Application of a system analysis approach to population pharmacokinetics and pharmacodynamics of nicardipine hydrochloride in healthy males.

Nicardipine hydrochloride, a dihydropyridine calcium channel blocker, possesses antihypertensive and arterial vasodilator properties. A system analysis approach, which makes fewer structural assumptions than compartmental methods, is presented for determining the pharmacokinetics and pharmacodynamics of nicardipine hydrochloride in healthy males following a discontinuous infusion at four dose levels. The results indicate that the average total body clearance of nicardipine is 0.920 L/h/kg and the volume of distribution is 0.275 L/kg. Nicardipine hydrochloride has a mean residence time in the body of 1.27 h, of which 0.324 h were spent in the systemic circulation and the remainder in the periphery. The determined pharmacokinetic model was linked to a pharmacodynamic model that allowed the change in the mean arterial blood pressure and heart rate to be described and predicted. A population pharmacokinetic-pharmacodynamic model was derived and the predictive power of the proposed model was assessed with a cross-validation technique that employs a relative predictive quotient for comparing the predictions to the fitted model. The results indicate that the proposed model describes the pharmacodynamics of nicardipine in healthy males and has good predictive ability when tested with a cross-validation procedure.

Nicardipine sustained release in hypertension.

1. A novel formulation of nicardipine (25% standard, 75% sustained release--SR) was evaluated in mild hypertension in a double-blind, randomized, placebo-controlled comparison with standard nicardipine (STD), using clinic measurements (Hawksley) augmented by home recorded blood pressures (Copal UA 251). 2. At 2 h after dosing (peak effect) both STD nicardipine (30 mg three times daily) and SR nicardipine (60 mg twice daily) for 28 days produced a highly significant reduction in sitting and standing blood pressure. The mean sitting blood pressure was reduced by 20/16 mm Hg (STD) and by 25/18 mm Hg (SR) compared with placebo. 3. Predose (8-11 h after last dose of STD, 12-15 h after last dose of SR) the reductions in sitting blood pressure relative to placebo were 11/6 mm Hg (STD) and 14/7 mm Hg (SR). 4. Home recordings confirmed the hypotensive effect of both formulations. Both exhibited a distinct 'peak dose' effect between 1-3 h after dosing. The effect of the SR formulation was sustained throughout the 12 h dosing interval. 5. Of the 60 patients entering the study, one died of unexplained staphylococcal septicaema, two were withdrawn for non drug-related reasons and 14 (32%) were withdrawn because of adverse effects on active therapy (headaches, facial flushing, leg oedema, chest pain, dizziness). 6. In the 43 patients who completed the study adverse symptoms were reported more frequently while they were on the two active formulations of nicardipine compared with placebo. Most of these reactions were again of vasodilator origin.(ABSTRACT TRUNCATED AT 250 WORDS)

The metabolism of nafimidone hydrochloride in the dog, primates and man.

1. The biotransformation of nafimidone, an imidazole-substituted anticonvulsant, has been studied by characterization of urinary metabolites in dogs, cynomolgus monkeys, baboons and man. 2. The biotransformation of nafimidone in these laboratory animals and man is initially very similar, in each case proceeding by reduction to the aliphatic alcohol metabolite, nafimidone alcohol or 1-[2-hydroxy-2-(2-naphthyl)ethyl]imidazole. 3. Further transformation of this metabolite involves oxidation in the naphthyl and imidazole functions, and/or conjugation. 4. The dog differs from the higher primates in that no metabolic modification of the naphthyl group takes place, the major metabolite in the dog being the O-beta-glucuronide of nafimidone alcohol. 5. In higher primates and man two isomers involving dihydroxylation in the naphthyl ring--1-[2-hydroxy-2-(5,6- or 7,8-dihydroxydihydro-2-naphthyl)ethyl]imidazole--were tentatively identified. These species alone showed evidence of an imidazole linked N-glucuronide of nafimidone alcohol. 6. The possible occurrence of stereoselective metabolism by the introduction of a chiral centre at C-9 in nafimidone alcohol was indicated in human urine by the presence of both epimers of the O-beta-glucuronide of nafimidone alcohol in a 2:1 ratio.

Comparison of the efficacy and acceptability of nicardipine and propranolol, alone and in combination, in mild to moderate hypertension.

1. We evaluated the relative efficacies and tolerability of various low-dose combinations of nicardipine and propranolol in patients with mild-moderate essential hypertension (DBP Phase V of greater than 90-125 mmHg; WHO Grades I and II) in order to select the best one. 2. Sixty patients completed the double-blind, balanced, randomised three-way cross-over protocol, with each phase lasting 4 weeks, and in which twice daily nicardipine 40 mg or propranolol 80 mg was compared with four twice daily combinations of nicardipine (20 or 30 mg) plus propranolol (40 or 80 mg). 3. At 'peak' effect time (i.e., 2 h post-dosing) all four treatment combinations were significantly more effective than propranolol, with effects ranging from 9-23 mmHg (systolic) and 5-15 mmHg (diastolic). Only the two 30 mg nicardipine combinations with propranolol were more effective than nicardipine monotherapy, further reducing BP by 8-13 mmHg (systolic) and 5-7 mmHg (diastolic); there were no significant differences between them. 4. 'Trough' diastolic pressures were not different between treatments and 'trough' BP control was sub-optimal on all treatments. 5. 70% of patients on nicardipine monotherapy, 33% of those on propranolol monotherapy and 30% of patients during the placebo run-in complained of symptoms. In terms of complaint rates, there was little to choose between the four combinations (27-33%). Serum potassium and creatinine levels were elevated following propranolol monotherapy by 0.19 mmol 1-1 and 6.5 mumol 1-1 respectively (P less than 0.01 for both) and following the nicardipine 30 mg/propranolol 80 mg combination. Nicardipine monotherapy elevated serum T4 levels by an average of 0.57 ng dl-1 (P less than 0.05). 6. The twice daily combination of nicardipine 30 mg plus propranolol 40 mg was therefore the optimum one in terms of its efficacy and tolerability. Further studies need to be performed to test the hypothesis that a higher dose of propranolol might ameliorate troublesome vasodilator side effects. However, none of the treatments studied was ideal for clinical use in the twice daily dosage used in this study.

Psychomotor effects of ketorolac in comparison with buprenorphine and diclofenac.

1. Ketorolac is an investigational non-opioid analgesic. Buprenorphine, an opioid compound and diclofenac, a non-steroidal anti-inflammatory, are analgesics used in clinical practise. 2. The psychomotor effects of ketorolac (30 mg), buprenorphine (0.3 mg), diclofenac (50 mg) and placebo all administered i.m., were examined in 12 healthy male volunteers (age 19-38 years), up to 8 h post-dose. 3. Creatine phosphokinase (CPK) was measured up to 24 h post-dose, providing an indication of local tissue damage following injection. 4. Buprenorphine caused significant psychomotor impairment in seven out of eight psychomotor tests. The effects consistently peaked 4 h post-dose and were still apparent in many cases 8 h post-dose. These psychomotor effects were supported by marked symptoms in all volunteers. 5. Ketorolac and diclofenac had no clinically significant effects on psychomotor tests and only minimal symptoms were reported. 6. Diclofenac caused a marked increased in CPK (mean Cmax 298 iu l-1) compared with ketorolac (mean Cmax 70 iu l-1) and buprenorphine (mean Cmax 68 iu l-1). 7. These results suggest that ketorolac and diclofenac are suitable for administration following day case surgery.

The metabolism of nicardipine hydrochloride in healthy male volunteers.

Four human volunteers given a 30 mg oral dose of nicardipine hydrochloride containing 40 microCi of the 14C-labelled material achieved peak plasma levels of compound-related radioactivity within one hour of dosing. Parent compound comprised only a minor fraction of the circulating radioactivity indicating rapid first-pass metabolism. Plasma radioactivity declined to background levels within 96 h and was excreted both in the urine and faeces. Urinary excretion was the favoured route comprising about 60% of the dosed radioactivity. Mean total recovered radioactivity amounted to 94.8%. Both 1,4-dihydropyridine and pyridine metabolites of nicardipine hydrochloride were excreted in the urine. The major urinary metabolites, comprising some 36% of the radioactivity excreted in the 0-8 h post-dose period, were the glucuronide conjugates of +/- 2-hydroxyethyl methyl-1,4-dihydro-2,6-dimethyl-4(m-nitrophenyl)-3,5-pyridine dicarboxylate and its pyridine from 2-hydroxyethyl methyl-2,6-dimethyl-4-(m-nitrophenyl)-3,5-pyridine dicarboxylate.

The effect of chronic treatment with a non-selective beta-adrenoceptor antagonist on the enteroinsular axis and intermediary metabolites.

In a single-blind randomized placebo-controlled cross-over study in hypertensive patients we have examined the effects of treatment with the non-selective beta-adrenoceptor antagonist nadolol on the responses of glucose, intermediary metabolites and the hormones of the enteroinsular axis to the ingestion of a mixed meal. During treatment with nadolol the plasma insulin concentration 30 min after ingesting the meal was significantly lower than on placebo and the plasma glucose rose more slowly. Plasma concentrations of GIP tended to be higher during nadolol than placebo treatment. No significant effects of treatment with nadolol were noted on pancreatic glucagon or intermediary metabolites.

The effect of nicardipine on pituitary hormone release in normal volunteers.

In a double-blind, placebo-controlled, randomised, cross-over study of six healthy male subjects, the effect of nicardipine (5 mg h-1 for 3 h) on basal and stimulated pituitary hormone release was examined. Statistically significant differences between nicardipine and placebo were seen occasionally for follicle-stimulating hormone, luteinising hormone and prolactin, but not for thyroid-stimulating hormone. These differences were always within the between-batch coefficient of variation of the assay. The overall differences in both basal and stimulated results for all four pituitary hormones were not statistically significantly different. It is concluded, therefore, that nicardipine has no significant effect on either basal or stimulated pituitary hormone release in healthy male subjects.

The effect of nicardipine on glucose and drug-stimulated insulin secretion in normal volunteers.

The effect of nicardipine on insulin secretion was examined in two double-blind, randomised, cross-over, placebo-controlled studies in normal volunteers. In the first study, the effect of acute dosing (via an intravenous infusion of 5 mg h-1 for 3 h) on the glucose, insulin, hormonal, and intermediary metabolite responses to an intravenous glucose tolerance test was determined in six healthy male volunteers. In the second study, the glucose, insulin, and C-peptide responses to intravenous tolbutamide (200 mg) was determined in another six male volunteers after oral dosing with nicardipine 30 mg three times daily for 1 week. A relative increase in insulin secretion was the principal finding of the first study. No other response was affected significantly. No significant differences between the nicardipine- and placebo-treated groups were noted in the insulin, glucose, and C-peptide measurements of the second study. In conclusion, treatment with nicardipine does not appear to impair insulin secretion in response either to an intravenous glucose load or intravenously administered tolbutamide.

The metabolism and pharmacokinetics of nicardipine hydrochloride in man.

Studies have been carried out to investigate the disposition of nicardipine hydrochloride following intravenous and oral administration to male volunteers. Following oral administration of a radiolabelled dose, nicardipine was shown to be rapidly and extensively metabolised and to be rapidly eliminated from plasma. After intravenous infusion of nicardipine at 5 mg-1 for 3 h, plasma levels declined biexponentially, and clearance values were of the same order as hepatic blood flow. With repeated oral administration, 20 mg three times daily for 28 days, plasma levels rose over the first 3 days of administration and then declined to some extent. Possible reasons for this decline are discussed. Steady-state plasma levels and bioavailability show a nonlinear relationship with doses over the range 10-40 mg three times daily. Food consumption has been shown to reduce the bioavailability of nicardipine when the food is taken before or at the same time as nicardipine administration.

Use of beta-blocking agents with group therapy in a smoking withdrawal clinic.

A controlled trial was carried out into the relative efficacy of two beta-blocking agents (oxprenolol and metoprolol) as adjuncts to group therapy in a smoking withdrawal clinic. There was no evidence to indicate that these were of specific value in assisting smoking withdrawal.

Beta adrenoceptor blockade and responses of serum lipids to a meal and to exercise.

During a randomised placebo controlled trial of the effects of nadolol in hypertensive patients serum lipid profiles were obtained while the patients were fasting and during and after a meal and an exercise test. Treatment with nadolol was associated with a significant reduction in high density lipoprotein cholesterol at all time points. Serum triglyceride concentrations during treatment with nadolol were higher in the fasting state, though not significantly so, increased further postprandially, and were significantly higher during and after exercise. The changes in high density lipoprotein cholesterol and triglyceride concentrations during beta adrenoceptor blockade may be secondary to a reduction in lipoprotein lipase activity.

Pharmacokinetics of nicardipine following oral and intravenous administration in man.

The pharmacokinetics of nicardipine have been studied following oral and intravenous administration in man and the effects of food on nicardipine kinetics investigated. Following intravenous administration of nicardipine as an infusion plasma levels declined in a biphasic manner and plasma clearance values were of the same order as hepatic plasma flow. Following oral administration in the starved state nicardipine was rapidly absorbed but subject to presystemic elimination. Maximal plasma concentrations were achieved typically between 20 minutes and 2 hours after administration. The oral bioavailability of nicardipine determined by reference to a co-administered intravenous radiolabelled dose was found to be non-linearly related to dose. Bioavailability ranged from 15-45% approximately over the dose range 10-40 mg. Administration of nicardipine following a meal reduced the bioavailability of nicardipine.