Pharmacokinetics of enteric-coated cysteamine bitartrate in healthy adults: a pilot study

AIMS

Cysteamine bitartrate (Cystagon®) is the approved treatment for cystinosis. Poor compliance and patient outcome may occur because the drug needs to be taken every 6 h and in some patients causes gastrointestinal symptoms due to hypergastrinaemia. A formulation of cysteamine requiring twice daily ingestion would improve the quality of life for these patients. This study compares the pharmacokinetics and gastrin production following cysteamine bitartrate non-enteric-coated and cysteamine bitartrate enteric-coated in normal healthy subjects.

METHODS

Enteric-coated cysteamine was prepared. Following single doses of cysteamine bitartrate non-enteric-coated 450 mg and cysteamine bitartrate enteric-coated 450 mg and 900 mg, serial plasma cysteamine and gastrin concentrations were measured. Two subjects also received cysteamine bitartrate non-enteric-coated 900 mg. Gastrointestinal (GI) symptoms were recorded.

RESULTS

Six healthy adults (mean age 20.7 years, range 18–24 years; mean weight 59.3 kg) received drug. All post-dose gastrin concentrations were within the normal range (<100 pg ml^–1). The t_max following cysteamine bitartrate non-enteric-coated (mean and SD is 75 ± 19 min) was shorter than cysteamine bitartrate enteric-coated (220 ± 74 min) (P = 0.001), but only the C_max and AUC estimates following 900 mg cysteamine bitartrate enteric-coated were significantly greater than any of the other preparations or doses (P < 0.05). One patient had GI symptoms following both 900 mg cysteamine bitartrate non-enteric-coated and cysteamine bitartrate enteric-coated.

CONCLUSION

Although patient numbers were low, single high doses of cysteamine bitartrate enteric-coated were better tolerated than similar doses of cysteamine bitartrate non-enteric-coated in the healthy subjects and all had normal gastrin concentrations. The delayed t_max following cysteamine bitartrate enteric-coated suggested that the cysteamine was released enterically.     

Evaluation of clinical activity and safety of Daflon 500 mg in type 2 diabetic female patients

Background

The incidence of cardiovascular disease in patients with type 2 diabetes mellitus is approximately twice as high as in the non-diabetic population.

Aim

To investigate the hypoglycemic and hypocholesterolemic effects of Daflon^® 500 mg (DF) administration together with its tolerability and efficacy in reducing the cardiovascular metabolic risk factors in female patients with type 2 diabetes.

Methods

In a well-adequate controlled single-blinded randomized parallel design the tolerability and the efficacy of Daflon^® (500 mg) either alone or with oral hypoglycemic, twice daily for 45 days, was studied in 36 female patients with type 2 diabetes.

Results

None of the patients in the studied groups were reported to have any adverse events throughout the treatment period (45 days), liver and kidney function tests were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 45) values. Female patients receiving Daflon^® either alone or with oral hypoglycemic showed significant decrease in serum glucose; fructosamine; total cholesterol; LDL–cholesterol; triglycerides; malondialdehydes (as index of lipid peroxidation) and C-reactive protein (CRB) levels along with increase in the levels of nitric oxide and blood glutathione.

Conclusion

This study has shown that Daflon^® (500 mg, twice daily for 45 days) is helpful in reducing glucose level and the risk of cardiovascular disease in type 2 diabetic patients.

Recommendation

Further clinical trials are essential for strengthening the evidence base on the role of this drug in the cardiovascular risk in diabetic patients.     

The effect of semelil (angipars?) on bone resorption and bone formation markers in type 2 diabetic patients

Background and purpose of the study

Diabetes mellitus has been recognized as a major risk factor for osteoporosis in which bone turnover is affected by different mechanisms. As the morbidity, mortality and financial cost related to osteoporosis are expected to rise in Iran in coming years, and considering the efficacy of Angipars® for improvement of different ulcers which made it a new herbal drug in diabetic foot ulcer, there is a need to evaluate the effect of this new drug on different organs including bone resorption and bone formation markers.

Methods

In this randomized, double- blind clinical trial, 61 diabetic patients were included. The subjects were randomly divided into intervention and control groups. Subjects of intervention group received 100 mg of Angipars® twice a day. Laboratory tests including bone resorption and bone formation markers were performed at baseline and after 3 months.

Result

31 patients in study group and 30 patients in control group finished the study. The mean age of the study population and the mean disease duration was respectively 51.8 ± 6.2 and 7.5 ± 4.7 years with no significant differences between intervention and control patients. No statistically significant differences between patients and controls were observed in pyridinoline, osteocalcin, urine calcium, bone alkaline phosphatase and tumor necrosis factor (TNF-α). Only urine creatinine level significantly changed between two groups after 3 month of treatment (p-value: 0.029)

Conclusion

In conclusion, the findings of this study indicate that Semelil (Angipars®) had no beneficial or harmful effects on bone. It might be other effects of this new component on bone turnover process which need more studies and more time to be discovered.     

Oral bioavailability of dabigatran etexilate (Pradaxa?) after co-medication with verapamil in healthy subjects

Aim

To investigate the effect of the P-glycoprotein inhibitor verapamil on the pharmacokinetics and pharmacodynamics of dabigatran etexilate (DE).

Method

In this two part multiple crossover trial in 40 healthy subjects, DE 150 mg was given alone or with verapamil at different doses, duration of treatment (single vs. multiple dosing), formulations, and timings (before, concurrently or after DE). Primary pharmacokinetic endpoints were determined from concentrations of total dabigatran (unconjugated plus conjugated). Pharmacodynamic endpoints were determined from clotting time.

Results

The greatest effect was observed with single dose verapamil 120 mg immediate release given 1 h before single dose DE. Geometric mean area under the plasma concentration curve [AUC(0,∞)] and maximum analyte concentration in the plasma (C_max) were increased by 143% [90% confidence interval (CI) 91, 208] and 179% (90% CI 115, 262), respectively. The effect was reduced to a 71% and 91% increase in AUC and C_max, respectively, when DE was administered with verapamil 240 mg extended release. After multiple verapamil dosing, DE AUC(0,∞) and C_max increases were 54% and 63%, respectively. However, DE given 2 h before verapamil increased DE AUC(0,∞) and C_max by <20%. With regard to clotting prolongation, the dabigatran plasma concentration–effect relationship was generally not affected by the co-administration of verapamil. Concomitant administration of DE and verapamil did not reveal any unexpected safety findings.

Conclusion

Verapamil increased DE bioavailability, likely due to inhibition of P-glycoprotein. Our results suggest that an interaction between verapamil and DE can be minimized if DE is administered 2 h prior to verapamil.     

Population pharmacokinetics and maximum a posteriori probability Bayesian estimator of abacavir: application of individualized therapy in HIV-infected infants and toddlers

AIMS

To develop a population pharmacokinetic model for abacavir in HIV-infected infants and toddlers, which will be used to describe both once and twice daily pharmacokinetic profiles, identify covariates that explain variability and propose optimal time points to optimize the area under the concentration–time curve (AUC) targeted dosage and individualize therapy.

METHODS

The pharmacokinetics of abacavir was described with plasma concentrations from 23 patients using nonlinear mixed-effects modelling (NONMEM) software. A two-compartment model with first-order absorption and elimination was developed. The final model was validated using bootstrap, visual predictive check and normalized prediction distribution errors. The Bayesian estimator was validated using the cross-validation and simulation–estimation method.

RESULTS

The typical population pharmacokinetic parameters and relative standard errors (RSE) were apparent systemic clearance (CL) 13.4 l h⁻¹ (RSE 6.3%), apparent central volume of distribution 4.94 l (RSE 28.7%), apparent peripheral volume of distribution 8.12 l (RSE14.2%), apparent intercompartment clearance 1.25 l h⁻¹ (RSE 16.9%) and absorption rate constant 0.758 h⁻¹ (RSE 5.8%). The covariate analysis identified weight as the individual factor influencing the apparent oral clearance: CL = 13.4 × (weight/12)^1.14. The maximum a posteriori probability Bayesian estimator, based on three concentrations measured at 0, 1 or 2, and 3 h after drug intake allowed predicting individual AUC_0–t.

CONCLUSIONS

The population pharmacokinetic model developed for abacavir in HIV-infected infants and toddlers accurately described both once and twice daily pharmacokinetic profiles. The maximum a posteriori probability Bayesian estimator of AUC_0–t was developed from the final model and can be used routinely to optimize individual dosing.     

Pharmacokinetics and pharmacodynamics of liposomal mifamurtide in adult volunteers with mild or moderate renal impairment

Aims

To evaluate the pharmacokinetics and pharmacodynamics following a single dose of liposomal mifamurtide (L-MTP-PE, MEPACT®) in adult subjects with mild (calculated creatinine clearance [CL_cr] of 50–80 ml min⁻¹) or moderate (CL_cr 30–50 ml min⁻¹) renal impairment in comparison with age-, weight- and gender-matched healthy subjects with normal renal function (CL_cr >80 ml min⁻¹).

Methods

Subjects received a 4 mg dose of liposomal mifamurtide via 1 h intravenous infusion. Blood samples were collected over 72 h for analysis of plasma pharmacokinetics of total and non-liposome-associated (free) mifamurtide and assessment of pharmacodynamics (changes in serum interleukin-6 [IL-6], tumour necrosis factor-α [TNF-α], C-reactive protein [CRP]).

Results

Thirty-three subjects were enrolled: nine with mild renal impairment, eight with moderate renal impairment and 16 healthy subjects. Geometric mean (%CV) AUC_inf for total mifamurtide was 89.5 (58.1), 94.8 (27.8), 85.1 (29.0), 95.4 (18.1) nm h in the mild renal impairment, mild-matched healthy subject, moderate renal impairment and moderate-matched healthy subject groups, respectively. Mifamurtide clearance was not correlated with CL_cr, estimated glomerular filtration rate or iohexol clearance (all r² < 0.01). AUC_inf of free mifamurtide was similar across the renal function groups. There were no readily apparent differences in serum pharmacodynamic effect parameters (baseline-adjusted AUEC_last for IL-6 and TNF-α and E_max for CRP) between the renal function groups. No subjects reported grade ≥3 or serious adverse events.

Conclusions

Mild or moderate renal impairment does not alter the clinical pharmacokinetics or pharmacodynamics of mifamurtide. No dose modifications appear necessary for these patients based on clinical pharmacologic considerations.     

Bioavailability and disposition of azelastine and fluticasone propionate when delivered by MP29-02, a novel aqueous nasal spray

AIM(S)

To determine azelastine hydrochloride (AZE) and fluticasone propionate (FP) bioavailabilities of the novel nasal spray combination product MP 29-02, compared with MP29-02-based products containing only AZE (MP29-02-AZE-mono), FP (MP29-02-FP-mono), marketed AZE and FP single entity products (Astelin® and FP Boehringer-Ingelheim; FP-BI).

METHODS

Two randomized, three period, six sequence, three treatment crossover studies were conducted in healthy subjects. Study 1 administered 200 µg FP as MP29-02, MP29-02-FP-mono or FP-BI. Study 2 administered 548 µg AZE as MP29-02, MP29-02-AZE-mono or Astelin®. Each dose consisted of two sprays/nostril. Serum FP and plasma AZE were followed over 24 (FP) and 120 h (AZE) and quantified by LC-MS/MS. Peak (C_max) and total exposures AUC(0,t_last) were compared between the treatments by anova.

RESULTS

Study 1: Average FP C_max was very low with all products (≤10 pg ml⁻¹). FP AUC(0,t_last) point estimates (90% CIs) for MP29-02 : MP29-02-FP-mono and MP29-02 : FP-BI ratios (%) were 93.6 (83.6, 104.7) and 161.1 (137.1, 189.3). Corresponding ratios for C_max were 91.0 (82.5, 100.4) and 157.4 (132.5, 187.1). Study 2: AZE AUC(0,t_last) point estimates (90% CIs) for MP29-02 : MP29-02-AZE-mono and MP29-02 : Astelin® ratios (%) were 98.8 (91.0, 107.4) and 105.5 (95.6, 116.4). Corresponding outcomes for C_max were 102.7 (92.1, 114.4) and 107.3 (92.6, 124.3).

CONCLUSIONS

No interactions of AZE and FP were found with the MP29-02 formulation. Azelastine bioavailability was similar for MP29-02 and Astelin®. Maximum and total FP exposure was higher for MP29-02-based products compared with FP-BI. FP concentrations were generally very low with all investigational products and did not suggest clinically meaningful differences concerning systemic safety.     

Pharmacokinetics and pharmacodynamics of liposomal mifamurtide in adult volunteers with mild or moderate hepatic impairment

Aims

To evaluate the pharmacokinetics and pharmacodynamics after a single dose of liposomal mifamurtide (liposomal muramyl tripeptide phospatidyl ethanolamine; MEPACT®) in adult subjects with mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment in comparison with age-, weight- and sex-matched healthy subjects with normal hepatic function.

Methods

Subjects received a 4 mg dose of liposomal mifamurtide via 1 h intravenous infusion. Blood samples were collected over 72 h for pharmacokinetic and pharmacodynamic assessments (changes in serum interleukin-6, tumour necrosis factor-α and C-reactive protein).

Results

Thirty-seven subjects were enrolled: nine with mild hepatic impairment, eight with moderate hepatic impairment and 20 matched healthy subjects. Geometric least-square mean ratios of total mifamurtide AUC_inf for the mild hepatic impairment and moderate hepatic impairment groups vs. matched healthy subjects were 105% (90% confidence interval, 83.6–132%) and 119% (90% confidence interval, 94.1–151%), respectively, which are below the protocol-specified threshold (150%) to require development of dose-modification recommendations. Pharmacodynamic parameters for changes in serum interleukin-6 and tumour necrosis factor-α concentrations were generally similar across hepatic function groups. Mifamurtide-induced increases in serum C-reactive protein were attenuated in the moderate hepatic impairment group, consistent with the liver being the major organ of C-reactive protein synthesis. No grade ≥3 adverse events were seen in subjects administered mifamurtide (4 mg).

Conclusions

These results support the conclusion that mild or moderate hepatic impairment does not produce clinically meaningful effects on the clinical pharmacokinetics or pharmacodynamics of mifamurtide; no dose modifications are needed in these special patient populations based on clinical pharmacological considerations.     

Efficacy and safety of Iranian made Deferasirox (Osveral®) in Iranian major thalassemic patients with transfusional iron overload: A one year prospective multicentric open-label non-comparative study

Purpose of the study

to determine the efficacy, adverse effects and safety of a new Iranian generic product of deferasirox (Osveral®) in Iranian transfusion dependent major thalassemic (TD-MT) patients.

Methods

In 9 main thalassemia treatment centers, all of TD-MT patients (aged ≥2 yrs) with serum ferritin (SF) levels≥1000 ng/ml, or >100 ml/kg of RBC transfusion,who could not tolerate parental iron chelating were recruited regardless of their previous iron chelation therapy. Periodical clinical and laboratory evaluations were conducted for adverse effects (AEs). Primary efficacy end point was Mean of Relative Change of Serum Ferritin (MRC-SF) from the baseline level during one year. Analysis of variance (ANOVA), t test, chi-square or Fisher exact test were used for statistic analysis appropriately (P values <0.05 were considered as statistical significant).

Results

In 407 cases the male/female ratio was 0.98. Mean age was 11.5±7.4 (2–58) years. The mean of initiating dose of Osveral® and mean usage dose during the study was 23.5±4.9 mg/kg and 24.9±4.9 mg/kg respectively. MRC-SF was −11.44% ±38.92 and it showed significant decline in SF (P value<0.001) one hundred and forty eight patients out of 407 patients experienced at least one. AE, the most common of them were transient increase in serum creatinin (97;24.1%) and>5 time increase in transaminases (24;5.89%).The causes of discontinuation of treatment were non-satisfactory treatment ( 24; 5.8%), poor or non-compliance of patients (21;5.1%), and adverse effects (13; 3.1%)

Conclusion

A detailed comparison with similar studies on deferasirox (Exjade®) shows a promising efficacy and safety for its Iranian generic product (Osveral ®).     

Pharmacokinetic tools for the dose adjustment of ciclosporin in haematopoietic stem cell transplant patients

Aims

Ciclosporin A (CsA) is used in the prophylaxis and treatment of acute and chronic graft vs. host disease after haematopoietic stem cell (HSCT) transplantation. Our objective was to build and compare three independent Bayesian estimators of CsA area under the curve (AUC) using a limited sampling strategy (LSS), to assist in dose adjustment.

Methods

The Bayesian estimators were developed using in parallel: two independent parametric modelling approaches (nonmem® and iterative two stage (ITS) Bayesian modelling) and the non-parametric adaptive grid method (Pmetrics®). Seventy-two full pharmacokinetic profiles (at pre-dose and 0.33, 0.66, 1, 2, 3, 4, 6, 8 and 12h after dosing) collected from 40 HSCT patients given CsA were used to build the pharmacokinetic models, while 15 other profiles (n = 7) were kept for validation. For each Bayesian estimator, AUCs estimated using the full profiles were compared with AUCs estimated using three samples.

Results

The pharmacokinetic profiles were well fitted using a two compartment model with first order elimination, combined with a gamma function for the absorption phase with ITS and Pmetrics or an Erlang distribution with nonmem. The derived Bayesian estimators based on a C0-C1 h-C4 h sampling schedule (best LSS) accurately estimated CsA AUC(0,12 h) in the validation group (n = 15; nonmem: bias (mean ± SD)/RMSE 2.05% ± 13.31%/13.02%; ITS: 4.61% ± 10.56%/11.20%; Pmetrics: 0.30% ± 10.12%/10.47%). The dose chosen confronting the three results led to a pertinent dose proposal.

Conclusions

The developed Bayesian estimators were all able to predict ciclosporin AUC(0,12 h) in HSCT patients using only three blood with minimal bias and may be combined to increase the reliability of CsA dose adjustment in routine.     

Population pharmacokinetics of mycophenolic acid and dose optimization with limited sampling strategy in liver transplant children

AIMS

The aims were to estimate the mycophenolic acid (MPA) population pharmacokinetic parameters in paediatric liver transplant recipients, to identify the factors affecting MPA pharmacokinetics and to develop a limited sampling strategy to estimate individual MPA AUC(0,12 h).

METHODS

Twenty-eight children, 1.1 to 18.0 years old, received oral mycophenolate mofetil (MMF) therapy combined with either tacrolimus (n= 23) or ciclosporin (n= 5). The population parameters were estimated from a model-building set of 16 intensive pharmacokinetic datasets obtained from 16 children. The data were analyzed by nonlinear mixed effect modelling, using a one compartment model with first order absorption and first order elimination and random effects on the absorption rate (k_a), the apparent volume of distribution (V/F) and apparent clearance (CL/F).

RESULTS

Two covariates, time since transplantation (≤ and >6 months) and age affected MPA pharmacokinetics. k_a, estimated at 1.7 h⁻¹ at age 8.7 years, exhibited large interindividual variability (308%). V/F, estimated at 64.7 l, increased about 2.3 times in children during the immediate post transplantation period. This increase was due to the increase in the unbound MPA fraction caused by the low albumin concentration. CL/F was estimated at 12.7 l h⁻¹. To estimate individual AUC(0,12 h), the pharmacokinetic parameters obtained with the final model, including covariates, were coded in Adapt II® software, using the Bayesian approach. The AUC(0,12 h) estimated from concentrations measured 0, 1 and 4 h after administration of MMF did not differ from reference values.

CONCLUSIONS

This study allowed the estimation of the population pharmacokinetic MPA parameters. A simple sampling procedure is suggested to help to optimize pediatric patient care.     

Grapefruit juice markedly increases the plasma concentrations and antiplatelet effects of ticagrelor in healthy subjects

Aim

This study examined the effects of grapefruit juice on the new P2Y₁₂ inhibitor ticagrelor, which is a substrate of CYP3A4 and P-glycoprotein.

Methods

In a randomized crossover study, 10 healthy volunteers ingested 200 ml of grapefruit juice or water thrice daily for 4 days. On day 3, they ingested a single 90 mg dose of ticagrelor.

Results

Grapefruit juice increased ticagrelor geometric mean peak plasma concentration (C_max) to 165% (95% confidence interval 147, 184%) and area under the concentration–time curve (AUC(0,∞)) to 221% of control (95% confidence interval 200, 245%). The C_max and AUC(0,34 h) (P < 0.05) but not the AUC(0,∞) of the active metabolite C12490XX were decreased significantly. Grapefruit juice had a minor effect on ticagrelor elimination half-life prolonging it from 6.7 to 7.2 h (P = 0.036). In good correlation with the elevated plasma ticagrelor concentrations, grapefruit juice enhanced the antiplatelet effect of ticagrelor, assessed with VerifyNow® and Multiplate® methods, and postponed the recovery of platelet reactivity.

Conclusions

Grapefruit juice increased ticagrelor exposure by more than two-fold, leading to an enhanced and prolonged ticagrelor antiplatelet effect. The grapefruit juice–ticagrelor interaction seems clinically important and indicates the significance of intestinal metabolism to ticagrelor pharmacokinetics.     

Population pharmacokinetic analysis of tacrolimus in Mexican paediatric renal transplant patients: role of CYP3A5 genotype and formulation

Aims

The aims of this study were (i) to develop a population pharmacokinetic (PK) model of tacrolimus in a Mexican renal transplant paediatric population (n = 53) and (ii) to test the influence of different covariates on its PK properties to facilitate dose individualization.

Methods

Population PK and variability parameters were estimated from whole blood drug concentration profiles obtained at steady-state using the non-linear mixed effect modelling software NONMEM® Version 7.2.

Results

Tacrolimus PK profiles exhibited high inter-patient variability (IPV). A two compartment model with first order input and elimination described the tacrolimus PK profiles in the studied population. The relationship between CYP3A5 genotype and tacrolimus CL/F was included in the final model. CL/F in CYP3A5*1/*1 and *1/*3 carriers was approximately 2- and 1.5-fold higher than in CYP3A5*3/*3 carriers (non-expressers), respectively, and explained almost the entire IPV in CL/F. Other covariates retained in the final model were the tacrolimus dose and formulation type. Limustin® showed markedly lower concentrations than the rest of the formulations.

Conclusions

Population PK modelling of tacrolimus in paediatric renal transplant recipients identified the tacrolimus formulation type as a significant covariate affecting the blood concentrations and confirmed the previously reported significant effect of CYP3A5 genotype on CL/F. It allowed the design of a proposed dosage based on the final model that is expected to help to improve tacrolimus dosing.     

Population pharmacokinetics and Bayesian estimation of tacrolimus exposure in paediatric liver transplant recipients

Aims

The objectives of this study were to develop a population pharmacokinetic (PopPK) model for tacrolimus in paediatric liver transplant patients and determine optimal sampling strategies to estimate tacrolimus exposure accurately.

Methods

Twelve hour intensive pharmacokinetic profiles from 30 patients (age 0.4–18.4 years) receiving tacrolimus orally were analysed. The PopPK model explored the following covariates: weight, age, sex, type of transplant, age of liver donor, liver function tests, albumin, haematocrit, drug interactions, drug formulation and time post-transplantation. Optimal sampling strategies were developed and validated with jackknife.

Results

A two-compartment model with first-order absorption and elimination and lag time described the data. Weight was included on all pharmacokinetic parameters. Typical apparent clearance and central volume of distribution were 12.1 l h⁻¹ and 31.3 l, respectively. The PopPK approach led to the development of optimal sampling strategies, which allowed estimation of tacrolimus pharmacokinetics and area under the concentration–time curve (AUC) on the basis of practical sampling schedules (three or four sampling times within 4 h) with clinically acceptable prediction error limit. The mean bias and precision of the Bayesian vs. reference (trapezoidal) AUCs ranged from −2.8 to −1.9% and from 7.4 to 12.5%, respectively.

Conclusions

The PopPK of tacrolimus and empirical Bayesian estimates represent an accurate and convenient method to predict tacrolimus AUC_(0–12) in paediatric liver transplant recipients, despite high between-subject variability in pharmacokinetics and patient demographics. The developed optimal sampling strategies will allow the undertaking of prospective trials to define the tacrolimus AUC-based therapeutic window and dosing guidelines in this population.     

Effect of a proton pump inhibitor on the pharmacokinetics of imatinib

AIMS

Imatinib mesylate (Gleevec®/Glivec®), which has revolutionized the treatment of chronic myeloid leukemias (CML) and gastrointestinal stromal tumours (GIST), has been reported to cause gastric upset. Consequently, proton pump inhibitors (PPI) are frequently co-administered with imatinib. Because PPI can elevate gastric pH and delay gastric emptying or antagonize ATP-binding-cassette transporters, they could influence imatinib absorption and pharmacokinetics. We aimed to evaluate whether use of omeprazole has a significant effect on imatinib pharmacokinetics.

METHODS

Twelve healthy subjects were enrolled in a two-period, open-label, single-institution, randomized cross-over, fixed-schedule study. In one period, each subject received 400 mg imatinib orally. In the other period, 40 mg omeprazole (Prilosec®) was administered orally for 5 days, and on day 5 it was administered 15 min before 400 mg imatinib. Plasma concentrations of imatinib and its active N-desmethyl metabolite {"type":"entrez-protein","attrs":{"text":"CGP74588","term_id":"875877231"}}CGP74588 were assayed by LC-MS, and data were analyzed non-compartmentally.

RESULTS

PPI administration did not significantly affect the imatinib area under the plasma concentration vs time curve (AUC) (34.1 µg ml⁻¹ h alone vs 33.1 µg ml⁻¹ h with omeprazole, P= 0.64; 80% power), maximum plasma concentration (C_max) (2.04 µg ml⁻¹ alone vs 2.02 µg ml⁻¹ with omeprazole, P= 0.97), or half-life (13.4 h alone vs 14.1 h with omeprazole, P= 0.13).

CONCLUSIONS

Our results indicate that the use of omeprazole does not significantly affect the pharmacokinetics of imatinib, as opposed to, for example, dasatinib where PPI decreased AUC and C_max two-fold.     

Novel Δ(9) -tetrahydrocannabinol formulation Namisol® has beneficial pharmacokinetics and promising pharmacodynamic effects

AIMS

Among the main disadvantages of currently available Δ⁹-tetrahydrocannabinol (THC) formulations are dosing difficulties due to poor pharmacokinetic characteristics. Namisol® is a novel THC formulation, designed to improve THC absorption. The study objectives were to investigate the optimal administration route, pharmacokinetics (PK), pharmacodynamics (PD) and tolerability of Namisol®.

METHODS

This first in human study consisted of two parts. Panel I included healthy males and females (n = 6/6) in a double-blind, double-dummy, randomized, crossover study with sublingual (crushed tablet) and oral administration of Namisol® (5 mg THC). Based on these results, male and female (n = 4/5) participants from panel I received oral THC 6.5 and 8.0 mg or matching placebo in a randomized, crossover, rising dose study during panel II. PD measurements were body sway; visual analogue scales (VAS) mood, psychedelic and heart rate. THC and 11-OH-THC population PK analysis was performed.

RESULTS

Sublingual administration showed a flat concentration profile compared with oral administration. Oral THC apparent t_1/2 was 72–80 min, t_max was 39–56 min and C_max 2.92–4.69 ng ml⁻¹. THC affected body sway (60.8%, 95% CI 29.5, 99.8), external perception (0.078 log mm, 95% CI 0.019, 0.137), alertness (−2.7 mm, 95% CI −4.5, −0.9) feeling high (0.256 log mm, 95% CI 0.093, 0.418) and heart rate (5.6 beats min^–1, 95% CI 2.7, 6.5). Namisol® was well tolerated.

CONCLUSIONS

Oral Namisol® showed promising PK and PD characteristics. Variability and t_max of THC plasma concentrations were smaller for Namisol® than reported for studies using oral dronabinol and nabilone. This study was performed in a limited number of healthy volunteers. Therefore, future research on Namisol® should study clinical effects in patient populations.     

Predicted metabolic drug clearance with increasing adult age

Aim

To determine the effect of increasing adult age on predicted metabolic drug clearance.

Method

Predicted metabolic drug clearances (CL_PT) were determined using in vitro-in vivo extrapolation coupled with physiological-based pharmacokinetic modelling and simulation (IVIVE-PBPK) in Simcyp®. Simulations were conducted using CYP-selective ‘probe’ drugs with subjects in 5 year age groups (20–25 to 90–95 years). CL_PT values were compared with human pharmacokinetic data stratified according to age (young = 20–40 years and elderly = 65–85 years) and gender. Age-related changes in the physiological parameters used for IVIVE of CL_PT were described.

Results

Predicted metabolic drug clearances decreased with increasing adult age to approximately 65–70 years: caffeine from 1.5 to 1.0 ml min⁻¹ kg⁻¹ (a 33% decrease), S-warfarin from 0.100 to 0.064 ml min⁻¹ kg⁻¹ (36%), S-mephenytoin from 4.1 to 2.5 ml min⁻¹ kg⁻¹ (39%), desipramine from 10.6 to 7.3 ml min⁻¹ kg⁻¹ (31%) and midazolam from 5.4 to 3.9 ml min⁻¹ kg⁻¹ (27%). Except for S-mephenytoin, predictions were within 3.5-fold of clearances from clinical studies when stratified by age and gender. A trend towards higher CL_PT was observed in females, but this was only statistically significant in larger virtual trials. Physiological parameters that determine CL_PT decreased with increasing adult age: mean microsomal protein g^–1 of liver, liver weight, hepatic blood flow and human serum albumin concentration.

Conclusion

Decreased metabolic clearance in the elderly was predicted by Simcyp® and was generally consistent with limited clinical data for four out of five drugs studied and the broader literature for drugs metabolized by CYP enzymes. IVIVE-PBPK may be increasingly useful in predicting metabolic drug clearance in the elderly.     

Octreotide s.c. depot provides sustained octreotide bioavailability and similar IGF-1 suppression to octreotide LAR in healthy volunteers

Aims

The aim was to assess the pharmacokinetics, pharmacodynamics, safety and tolerability of octreotide subcutaneous (s.c.) depot, a novel octreotide formulation.

Methods

This was a phase I, randomized, open label study. After a single dose of octreotide immediate release (IR) 200 µg, subjects were randomized to one of eight groups to receive three monthly injections of octreotide s.c. depot A 10, 20 or 30 mg, B 30 mg, C 10, 20 or 30 mg or long acting octreotide (octreotide LAR) 30 mg.

Results

One hundred and twenty-two subjects were randomized. For all depot variants, onset of octreotide release was rapid and sustained for up to 4 weeks. The relative octreotide bioavailability of depot variants vs. octreotide IR ranged from 0.68 (90% confidence interval [CI] 0.61, 0.76) to 0.91 (90% CI 0.81, 1.02) and, vs. octreotide LAR, was approximately four- to five-fold greater: 3.97 (90% CI 3.35, 4.71) to 5.27 ng ml^–1 h (90% CI 4.43, 6.27). All depot variants showed relatively rapid initial reductions of insulin-like growth factor 1 (IGF-1) compared with octreotide LAR. A trend of octreotide dose dependence was also indicated from the plasma concentrations and suppression of IGF-1. Maximum inhibition of IGF-1 at steady-state was highest for depot B and C. All depot treatments were well tolerated. The most frequent adverse events were gastrointestinal related.

Conclusions

Octreotide s.c. depot provides greater octreotide bioavailability with a more rapid onset and stronger suppression of IGF-1 than octreotide LAR in healthy volunteers.     

Evaluation of limited sampling methods for estimation of tacrolimus exposure in adult kidney transplant recipients

AIMS

To examine the predictive performance of limited sampling methods for estimation of tacrolimus exposure in adult kidney transplant recipients.

METHODS

Twenty full tacrolimus area under the concentration–time curve from 0 to 12 h post-dose (AUC_0–12) profiles (AUCf) were collected from 20 subjects. Predicted tacrolimus AUC_0–12 (AUCp) was calculated using the following: (i) 42 multiple regression-derived limited sampling strategies (LSSs); (ii) five population pharmacokinetic (PK) models in the Bayesian forecasting program TCIWorks; and (iii) a Web-based consultancy service. Correlations (r²) between C₀ and AUCf and between AUCp and AUCf were examined. Median percentage prediction error (MPPE) and median absolute percentage prediction error (MAPE) were calculated.

RESULTS

Correlation between C₀ and AUCf was 0.53. Using the 42 LSS equations, correlation between AUCp and AUCf ranged from 0.54 to 0.99. The MPPE and MAPE were <15% for 29 of 42 equations (62%), including five of eight equations based on sampling taken ≤2 h post-dose. Using the PK models in TCIWorks, AUCp derived from only C₀ values showed poor correlation with AUCf (r² = 0.27–0.54) and unacceptable imprecision (MAPE 17.5–31.6%). In most cases, correlation, bias and imprecision estimates progressively improved with inclusion of a greater number of concentration time points. When concentration measurements at 0, 1, 2 and 4 h post-dose were applied, correlation between AUCp and AUCf ranged from 0.75 to 0.93, and MPPE and MAPE were <15% for all models examined. Using the Web-based consultancy service, correlation between AUCp and AUCf was 0.74, and MPPE and MAPE were 6.6 and 9.6%, respectively.

CONCLUSIONS

Limited sampling methods better predict tacrolimus exposure compared with C₀ measurement. Several LSSs based on sampling taken 2 h or less post-dose predicted exposure with acceptable bias and imprecision. Generally, Bayesian forecasting methods required inclusion of a concentration measurement from <2 h post-dose to adequately predict exposure.     

Pharmacokinetics of two formulations of omeprazole administered through a gastrostomy tube in patients with severe neurodevelopmental problems

AIMS

Omeprazole is often administered through a gastrostomy tube as either (i) a Multiple Unit Pellet System (MUPS®) tablet disintegrated in water (MUPS® formulation), or (ii) a suspension in 8.4% sodium bicarbonate (suspension formulation). This bioavailability study evaluates this practice in tube-fed patients with severe neurodevelopmental problems.

METHODS

Nonblinded, two-phase cross-over trial.

RESULTS

In seven of 10 patients, bioavailability was higher for the suspension formulation than for the MUPS® formulation. Median (90% confidence interval) area under the plasma concentration–time curve ratio (MUPS® over suspension) was 0.5 (0.06–2.37).

CONCLUSIONS

In this population, omeprazole MUPS® formulation has no apparent advantage over the more easily administered suspension formulation.