine whether intense exercise training affects exercise-induced vasodilatation, six subjects underwent 4 weeks of handgrip training at 70% of maximal voluntary contraction. Exercise forearm vascular conductance (FVC) responses to an endothelium-dependent vasodilator (acetylcholine, ACH; 15, 30, 60 μg min^?1) and an endothelium-independent vasodilator (sodium nitroprusside, SNP; 1·6, 3·2, 6·4 μg min^?1) and FVC after 10 min of forearm ischaemia were determined before and after training. Training elicited significant (P<0·001) increases in grip strength (43·4 ± 2·3 vs. 64·1 ± 3·5 kg, before vs. after, mean ± SEM), forearm circumference (26·7 ± 0·4 vs. 27·9 ± 0·4 cm) and maximal FVC (0·4630 ± 0·0387 vs. 0.6258 ± 0·0389 units, P<0·05). Resting FVC did not change significantly with training (0·0723 ± 0·0162 vs. 0.0985 ± 0·0171 units, P>0·4), but exercise FVC increased (0·1330 ± 0·0190 vs. 0.2534 ± 0·0387 units, P<0·05). Before and after the training, ACH increased exercise FVC above the control (no drug) exercise FVC, whereas SNP did not. Training increased (P<0·05) the exercise FVC responses to ACH (0·3344 ± 0·1208 vs. 0.4303 ± 0·0858 units, before vs. after training, 60 μg min^?1) and SNP (0·2066 ± 0·0849 vs. 0.3172 ± 0·0628 units, 6·4 μg min^?1). However, these increases were due to the increase in control (no drug) exercise FVC, as the drug-associated increase in exercise FVC above control did not differ between trials (P>0·6). These results suggest that exercise FVC is increased by both exercise training and stimulating the release of endothelium-dependent vasodilators. However, training does not affect the vascular response to these vasodilators.     

Skeletal muscle analyses: agreement between non‐contrast and contrast CT scan measurements of skeletal muscle area and mean muscle attenuation

Low skeletal muscle area (SMA) and muscle radiation attenuation (MRA) have been associated with poor prognosis in various patient populations. Both non‐contrast and contrast CT scans are used to determine SMA and MRA. The effect of the use of a contrast agent on SMA and MRA is unknown. Therefore, we investigated agreement between these two scan options. SMA and MRA of 41 healthy individuals were analysed on a paired non‐contrast and contrast single CT scan, and agreement between paired scan results was assessed with use of Bland–Altman plots, intraclass correlation coefficients (ICCs), standard error of measurements (SEM) and smallest detectable differences at a 95% confidence level (SDD₉₅). Analyses were stratified by tube voltage. Difference in SMA between non‐contrast and contrast scans made with a different tube voltage was 7·0 ± 7·5 cm²; for scans made with the same tube voltage this was 2·3 ± 1·7 cm². Agreement was excellent for both methods: ICC: 0·952, SEM: 7·2 cm², SDD₉₅: 19·9 cm² and ICC: 0·997, SEM: 2·0 cm², SDD₉₅: 5·6 cm², respectively. MRA of scans made with a different tube voltage differed 1·3 ± 11·3 HU, and agreement was poor (ICC: 0·207, SEM: 7·9 HU, SDD₉₅: 21·8 HU). For scans made with the same tube voltage the difference was 6·7 ± 3·2 HU, and agreement was good (ICC: 0·682, SEM: 5·3 HU, SDD₉₅: 14·6 HU). In conclusion, SMA and MRA can be slightly influenced by the use of contrast agent. To minimise measurement error, image acquisition parameters of the scans should be similar.     

Effect of telmisartan, valsartan and candesartan on mycophenolate mofetil pharmacokinetics in Japanese renal transplant recipients

Objective: The aim of this study was to elucidate the effect of the peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) activating angiotensin receptor blocker (ARB) telmisartan and the non‐PPAR‐γ activating ARB valsartan and candesartan on mycophenolic acid (MPA) pharmacokinetics in renal transplant recipients. Methods: Recipients (n = 10 each group) were randomly given either 40 mg of telmisartan, 80 mg of valsartan or 8 mg of candesartan cilexetil for at least 6 months, and no ARB. Blood was sampled a year after transplantation. Results: Dose‐adjusted maximum and trough plasma concentration of MPA co‐administered with telmisartan were the lowest in all groups. The mean dose‐adjusted area under the concentration curve from 0 to 12 h (AUC_0–12) and AUC_0–6 of MPA co‐administered with telmisartan were significantly lower than that without ARB (98 vs. 138 ng·h/mL/mg, P = 0·0353 and 63 vs. 96 ng·h/mL/mg, P = 0·0305). Coadministration of valsartan and candesartan did not alter MPA pharmacokinetics. The AUC ratio of MPA glucuronide (MPAG)/MPA co‐administered with telmisartan was higher than that without ARBs, but not significantly (14·2 vs. 9·1). The mean maximum and minimum plasma concentrations of telmisartan (40 mg) after oral administration were 84 and 15 ng/mL, respectively, and that of valsartan (80 mg) 2220 and 441 ng/mL, respectively. Plasma concentrations of candesartan in most transplant patients were not observed 19 h after oral administration of candesartan cilexeil (8 mg). Conclusions: The degree of drug interaction between MPA and telmisartan was significantly greater than that between MPA and valsartan or candesartan. Uridine diphosphate‐glucuronosyltransferase (UGT) 1A9 has been identified as a PPAR‐γ target gene. UGT induction by telmisartan might stimulate MPA glucuronidation. A combination of telmisartan and mycophenolate mofetil might require periodic monitoring of MPA.