A pharmacokinetic interaction study between butorphanol and sumatriptan nasal sprays in healthy subjects: importance of the timing of butorphanol administration.

Sumatriptan and butorphanol nasal sprays are commonly used agents for the management of migraine headaches. Under certain circumstances, these two agents may be administered closely in time. However, the possibility of a pharmacokinetic interaction and the safety of this regime have not been examined. In this crossover design study, 24 healthy subjects received the following four treatments, each separated by at least 7 days: 1 mg butorphanol (Stadol NS7); 20 mg sumatriptan (Imitrex Nasal Spray); or both formulations together with butorphanol administered either 1 or 30 min after sumatriptan. Serial plasma samples were collected for 24 h post-dose and analysed for butorphanol and/or sumatriptan by HPLC-MS/MS. Butorphanol plasma concentrations were reduced when it was administered 1 min (mean 28.6% decrease in AUC(0-infinity)), but not 30 min, after sumatriptan. The pharmacokinetics of sumatriptan were not substantially altered by butorphanol. The combination of nasally administered sumatriptan and butorphanol appeared safe. However, if butorphanol nasal spray is administered <30 min after sumatriptan nasal spray, the analgesic effect of butorphanol may be diminished due to reduced nasal absorption resulting from probable transient vasoconstriction of nasal blood vessels by sumatriptan.

Cirrhosis does not affect the pharmacokinetics and pharmacodynamics of clopidogrel.

Clopidogrel, a new platelet ADP receptor antagonist used for the prevention of vascular ischemic events, is converted to an active metabolite via the cytochrome P450 system. Patients with cirrhosis may not metabolize drugs normally and may, in addition, have a number of defects in the coagulation system. To assess the effect of cirrhosis on the pharmacokinetics and pharmacodynamics of clopidogrel, the authors performed an open-label, parallel-group study of 12 patients with Child-Pugh Class A or B cirrhosis and 12 matched controls. All 24 subjects received clopidogrel 75 mg PO QD for 10 days. Pharmacokinetics of clopidogrel and the major metabolite SR 26334 were analyzed on Days 1 and 10; pharmacodynamics were assessed by the inhibition of ADP-induced platelet aggregation and by bleeding time prolongation factor. Pharmacokinetic analysis of clopidogrel was limited due to low plasma concentrations arising from rapid hydrolysis to SR 26334. The Cmax at SS for clopidogrel was higher in cirrhotics than in normals. However, exposures to the metabolite SR 26334, as measured by AUC(tau), were comparable. At Day 10, there was not a statistically significant difference in mean inhibition of platelet aggregation (49.2% +/- 38.6% in cirrhotics vs. 66.7% +/- 7.5% in normals) or in bleeding time prolongation factor (1.64 +/- 0.49 in cirrhotics vs. 1.54 +/- 0.87 in normals) between groups. No significant adverse events, including bleeding events, were reported. In conclusion, there were no significant differences in the pharmacokinetics and pharmacodynamics of clopidogrel in this group of subjects with cirrhosis and matched normals. Therefore, no dosage adjustment of clopidogrel is required in patients with Child-Pugh Class A or B cirrhosis.

The effect of nefazodone on the single-dose pharmacokinetics of phenytoin in healthy male subjects.

The effect of nefazodone on the pharmacokinetics of a single dose of phenytoin was evaluated in 18 healthy male subjects. The subjects received a single oral dose of phenytoin, 300 mg, on day 1 of the study and the pharmacokinetic profile of the drug was determined. After a washout period followed by oral administration of nefazodone, 200 mg twice daily for 7 days, subjects received a single dose of phenytoin, 300 mg concomitantly with the morning dose of nefazodone on day 12, and the pharmacokinetic profile of phenytoin was determined again. Minimum plasma concentrations of nefazodone and its main metabolites indicated that steady state had been achieved for nefazodone when phenytoin and nefazodone were administered concomitantly. No significant differences were demonstrated between mean single-dose pharmacokinetic parameters of phenytoin when administered alone on day 1 and concomitantly with nefazodone on day 12. Assessment of adverse events, clinical laboratory parameters, electrocardiograms, vital signs, and physical examinations indicated that concomitant administration of nefazodone and phenytoin was safe and well tolerated. These data demonstrate that nefazodone does not affect the single-dose pharmacokinetics of phenytoin, but do not preclude the possibility of such an interaction when phenytoin is administered on a long-term basis. A clinically significant interaction between nefazodone and phenytoin through a pharmacokinetic mechanism is unlikely.

A pharmacokinetic-pharmacodynamic model of d-sotalol Q-Tc prolongation during intravenous administration to healthy subjects.

The objective of this study was to assess the pharmacokinetics and pharmacodynamics of the dextro (d-) isomer of sotalol, a class III antiarrhythmic agent, in healthy young men and women after a single intravenous bolus dose. The design was open-label, randomized, parallel group. Each group (4 men and 4 women) received either 0.5, 1.5, or 3.0 mg/kg d-sotalol as an intravenous infusion for 2 minutes. Serial measurements of the d-sotalol plasma concentration and the Q-Tc interval data were recorded before, during, and for 72 hours after drug administration. The pharmacokinetics of d-sotalol were found to be well described by a three-compartment model with linear elimination clearance from the central compartment. There were no significant differences in the elimination clearance or volume of the central compartment between dose levels or between men and women. However, women were found to have a lower steady-state volume of distribution than men (1.20 L/Kg versus 1.43 L/Kg). The Q-Tc versus d-sotalol plasma concentration data were fitted to a model that assumed a distinct "effect compartment" and sigmoidal Emax response. The baseline Q-Tc, determined from the fittings, was found to be significantly higher in women (0.40 versus 0.38 seconds). The effect compartment clearance was found to be highly variable, with a median of 12.3 (range, 0.2-671,300) L/h. There were statistically significant differences in the effect compartment clearance by dose among men and by gender at a dose of 1.5 mg/kg. There were no significant differences detected between dose groups or genders for the d-sotalol effect site concentration at one half the maximum Q-Tc prolongation from baseline (EC50), EMAX, (the maximum Q-Tc prolongation from baseline) or the Hill coefficient. In conclusion, the pharmacokinetics of d-sotalol after intravenous administration are independent of dose and gender, because the difference between men and women in volume of distribution at steady-state is not clinically significant. The pharmacodynamics of Q-Tc prolongation produced by d-sotalol appear to be independent of dose and gender; however, there is considerable variability in the time course of effects on Q-Tc between individuals.

Fosinopril monotherapy: relationship between blood pressure reduction and time of administration.

The time to peak antihypertensive effect and the trough-to-peak ratio were determined in 64 Caucasian patients (19 men, 45 women) with mild to moderate hypertension [supine diastolic blood pressure (DBP) 95 to 115 mmHg]. They received placebo or fosinopril 10, 20, or 40 mg once daily for 4 weeks. The study consisted of a 4-week placebo lead-in, 4 weeks' double-blind treatment, and a 1-week placebo washout period. Vital signs were determined biweekly before dosing, and blood pressures were measured every 1 to 2 h during two 27-h periods at the beginning and end of treatment. After the first and last doses of all three regimens, the peak effect on blood pressure occurred 5 to 7 h after all three dosages. Neither peak nor trough blood pressure changes showed a clear dose-response relationship. Trough to peak ratios for the first dose, corrected for placebo effects, were 79% for fosinopril 10 mg, 48% for fosinopril 20 mg, and 74% for fosinopril 40 mg, and the trough-to-peak ratios for the last dose were 41% for fosinopril 10 mg, 32% for fosinopril 20 mg, and 44% for fosinopril 40 mg. In the 38 responders among the 48 patients receiving fosinopril (supine DBP decrease of at least 5 mmHg at 24 h postdose), trough-to-peak ratios ranged from 50 to 81%, and the range indicates that fosinopril is efficacious when administered once daily. Adverse effects were mild to moderate, and no patient discontinued treatment. Changes in the laboratory test results, electrocardiograms, or the results of physical examinations were unremarkable.(ABSTRACT TRUNCATED AT 250 WORDS)

Once-daily fosinopril in the treatment of hypertension.

This multicenter, dose-ranging study evaluated the antihypertensive effectiveness of once-daily administration of fosinopril sodium in 220 patients with supine diastolic blood pressure of 95-115 mm Hg. After a 4-week placebo period, patients were randomly assigned to double-blind therapy with either placebo or 10, 40, or 80 mg fosinopril once daily for 4 weeks. If treatment goals were not met, chlorthalidone 25 mg/day was added for weeks 5 to 8. Thereafter, patients could enter the long-term, open-label phase and receive 10-80 mg/day fosinopril plus chlorthalidone, if needed. After 4 weeks of monotherapy, the average decreases in supine diastolic blood pressure were 9% (10 mg), 11.5% (40 mg), and 12.5% (80 mg) compared with 6% in the placebo group. After 8 weeks, the average decreases, with or without diuretic therapy, were 12.5-18.2%, compared with 10.8% with placebo. Blood pressure continued to be well controlled, and the patients showed no evidence of tachyphylaxis or tolerance through 12-15 months of treatment. Fosinopril was well tolerated. During the short-term phase, no patient withdrew because of adverse events possibly related to fosinopril; during the long-term phase, nine of 148 patients (6.1%) withdrew for that reason. In patients with mild-to-moderate hypertension, once-daily fosinopril (40 and 80 mg) provided significant antihypertensive effects with or without diuretic therapy. The 10 mg dose was effective in some patients and may be considered a starting dose.

Effect of growth hormone on human drug metabolism: time course and substrate specificity.

Replacement therapy for six weeks with human growth hormone (hGH) in deficient children has been shown to produce a significant lengthening of amobarbital t1/2. Studies to define the time course of this effect were carried out and indicate either no change or a minimal change after one to eight days of treatment. The increased t1/2 noted at six weeks persists for at least one year. In contrast to amobarbital, theophylline was found to exhibit a shortening of t1/2 from a mean of 7.52 +/- 4.44 (SD) to a mean of 3.38 +/- 1.23 hours in four subjects. Thus, replacement therapy with hGH results in quantitatively large but opposite changes in the elimination of these two drugs. For both substrates, however, t1/2 after hGH replacement more closely resembles values reported for normal subjects. This suggests that hGH may be a major determinant of in vivo drug elimination.