Laser Doppler imager (LDI) scanner and intradermal injection for in vivo pharmacology in human skin microcirculation: responses to acetylcholine, endothelin-1 and their repeatability

AIMS: The purpose of this study was to evaluate the repeatability of forearm skin blood flow responses to intradermal injections of acetylcholine (ACh) and endothelin-1 (ET-1) using a double injection technique (DIT) and a laser Doppler imager (LDI) scanner in the human skin microcirculation. METHODS: We used a laser Doppler imager (Moor LDI V3.01) to continuously monitor the change in skin blood flow during intradermal administration of physiological saline (0.9% NaCl), acetylcholine (ACh 10(-7), 10(-8), 10(-9) M) and endothelin-1 (ET-1 10(-14), 10(-16), 10(-18) M) in 10 healthy male subjects. Subjects were examined on 3 different days for assessment of interday and interobserver repeatability. Injections of either drug were randomly placed on different sites of the forearm. Laser Doppler images were collected before and after injection at 2.5 min intervals for 30 min. Data were analysed after the completion of each experiment using Moor Software V.3.01. Results are expressed as changes from baseline in arbitrary perfusion units (PU). RESULTS: ACh caused a significant vasodilation (P < 0.0001 anova, mean +/- SE: 766 +/- 152 PU, ACh 10(-9) M; 1868 +/- 360 PU, ACh 10(-8) M; 4188 +/- 848 PU, ACh 10(-7) M; mean of days 1 and 2, n = 10), and ET-1 induced a significant vasoconstrictive response (P < 0.0001 anova, -421 +/- 83 PU, ET-1 10(-18) M; -553 +/- 66 PU, ET-1 10(-16) M; -936 +/- 90 PU, ET-1 10(-14) M; mean of days 1 and 2, n = 10). There was no difference on the response to either drug on repeated days. Bland-Altman analyses showed a close agreement of responses between days with repeatability coefficients of 1625.4 PU for ACh, and 386.0 PU for ET-1 (95% CI: ACh, -1438 to 1747 PU, ET-1, -399 to 358 PU) and between observers with repeatability coefficients of 1057.2 PU for ACh and 255.8 PU for ET-1 (95% CI: ACh, -1024 to 1048 PU, ET-1, -252 to 249 PU). The variability between these responses was independent of average flux values for both ACh and ET-1. There was a significant correlation between responses measured in the same site, in the same individual on two different days by the same observer (ACh, r = 0.94, P < 0.0001; ET-1, r = 0.90, P < 0.0006), and between responses measured by two different observers (ACh, r = 0.94, P < 0.0001; ET-1, r = 0.91, P < 0.0003). CONCLUSION: We have shown that interday and intraobserver responses to intradermal injections of ET-1 and ACh, assessed using the DIT in combination with an LDI scanner, exhibited good reproducibility and may be a useful tool for studying the skin microcirculation in vivo.     

A placebo-controlled study examining the effect of allopurinol on heart rate variability and dysrhythmia counts in chronic heart failure

AIMS: Allopurinol improves endothelial function in chronic heart failure by reducing oxidative stress. We wished to explore if such an effect would attenuate autonomic dysfunction in CHF in line with many other effective therapies in CHF. METHODS: We performed a prospective, randomized, double-blind cross-over study in 16 patients with NYHA Class II-IV chronic heart failure (mean age 67 +/- 10 years, 13 male, comparing allopurinol (2 months) at a daily dose of 300 mg (if creatinine < 150 micromol l-1) or 100 mg (if creatinine > 150 micromol l-1) with matched placebo. Mean heart rate and dysrhythmia counts were recorded from 24 h Holter tapes at monthly intervals for 6 months. We assessed autonomic function using standard time domain heart rate variability parameters (HRV): SDNN, SDANN, SDNN index, rMSSD and TI. RESULTS: Allopurinol had no significant effect on heart rate variability compared with placebo; the results are expressed as a difference in means +/- s.d. with 95% confidence interval (CI) between allopurinol and placebo: SDNN mean = 6.5 +/- 4.8 ms, P = 0.18 and 95% CI (-3.7, 17); TI mean = -2.1 +/- 1.4, P = 0.16 and 95% CI (-5.2, 0.8); SDANN mean = -2.8 +/- 7 ms, P = 0.68 and 95% CI (-18, 12); SDNNi mean = 2 +/- 6.6, P = 0.7 and 95% CI (-12, 16); RMSSD mean = -0.9 +/- 2, P = 0.68 and 95% CI (-5.6, 3.7). For mean heart rate the corresponding results were 0.9 +/- 1.4, P = 0.5 and 95% CI (-2, 3.8). Log 24 h ventricular ectopic counts (VEC) were 0.032 +/- 0.37, P = 0.7 and 95% CI (-0.1, 0.2). Patient compliance with study medication was good since allopurinol showed its expected effect of reducing plasma uric acid (P < 0.001). CONCLUSIONS: Allopurinol at doses, which are known to reduce oxidative stress appear to have no significant effect on resting autonomic tone, as indicated by time domain heart rate variability or on dysrhythmia count in stable heart failure patients.     

Stereoselective pharmacokinetics of cisapride in healthy volunteers and the effect of repeated administration of grapefruit juice

AIMS: To determine whether the pharmacokinetics of cisapride and its interaction with grapefruit juice are stereoselective. METHODS: The study was a randomized, two-phase cross over design with a washout period of 2 weeks. Ten healthy volunteers were pretreated with either water or 200 ml double strength grapefruit juice three times a day for 2 days. On the 3rd each subject ingested a single 10 mg dose of rac-cisapride tablet. Double strength grapefruit juice (200 ml) or water was administered during cisapride dosing and 0.5 and 1.5 h thereafter. Blood samples were collected before and for 32 h after cisapride administration. Plasma concentrations of cisapride enantiomers were measured by a chiral h.p.l.c. method. A standard 12-lead ECG was recorded before cisapride administration (baseline) and 2, 5, 8, and 12 h later. RESULTS: This study showed that cisapride pharmacokinetics are stereoselective. In control (water treated) subjects, the mean Cmax (30 +/- 13.6 ng ml-1; P = 0.0008) and AUC(0, infinity) (201 +/- 161 ng ml-1 h; P = 0.029) of (-)-cisapride were significantly higher than the Cmax (10.5 +/- 3.4 ng ml-1) and AUC(0, infinity) (70 +/- 51.5 ng ml-1 h) of (+)-cisapride. There was no marked difference in elimination half-life between (-)-cisapride (4.7 +/- 2.7 h) and (+)-cisapride (4.8 +/- 3 h). Compared with the water treated group, grapefruit juice significantly increased the mean Cmax of (-)-cisapride from 30 +/- 13.6-55.5 +/- 18 ng ml-1 (95% CI on mean difference, -33, -17; P = 0.00005) and of (+)-cisapride from 10.5 +/- 3.4 to 18.4 +/- 6.2 ng ml-1 (95% CI on mean difference, -11.8, -3.9, P = 0.00015). The mean AUC(0, infinity) of (-)-cisapride was increased from 201 +/- 161 to 521.6 +/- 303 ng ml-1 h (95% CI on mean difference, -439, -202; P = 0.0002) and that of (+)-cisapride from 70 +/- 51.5 to 170 +/- 91 ng ml-1 h (95% CI on mean difference, -143, -53; P = 0.0005). The tmax was also significantly increased for both enantiomers (from 1.35 to 2.8 h for (-)-cisapride and from 1.75 to 2.9 h for (+)-cisapride in the control and grapefruit juice group, respectively; P < 0.05). The t(1/2) of (-)-cisapride was significantly increased by grapefruit juice, while this change did not reach significant level for (+)-cisapride. The proportion of pharmacokinetic changes brought about by grapefruit juice was similar for both enantiomers, suggesting non-stereoselective interaction. We found no significant difference in mean QTc intervals between the water and grapefruit juice treated groups. CONCLUSIONS: The pharmacokinetics of cisapride is stereoselective. Grapefruit juice elevates plasma concentrations of both (-)- and (+)-cisapride, probably through inhibition of CYP3A in the intestine. At present, there are no data on whether the enantiomers exhibit stereoselective pharmacodynamic actions. If they do, determination of plasma concentrations of the individual enantiomers as opposed to those of racemic cisapride may better predict the degree of drug interaction, cardiac safety and prokinetic efficacy of cisapride.     

Variability in the stereoselective disposition of ibuprofen in patients with rheumatoid arthritis.

1. Patients suffering from rheumatoid arthritis received oral doses of 600 mg racemic ibuprofen (n = 25; RAC) or 400 mg (S)-ibuprofen (n = 25; S-IBU) in a double-blind, randomized parallel-group study. 2. The pharmacokinetic parameters of (S)-ibuprofen were not statistically different between treatments (P > 0.05). Comparing (S)- and (R)-ibuprofen within the group receiving the racemate significantly higher Cmax (20.3 +/- 5.3 vs 17.7 +/- 4.4 micrograms ml-1; P < 0.02; 95% confidence interval for differences (CI): 0.5-4.6), AUC (86.2 +/- 23.5 vs 67.6 +/- 26.6 micrograms ml-1 h; P < 0.001; CI: 9.5-27.6), mean residence time (4.5 +/- 1.1 vs 4.1 +/- 1.2 h; P < 0.01; CI: 0.1-0.6) and renal clearance (0.8 +/- 0.6 vs 0.0 +/- 0.0 ml min-1; P < 0.001; CI: 0.5-1.0) values were observed for the (S)-enantiomer. 3. No difference was found (P > 0.05) between treatments in the percentage of the dose recovered in the urine as (R)- or (S)-ibuprofen plus metabolites (S-IBU: 80.2 +/- 8.47 vs RAC: 74.1 +/- 14.0%). 4. Interindividual variation in the pharmacokinetics of (S)-ibuprofen following administration of the racemate was similar to that following the administration of the single isomer suggesting that chiral inversion is not a major factor contributing to variability in the disposition of this drug.     

Contribution of nitric oxide to beta2-adrenoceptor mediated vasodilatation in human forearm arterial vasculature

AIMS: beta2-adrenoceptor agonists are generally considered to produce endothelium independent vasodilatation through adenylate cyclase. We determined whether nitric oxide contributes to beta2-adrenoceptor vasodilatation in human arterial vasculature. METHODS: Forearm blood flow responses to brachial intra-arterial infusions of ritodrine (2.5-50 microg min(-1)), a selective beta2-adrenoceptor agonist, were determined in 24 healthy, normotensive subjects (mean age 22 years, 5F) on two occasions with initial and concomitant administration of L-NMMA (800 microg min(-1)), an NO synthase inhibitor, or noradrenaline (5-30 ng min(-1)), a control constrictor not affecting basal NO activity. Responses to the endothelium dependent vasodilator scrotonin (n = 6) and an endothelium independent vasodilator GTN (n = 9) were also determined. RESULTS: Maximal dilatation to ritodrine during L-NMMA infusion (310+/-32%; mean+/-s.e.mean) was reduced compared to that during noradrenaline infusion (417+/-41%, P<0.05), as were summary responses (1023+/-101 vs 1415+/-130; P<0.05). Responses to GTN were unaffected by L-NMMA compared to noradrenaline; max 177+/-26 vs 169+/-20%, 95% CI for difference -33,48; P=0.68; summary response 361+/-51 vs 396+/-37, 95% CI -142,71; P=0.46. Dilator responses to serotonin were reduced by L-NMMA; max 64+/-20 vs 163+/-26%, P<0.01; summary response 129+/-36 vs 293+/-60; P<0.05) and to a greater extent than ritodrine (58+/-7 vs 25+/-14%, P<0.05). CONCLUSIONS: beta2-adrenoceptor mediated vasodilatation in the human forearm has an NO mediated component. The underlying mechanism for this effect is unclear, but flow mediated vasodilatation is unlikely to be responsible.     

Relative bioavailability of a new oral form of cyclosporin A in patients with rheumatoid arthritis.

The relative bioavailability of cyclosporin A (CsA) from a new microemulsion oral formulation (NEO) and the currently used soft gelatine capsule (SGC) was determined at steady state in 12 patients with rheumatoid arthritis. The AUC(0,12 h) values of cyclosporin A were significantly greater after NEO than SGC (2873 +/- 848 ng ml-1 h (mean +/- s.d.) vs 2355 +/- 1128 ng ml-1 h; P = 0.02, 95% CI (confidence interval of the difference: 81 to 955 ng ml-1 h). Cmax values were significantly higher after NEO than after SGC (811 +/- 244 ng ml-1 vs 495 +/- 291 ng ml-1, P < 0.0001, 95% CI of the difference: 209 to 422 ng ml-1).     

Effects of sex on the pharmacokinetic and pharmacodynamic properties of quinidine

AIMS: To investigate the source of the apparent increased susceptibility of women to develop QT interval prolongation and torsade de pointes after the administration of drugs that delay cardiac repolarization. METHODS: Plasma quinidine concentrations and electrocardiographic changes (QRS and QT intervals) were measured over 24 h following the administration of single oral doses of the QT prolonging drug quinidine (3 mg kg(-1)) and compared between 27 male and 21 female healthy volunteers. RESULTS: There were no significant differences between males and females in plasma quinidine concentrations or in calculated pharmacokinetic variables. Maximum quinidine concentrations in males and females were 997 +/- 56 and 871 +/- 57 ng ml(-1), respectively (mean difference (-125, 95% confidence intervals (CI) -239, 11 ng ml(-1), P = NS). Quinidine lengthened actual (QTa) and corrected (QTc) QT intervals and the QRS interval to a greater extent in females than males (P < 0.001 for each), but there were no significant sex differences detected in the effects of quinidine on the heart rate corrected JT interval. Maximum prolongation of QTc interval was observed 2 h after quinidine and was significantly greater in women (33 +/- 16 vs 24 +/- 17 ms, mean difference 9 +/- 20 ms, 95% CI 3, 15, P = 0.037). At this time mean differences (95% CI) were 1.0 min(-1) (-2.5, 4.4, P = NS) for heart rate, 5.5 ms (3.5, 7.6, P = 0.05) for the QRS and 3.4 ms (-2.5, 9.3, P = NS) for the JTc intervals. CONCLUSIONS: Quinidine-induced increases in QTc were larger in females, but no sex differences in quinidine pharmacokinetics were found. The disparity in prolongation of cardiac repolarization is thus due to a pharmacodynamic difference which appears more complex than simply an increase in repolarization delay in females.     

Safety and efficacy of tramadol in the treatment of idiopathic detrusor overactivity: a double-blind, placebo-controlled, randomized study

AIM: To evaluate the efficacy and safety of tramadol in patients with idiopathic detrusor overactivity (IDO). METHODS: A total of 76 patients 18 years or older with IDO were randomly assigned to receive 100 mg tramadol sustained release (group 1, n = 38) or placebo (group 2, n = 38) every 12 h for 12 weeks. Clinical evaluation was performed at baseline and every 2 weeks during treatment. All patients underwent urodynamics and ice water test at baseline and 12-week treatment. Main outcome measures were number of voids per 24 h, urine volume per void and episodes of urge incontinence per 24 h on a frequency volume chart and detailed recording of adverse effect. RESULTS: After 12 weeks of treatment mean number of voids per 24 h +/- SD decreased from 9.3 +/- 3.2 to 5.1 +/- 2.1 (P < 0.001 vs. placebo) [95% confidence interval (CI) -5.1--0.4]. At that time mean urine volume per void increased from 158 +/- 32 to 198 +/- 76 ml (P < 0.001 vs. placebo) (95% CI 8-22), while mean number of incontinence episodes per 24 h decreased from 3.2 +/- 3.3 to 1.6 +/- 2.8 (P < 0.001 vs. placebo) (95% CI -2-0.3). Tramadol induced significant improvements in urodynamic parameters. More adverse effects were associated with tramadol treatment than with placebo (P < 0.05). The main adverse event with tramadol was nausea. CONCLUSIONS: In patients with non-neurogenic IDO tramadol provided beneficial clinical and urodynamic results. Further studies are required to draw final conclusions on the efficacy of this drug in IDO.     

Effects of intradermal injection of atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) causes mast cell degranulation in rats in vivo and in vitro but is bronchodilator in humans. The aim of this study was to investigate the wheal and flare dose-response to intradermal injection of alpha-human ANP in normal humans. Eight normal subjects received five 30 microliters injections containing 1, 10, 39, 78, 117 pmol ANP and one each of normal saline, histamine 675 pmol and substance P 30 pmol. Maximum ANP flare response was greater but not significantly than that to saline at 1.55 +/- 0.6 (mean +/- s.e. mean) compared with 0.42 +/- 0.17 cm2, but much less than to histamine 9.86 +/- 0.97 or to substance P 12.5 +/- 1.2. Maximum ANP wheal response was significantly greater than that to saline at 0.38 +/- 0.08 compared with 0.18 +/- 0.05 cm2 (difference between means 0.20, 95% CI 0.05, 0.35), but much less than to histamine 0.75 +/- 0.06 or to substance P 1.05 +/- 0.08 cm2. No dose-response to ANP was demonstrated, though responses to the highest dose differed significantly from those to the lowest dose studied. We conclude that human cutaneous responses to ANP differ from those of animals and that the skin is less responsive than other tissues in humans.     

C-peptide has no effect on forearm blood flow during local hyperinsulinaemia in healthy humans

BACKGROUND: C-peptide increases forearm blood flow (FBF) in patients with Type 1 diabetes, probably by interaction with insulin, but not in healthy subjects. It is unclear if the vasodilating effect is sealed at normal fasting insulin concentrations. METHODS: The effects of C-peptide alone and during local hyperinsulinaemia were studied in healthy young men. Subjects received intra-arterial insulin at 6 pmol min-1 (low dose) or placebo for 60 min with subsequent coinfusion of C-peptide at increasing doses of 2-60 pmol min-1 in a double-blind crossover study (n = 8). In control experiments insulin at 30 pmol min-1 (high dose) was coinfused with C-peptide (n = 3). FBF was measured by strain-gauge plethysmography. RESULTS: Placebo had no effect on FBF (mean percentage change from baseline at 50 min -3.1%, 95% confidence interval [CI]-14.9, + 8.7). Insulin infusion slightly enhanced FBF by + 10.2% (95% CI -6.8, + 27.2; low dose) and + 17.6% (95% CI -38.8, + 74.0; high dose), respectively. The mean individual difference of the change in FBF between low-dose insulin and placebo was + 13.3% (95% CI -6.0, + 32.7; P = NS). Infusion of C-peptide increased local C-peptide concentrations from 1.8 +/- 0.1 ng ml-1 to 6.1 +/- 2.8 ng ml-1, but had no effect on FBF during placebo or hyperinsulinaemia (mean difference vs low dose insulin -16.0%, 95% CI -38.9, + 6.9). CONCLUSION: The vasodilating effect of C-peptide seen in Type 1 diabetes is not detectable during fasting or hyperinsulinaemia in the forearm vasculature of healthy subjects. This suggests saturation of its vasodilating potency at insulin concentrations within the normal or in the supraphysiological range.     

Cigarette smoking in men and vascular responsiveness

AIMS: Smoking is a major risk factor for developing atherosclerosis. In order to understand the vascular abnormalities observed in smokers, we investigated vascular responsiveness in cigarette smokers. METHODS: We performed two consecutive matched group comparative studies to investigate vascular responsiveness using venous occlusion plethysmography. The mean effects of three incremental doses of each vasoactive agent are presented. Both studies compared smokers with nonsmokers. RESULTS: The first investigated 68 subjects (smokers = 29; mean +/- s.d. ages; 24 +/- 6 vs 25 +/- 5 years; P = NS) and found smoking was associated with a significant blunting of the flow ratio between treated and untreated arms to endothelium-dependent vasodilatation to acetylcholine (mean +/- s.d., nonsmokers vs smokers) 4.07 +/- 2.18 vs 3.42 +/- 1.79 (P = 0.04, 95% CI 0.02, 1.12). By contrast, there was no significant difference in the responses to the endothelium-independent vasodilators sodium nitroprusside and verapamil. Smoking was also associated with a significant impairment in endothelium-dependent vasoconstriction induced by monomethyl-L-arginine (L-NMMA) 0.78 +/- 0.22 vs 0.87 +/- 0.21 (P = 0.006, 95% CI -0.14, -0.02) and a trend to blunted endothelium-independent vasoconstrictor responses to noradrenaline. In the second study we investigated the response to angiotensin I and II in 23 subjects (smokers = 12; mean +/- s.d. ages; 34 +/- 10 vs 32 +/- 11 years). There was significant impairment in smokers of the mean vasoconstrictor response to angiotensin I 0.51 +/- 0.15 vs 0.59 +/- 0.16 (nonsmokers vs smokers; P = 0.003, 95% CI -0.13, -0.03) and a nonsignificant trend towards impairment of the response to angiotensin II. CONCLUSIONS: Cigarette smoking in male volunteers is associated with blunted basal and stimulated nitric oxide bioactivity. Endothelial independent vasodilator responses (to nitroprusside and verapamil) were unaltered in smokers. A defect in the vasoconstrictor response to angiotensin I was also seen.     

The effects of rifampicin on the pharmacokinetics and pharmacodynamics of orally administered nilvadipine to healthy subjects

AIMS: To study the effects of rifampicin on the pharmacokinetics and pharmacodynamics of nilvadipine. METHODS: Five healthy adult volunteers received nilvadipine (4 mg) orally before and after a 6 day treatment with rifampicin. Blood and urine were collected and assayed for plasma nilvadipine and urinary 6beta-hydroxycortisol and cortisol. RESULTS: The treatment with rifampicin reduced the mean (+/- s.d.) AUC of nilvadipine from 17.4 +/- 8.4 to 0.6 +/- 0.4 microg l-1 h (mean difference -16.8 microg l-1 h, 95% CI -9.4, 24.2 microg l-1 h). While the administration of nilvadipine alone elicited a significant (P < 0.05) hypotensive (mean difference for diastolic blood pressure -8 mmHg, 95% CI -4, -12 mmHg) and reflex tachycardia (mean difference 5 beats min-1, 95% CI 1, 9 beats min-1), the treatment with rifampicin abolished these responses. The urinary 6beta-hydroxycortisol/cortisol ratio showed a significant (P < 0.05) increase from 10.3 +/- 4.0 to 50.3 +/- 24.6 by rifampicin: mean difference 40.1, 95% CI 20.4, 59.8. CONCLUSIONS: Because rifampicin may greatly decrease the oral bioavailability of nilvadipine, caution is needed when these two drugs are to be coadministered.     

Effect of widely used combinations of antiretroviral therapy on liver CYP3A4 activity in HIV-infected patients

AIMS: To evaluate the effects of combined antiretroviral drugs (HAART) on liver CYP3A4 activity using the [(14)C-N-methyl]-erythromycin breath test (ERMBT). METHODS: HIV-infected patients (31 women, 30 men) with mean (+/- SD) age of 38 +/- 9 years were enrolled and underwent complete clinical and laboratory evaluation. Patients were divided into five groups and were treated with two nucleoside analogues (NAs) and one of the following: nelfinavir alone (n = 13), any ritonavir-boosted protease inhibitor with (n = 8) or without (n = 13) nevirapine, nevirapine alone (n = 15), or a third NA (n = 12). Three or four ERMBTs were performed 7 days prior to (D-7) and at the beginning of treatment (D0), D14 (only for patients taking nevirapine) and on D28. RESULTS: Mean baseline liver CYP3A4 activity displayed high interindividual variability (47%) but low intraindividual variability (15%). Women had 30% higher ERMBT values than men [2.7 +/- 1.3 vs. 1.9 +/- 0.7; 95% confidence interval (CI) 20.5, 49.5; P = 0.003]. The ERMBT data correlated with body weight, alpha- and beta-globulins and alanin aminotransferases (0.10 < r(s) < 0.20; P < 0.01). Whereas nevirapine had no effect on liver CYP3A4 activity, nelfinavir-based and ritonavir-boosted drug regimens inhibited it by 69% (95% CI 64.7, 72.9; P = 0.005) and by 95% (95% CI 93.3, 96.7; P = 0.001), respectively. CONCLUSION: Evaluation of the effect of HAART on liver CYP3A4 activity may aid in preventing inappropriate treatment regimens in HIV-infected patients.     

Effect of iron(III) chitosan intake on the reduction of serum phosphorus in rats

Because of the widespread use of aluminium- and calcium-containing phosphate binders for the control of hyperphosphataemia in patients with end-stage renal failure, an iron(III) chitosan complex was synthesised and fed to rats to measure its effect on serum phosphorus and calcium, intestinal phosphate binding and phosphate absorption. Thirty-six Wistar rats were randomly selected and distributed into a baseline group (n = 6), a control group (n = 8 (days 0-15), n = 8 (days 16-30)) and a treatment group (n = 8 (days 0-15), n = 8 (days 16-30)). The control groups ingested AIN-76 diet mix with a 1% w/w fibre content; however, the treatment groups had the fibre content completely substituted with iron(III) chitosan. The mean weights of the treated rats were slightly lower from 15 days (not significant); but overall, rat growth was not stunted in the treatment groups. The serum phosphorus levels of the treated group (n = 8) were significantly reduced after 15 days (P = 0.004; control: 5.7+/-0.9 mg dL(-1); treatment: 4.4+/-0.5 mg dL(-1); 95% CI of difference: 0.5-2.2) and 30 days (P = 0.002; control: 5.5+/-0.9 mg dL(-1); treatment = 4.1+/-06 mg dL(-1); 95% CI of difference: 0.6-2.3) as compared with the respective control group. The serum calcium-phosphorus product was 62.0+/-12.1 mg2 dL(-2) for the control and 45.1+/-6.6 mg2 dL(-2) for the treatment group after 30 days (P = 0.004). The serum iron concentration of the treatment group did not differ from the baseline value after 15 and 30 days, but the treatment group was significantly higher than the control group (P<0.05) after 30 days. The faeces phosphorus levels (mg day(-1)) were higher (P<0.01) and its iron content was much higher (P<0.01) for the treated group. The urine phosphorus (mg kg(-1)) was not significantly reduced for the treated group, but the mean was consistently less. The kidney and liver weights of both groups were similar, but the phosphorus content of the kidney (mg (g kidney)(-1)) was higher for the treated group after 30 days (P = 0.041; control, 4.2+/-1.2 mg g(-1) vs treatment, 5.6+/-1.4 mg g(-1). Because iron(III) chitosan had a high phosphorus-binding capacity of 308 (mg P) per gram of Fe3+ for both the in-vitro (pH 7.5) and in-vivo studies, which is greater than nearly all commonly used phosphate binders, and a small net phosphorus absorption difference of 3.7 mg day(-1), it is an efficient phosphate binder for lowering serum phosphate levels without increasing serum calcium levels.     

A double masked placebo controlled study on the effect of nifedipine on optic nerve blood flow and visual field function in patients with open angle glaucoma

AIMS: To investigate whether nifedipine affects ocular perfusion or visual fields in open angle glaucoma patients. METHODS: In a parallel group study nifedipine or placebo was administered for 3 months (n = 30). Ocular fundus pulsation amplitude (FPA), cup blood flow (Flowcup) and visual field mean deviation (MD) were measured. RESULTS: Five patients receiving nifedipine discontinued due to adverse events. Nifedipine did not affect FPA [difference: 0.3 microm (95% CI -0.3,0.9); P = 0.70], Flowcup: [difference: -9 rel.units (95% CI -133,114); P = 0.99], or MD [difference: 0.2dB (95% CI -2.2,2.7); P = 0.51] vs placebo. CONCLUSIONS: Systemic nifedipine is not well tolerated in glaucoma patients and exerts no effect on visual fields or ocular perfusion.     

Meta-analysis of smooth muscle relaxants in the treatment of irritable bowel syndrome

AIM: To update previous overviews of placebo-controlled double-blind trials assessing the efficacy and tolerance of smooth muscle relaxants in irritable bowel syndrome. METHODS AND TRIALS: A total of 23 randomized clinical trials were selected for meta-analyses of their efficacy and tolerance. Six drugs were analysed: cimetropium bromide (five trials), hyoscine butyl bromide (three trials), mebeverine (five trials), otilium bromide (four trials), pinaverium bromide (two trials) and trimebutine (four trials). The total number of patients included was 1888, of which 945 received an active drug and 943 a placebo. RESULTS: The mean percentage of patients with global improvement was 38% in the placebo group (n=925) and 56% in the myorelaxant group (n=927), in favour of myorelaxants with a mean odds ratio of 2.13, P < 0.001 (95% CI: 1.77--2.58) and a mean risk difference of 22% P < 0.001 (95% CI: 13--32%). The percentage of patients with pain improvement was 41% in the placebo group (n=568) and 53% in the myorelaxant group (n=567): odds ratio 1.65, P < 0.001 (95% CI: 1.30--2.10) and risk difference 18%, P < 0.001 (95% CI: 7--28%). There was no significant difference for adverse events. CONCLUSION: Myorelaxants are superior to placebo in the management of irritable bowel syndrome.     

THE EFFECT OF INHALED FENOTEROL AND IPRATROPIUM BROMIDE ON PROPRANOLOL INDUCED BRONCHOCONSTRICTION IN THE ASTHMATIC AIRWAYS

1. The provocative dose of inhaled propranolol, (PC20P, mg/mL) needed to induce a 20% reduction in the forced expired volume in 1 s (FEV1, L) was determined for 15 adult asthmatics following randomized pre-treatment with placebo, ipratropium bromide (40, 160 micrograms) and fenoterol (200, 800 micrograms) aerosols using a double-blind protocol. 2. Fenoterol 200 micrograms, 800 micrograms increased the baseline FEV1 0.28 +/- 0.16, 0.32 +/- 0.16 L (P = 0.04, P = 0.008 respectively). Fenoterol 800 micrograms moved the PC20 P rightwards from placebo geometric mean 10.95, 95% Confidence Intervals (95% CI) 4.43-27.22 mg/mL to mean 20.41, 95% CI 10.13 to 40.64 mg/mL (P = 0.01). Fenoterol 200 micrograms was not protective; mean PC20 16.22, 95% CI 7.83-34.35 mg/mL (P = 0.08). Neither 40 or 160 micrograms ipratropium changed the FEV1 or PC20P values compared with placebo; increase in FEV1 0.15 +/- 0.27 L (P = 0.22), 0.24 +/- 0.12 L (P = 0.14) and geometric mean PC20P 16.59 +/- 0.57 mg/mL, 95% CI 8.01-34.51 mg/mL (P = 0.90), 15.58 +/- 0.66 mg/mL, 95% CI 6.72-36.05 mg/mL (P = 0.34) respectively after ipratropium treatments. 3. Bronchoconstriction induced by inhaled propranolol (P) appears to be only weakly antagonized by inhaled beta-agonist and not reduced by antimuscarinic anticholinergic aerosol. This finding argues against the activation of a cholinergic reflex to explain propranolol induced bronchoconstriction (PIB).     

The effect of tocainide on theophylline metabolism.

The effect of 5 days of oral tocainide (400 mg every 8 h) on the kinetics of theophylline given as a single 5 mg kg-1 i.v. infusion over 30 min was investigated in eight healthy male nonsmokers. Treatment with tocainide decreased the plasma clearance of theophylline from 37.5 +/- 6.9 (mean +/- s.d.) to 33.7 +/- 5.0 ml kg-1 h-1 (difference -3.8, 95% CI, -1.7 to -5.9; P = 0.004) and increased its terminal elimination half-life from 9.7 +/- 2.5 to 10.4 +/- 2.1 h (difference 0.7, 95% CI, 0.2 to 1.2; P = 0.011). Tocainide decreased the formation clearances of 3-methylxanthine and 1-methyluric acid, but the formation clearance of 1,3-dimethyluric acid was unaltered. These data indicate that tocainide exerts a modest inhibitory effect on theophylline metabolism. The magnitude of this change is substantially smaller than that reported to be produced by mexiletine.     

An oral yohimbine/L-arginine combination (NMI 861) for the treatment of male erectile dysfunction: a pharmacokinetic, pharmacodynamic and interaction study with intravenous nitroglycerine in healthy male subjects

AIMS: Interaction of phosphodiesterase type 5 inhibitors for the treatment of erectile dysfunction with organic nitrates could lead to severe hypotension. NMI 861 is a combination of 7.7 mg yohimbine tartrate and 6 g l-arginine glutamate. A similar oral combination, which contains the same amount of yohimbine and L-arginine, has been shown to improve erectile function in previous studies. METHODS: In two placebo-controlled, randomized, double-blind, two-way crossover design studies we aimed to assess first the pharmacokinetics and pharmacodynamics of a single oral dose of NMI 861 administered in 16 healthy male subjects, and then the pharmacodynamics of orally administered NMI 861 in combination with intravenous nitroglycerine (GTN) in 12 healthy male subjects. Systolic (SBP) and diastolic (DBP) blood pressures, pulse rate and adverse events were measured in each study. RESULTS: NMI 861 was well tolerated by all subjects with no significant adverse reactions reported. For L-arginine, mean C(max) +/- SEM (range) was 42 +/- 2.2 (28-63) microg ml(-1) and t(max) (range) was 0.88 (0.50-1.5) h. AUC and t(1/2) were not calculated for L-arginine because of the presence of endogenous concentrations and the contribution from food sources. For yohimbine, mean C(max) was 42 +/- 11 (2.8-128) ng ml(-1); t(max) was 0.57 (0.25-1.0) h; mean AUC(0,8 h) was 65 +/- 24 (5.4-332), ng ml(-1) h and t(1/2) was 1.0 +/- 0.34 (0.40-6.0) h. There was a small but significant difference in the mean change from baseline for SBP from 0 to 6 h after NMI 861 treatment compared with placebo (0.8 +/- 1.4 vs-4.1 +/- 2.1 mmHg, respectively; 95% CI 0.0, 9.8 mmHg (P = 0.047)). There was no significant difference in SBP between treatments for the studied periods 6-12 h and 12-24 h. There was no significant difference in DBP or pulse between NMI 861 and placebo treatments for the three studied time periods. In the study designed to investigate the interaction of organic nitrate with NMI 861, subjects were infused intravenously with increasing doses of GTN (15 min each dose) at 2.5, 5, 10, 20 and 40 microg min(-1) starting 40 min after a single oral dose of either NMI 861 or placebo. There was no significant difference in the hypotensive response induced by GTN between the NMI 861 and placebo treatments. The mean maximum changes from baseline during GTN infusion for subjects administered with either NMI 861 or placebo were a decrease of 16.9 +/- 3.4 vs 13.6 +/- 2.4 mmHg (mean difference between treatments -3.3 mmHg, 95% CI -12.7, 6.0 mmHg (P = 0.460)) for SBP, a decrease of 14.7 +/- 2.0 vs 14.0 +/- 2.0 mmHg for DBP (mean difference -0.7 mmHg, 95% CI -8.2, 6.8 mmHg (P = 0.835)), and an increase of 11.8 +/- 1.9 vs 14.1 +/- 2.4 beats min(-1) for pulse, respectively (mean difference -2.3 beats min(-1), 95% CI -9.3, 4.5 beats min(-1) (P = 0.464)). CONCLUSIONS: Acute oral administration of NMI 861 was found to be well tolerated and bioavailable in healthy male subjects and no significant hypotensive interaction with intravenous GTN was detected at the doses investigated.     

Spinal nociception induced by intramuscular injection of oxytetracycline preparations in rats and pigs

Some drug formulations for intramuscular use may cause damage, which potentially can be associated with pain. In animals, spinal nociception can be assessed by stereological quantification of number of regional dorsal horn neurones containing intranuclear Fos-protein as a consequence of expression of the c-fos gene. The aim of the present study was to use c-fos gene expression as a measure of nociceptive input after intramuscular injection of different oxytetracycline formulations. Rats were given a 0.3 ml intramuscular injection in the thigh of one of two 100 mg/ml oxytetracycline preparations (Maxicyklin Vet., Boehringer-Ingelheim or Engemycin Vet., Intervet; n=6 for both), 0.9% saline (n=4) or 4% formalin (n=2). In addition, five pigs were given an intramuscular injection of Aquacykline Vet. (Rosco) in a dose of 1.0 ml/10 kg. After three hours the animals were anaesthetised and perfusion fixed and their spinal cords were taken out. Cryostate sections of the spinal cords were stained immunohistochemically for Fos-protein in dorsal horn neurones and then subjected to stereological quantification of Fos-positive neurones. Rats receiving a saline injection had 905+/-586 (mean+/-S.D.) Fos-positive neurones, whereas formalin injection increased this number to 11,091+/-4,825. Rats receiving an injection of Engemycin had 1,932+/-893 Fos-positive neurones, which was not significantly different from the saline group. In contrast, injection with Maxicyklin increased the number of Fos-positive neurones to 5,488+/-3,116, which was higher than after injection of saline (P<0.05). In pigs receiving an Aquacyklin injection, the number of Fos-positive neurones was 3,493+/-2,027, which was not significantly higher than the previously determined basal level. The increased neuronal activation after intramuscular injection of Maxicyklin Vet. may suggest that injection of this drug may be more painful than injection with saline. In contrast, no significant difference in neuronal activation caused by saline and Engemycin Vet. was found.