Total and free steady-state plasma levels and pharmacokinetics of nifedipine in patients with terminal renal failure

Summary The total and free steady-state plasma levels of nifedipine in patients with renal failure have been compared with those in subjects with normal renal function. Studies were done after administration of nifedipine 10 mg t.d.s. p.o. for 5 days, after i.v. infusion of 4·4 mg, and after a single 10 mg oral dose.The systemic clearance of nifedipine after a single i.v.-dose was higher in subjects with renal insufficiency (854 ml/min) than in those with normal renal function (468 ml/min). After the single oral dose the AUC (6100 ng·min·ml^–1) and maximum plasma concentration (75.0 ng·ml^–1) were lower than in subjects with normal renal function (19300 ng·ml^–1; 122 ng·ml^–1). The plasma protein binding of nifedipine averaged 95.5% in normal subjects and 94.8% in patients with renal failure.Although free and total steady-state plasma levels of nifedipine tended to be somewhat lower than normal in renal failure, the changes in pharmacokinetics and decreased protein binding of nifedipine did not result in a significantly different steady-state plasma level of the drug. The blood pressure response to a given plasma nifedipine level appeared to be enhanced in renal failure.     

Pharmacokinetics of oral salbutamol controlled-release in Asian patients with asthma

Summary Using a double blind, double dummy crossover design, single dose and steady state pharmacokinetics of oral controlled release (SCR) salbutamol 4 mg and 8 mg tablets b. d. has been studied in 8 Asian patients.Plasma salbutamol was measured over 12 h. In 8 patients the single dose mean C_max was 4.2 ng·ml^–1 and 7.7 ng·ml^–1 after 4 and 8 mg, respectively. In 5 patients the steady state mean C_max, C_min and t_max were 8.1 ng·ml^–1 and 4.7 ng·ml^–1 and 6 h for the 4 mg tablets and 14.1 ng·ml^–1 and 7.1 ng·ml^–1 and 4 h for the 8 mg tablets.It is concluded that both doses of SCR show features of controlled release and that they produced a relatively constant plasma level of salbutamol in Asian patients.     

Single dose pharmacokinetics of proguanil and its metabolites in pregnancy

Summary Plasma and whole blood concentrations of proguanil, its active metabolite cycloguanil, and the inactive metabolite 4-chlorophenyl-biguanide, were measured by HPLC in 10 healthy Karen women in the last trimester of pregnancy, following a 200 mg single oral dose of proguanil. Four of these women were restudied 2 months after delivery.The pharmacokinetic properties of proguanil were similar during and after pregnancy. Median peak plasma concentrations of proguanil during pregnancy and following delivery were 212 and 215 ng·ml^–1, and occurred at 4.5 and 5 h, respectively. Mean plasma AUC values for proguanil during and following pregnancy were 94 and 98 ng·h·ml^–1·kg^–1, respectively. Corresponding whole blood AUC values were 361 and 396 ng·h·ml^–1·kg^–1. The mean elimination half lives and mean residence times of proguanil in plasma and whole blood were 12.3 and 19.6 h and 13.8 and 20.7 h respectively during pregnancy. Following pregnancy these values were 17.1 and 19.7 h for plasma and 19.7 h and 20.2 h for whole blood respectively.Mean peak plasma and whole blood concentrations of cycloguanil following pregnancy were 25 and 22 ng·ml^–1 respectively. During pregnancy peak cycloguanil concentrations in both plasma and whole blood were markedly lower, 13 and 12 ng ml^–1, respectively. Two pregnant women (neither of whom were restudied) were probably poor metabolisers of proguanil. The mean ratio of proguanil to cycloguanil plasma AUC was 16.7 in the third trimester of pregnancy and 7.8 following pregnancy, compared with less than 5 in previously reported studies. The concentrations of 4-chlorophenylbiguanide in both plasma and whole blood in pregnant subjects were also lower than those after pregnancy.These data show that blood concentrations of the active antimalarial metabolite cycloguanil are reduced in late pregnancy and that the currently recommended dose of proguanil could be inadequate for antimalarial prophylaxis in pregnant women.     

Pharmacokinetics of methadone and its primary metabolite in 20 opiate addicts

In a closed metabolic ward the pharmacokinetics of methadone and its primary metabolite (EDDP) were studied in 20 long-term opiate addicts. After administration of the daily oral dose of methadone HCl (mean 60 mg, range 10–225 mg) blood samples were taken and analysed, using a newly developed high-performance liquid chromatography (HPLC) method. The steady-state plasma concentrations of the 20 subjects varied from 65–630 ng·ml^–1 and from 5 to 55 ng·ml^–1, whereas the peak concentrations were 124–1255 ng·ml^–1 and 10 – 301 ng·ml^–1 for methadone and EDDP, respectively. The calculated ratios between the area under the curve (AUC_{(0–24 h)}) for methadone and the AUC_{(0–24 h)} for EDDP varied from 5.9 to 44.6, indicating interindividual differences in metabolic activity. In 19 out of 20 subjects the pharmacokinetics of methadone are best described using a two-compartment model. The mean body clearance was 1.64 ml·min^–1·kg^–1, whereas the mean elimination rate constant () and plasma half-life (t _1/2) were 0.026·h^–1 (range 0.013–0.053·h^–1) and 31.2 h (range 13–53 h), respectively. Differences of gender were also found. A poor correlation was found between the methadone dose and the steady-state level. A much better correlation was found between the normalized steady-state level and the body clearance.     

A double-blind placebo controlled dose response study of noberastine on histamine induced weal and flare

Summary The antihistaminic effects of 7 days treatment with each of three doses of noberastine (10, 20 and 30 mg) were compared to placebo in 12 healthy male volunteers. The antihistaminic activity was assessed from the inhibition of weal and flare formation after intradermal histamine injections. For both weal and flare there was a highly significant effect of treatment with each of the three doses of noberastine, compared to placebo. The 30 mg daily dose produced the maximum inhibition of weal and flare. The daily mean values for the assessment of sedation by visual analogue scales at 09.00 h, 15.00 h and 21.00 h showed no significant treatment, or order, effect for any of the three doses of noberastine compared to placebo. The mean steady-state plasma concentrations of noberastine were significantly higher with increasing daily doses of noberastine (trough concentrations: 1.0, 1.6 and 2.2 ng·ml^–1; peak concentrations: 3.5, 13.4 and 20.9 ng·ml^–1 for 10, 20 and 30 mg daily dose, respectively). The percentage weal inhibition correlated (r=0.77) with steady-state noberastine plasma trough levels. The percentage flare inhibition showed a weaker correlation (r=0.35) with steady-state noberastine plasma trough levels.     

The pharmacokinetics of amiloride-hydrochlorothiazide combination in the young and elderly

Summary The pharmacokinetics of amiloride and hydrochlorothiazide were studied in 12 healthy young volunteers following a single dose of a fixed combination of amiloride and hydrochlorothiazide and in 11 elderly hypertensive patients at steady-state. Following modelling of the single dose data, simulated steady-state plasma concentrations for the 2 drugs were generated to examine the effect of age and/or hypertension on pharmacokinetics.The apparent systemic plasma clearance for both amiloride and hydrochlorothiazide was significantly reduced in the elderly when compared to the young (from 753 to 325 ml·min^–1, amiloride; and from 418 to 157 ml·min^–1, hydrochlorothiazide). The plasma concentrations at steady state for both drugs were greatly increased in the elderly patients (Amiloride: from 7 to 25 ng·ml^–1, C_ss,max; from 2 to 8 ng·ml^–1, C_ss,min; and from 4 to 14 ng·ml^–1, C_av; Hydrochlorothiazide: from 184 to 651 ng·ml^–1, C_ss,max; from 31 to 121 ng·ml^–1, C_ss,min; and from 89 to 273 ng·ml^–1, C_av).The decreased clearance of the diuretics in the elderly was believed due to deterioration of renal function, and there was a significant correlation between the plasma clearance of hydrochlorothiazide and creatinine clearance in both age groups (r=0.62, young;r=0.72, elderly).As a result of the pharmacokinetic findings caution may be indicated in the clinical dosage of the diuretics particularly when in fixed dose combination.     

The tolerability,pharmacokinetics and lack of effect on plasma cholesterol of 447C88, an AcylCoA:Cholesterol Acyl Transferase (ACAT) inhibitor with low bioavailability,in healthy volunteers

447C88 (N-Heptyl-N-(2,4 difluoro-4-6-(2(-4-(2,2 dimethylpropyl)phenyl)ethyl)phenyl)urea) is an inhibitor of human microsomal AcylCoA:Cholesterol acyltransferase (ACAT) with an IC₅₀ of 10.2 ng·ml^–1 (23 nM). It is poorly absorbed but 5 mg·kg^–1·day^–1 completely abolishes the rise in plasma cholesterol in cholesterol-fed rats.In this study, twelve healthy, male volunteers received single, oral doses of 25, 50, 100, 200, 400 and 800 mg of 447C88 (n+8) or placebo (n+4) with food in a double-blind study with at least a week between occasions. The 400 mg dose was repeated after an overnight fast. Subsequently, fourteen different volunteers received a single 200 mg dose of 447C88 (n+8) or placebo (n+6) with food and, a week later, the same dose twice daily for 10 days; all doses were given with food.All doses were well tolerated with no significant changes in vital signs, full blood counts or plasma biochemical profiles. Plasma concentrations of 447C88 were unquantifiable after the fasting dose and low after all other doses. Mean C_max and AUC were 1.8 ng·ml^–1 and 9.0 ng·ml^–1·h after 200 mg rising to 5.4 ng·ml^–1 and 23.8 ng·ml^–1·h respectively after 800 mg; t_1/2 was 1.3 to 5.2 h. After 10 days dosing, plasma 447C88 concentrations were higher in the evening than the morning probably due to administration of the evening dose with more food. There were no significant changes in plasma triglcerides or total, LDL- or HDL-cholesterol after dosing with 447C88.     

Plasma concentrations and haemodynamic effects of nimodipine in patients resuscitated after cardiac arrest

Summary As the pharmacokinetics of a drug may be altered in haemodynamically compromised patients, the plasma concentrations and haemodynamic effects of the calcium entry blocker nimodipine have been examined in patients resuscitated after out-of-hospital cardiac arrest.In 7 patients nimodipine was infused at increasing rates up to 30 µg·kg^–1·h^–1. The plasma concentrations increased with increasing dose; at the highest dose a mean steady-state plasma concentration of 22.1 ng·ml^–1 was obtained, and the mean plasma clearance was 1.4 l·kg^–1·h^–1. There were no marked changes in mean arterial blood pressure or heart rate.In 9 other patients nimodipine was given as a bolus infusion of 10 µg·kg^–1 over 3 min, followed by a continuous infusion of 30 µg·kg^–1·h^–1. A mean steady-state plasma concentration of 17.6 ng·ml^–1 was obtained and the mean plasma clearance was 1.9 l·kg^–1·h^–1. Heart rate did not change significantly, but the mean arterial blood pressure fell.The data indicate that in patients resuscitated after cardiac arrest, the pharmacokinetics of nimodipine are not markedly different from patients with other conditions, e.g. subarachnoid haemorrhage. However, if a loading dose is given to obtain a steady-state concentration sooner, there will be a fall in arterial blood pressure.     

The pharmacokinetics of ketanserin after a single dose and at steady-state in hypertensive subjects

Summary We have studied the pharmacokinetics of ketanserin in 6 hypertensive patients after a single oral 40 mg dose and at steady-state after 4 weeks treatment with 20 mg and then 40 mg 12-hourly.Pharmacokinetic variables after a single dose were similar to those reported in healthy volunteers, with median values for C_max 112 ng·ml^–1, t_max 1 h, and t_1/2 19 h. The corresponding values for the metabolite ketanserinol were C_max 155 ng·ml^–1, t_max 2 h, and t_1/2 25 h. The median AUC was 3.3 times greater for ketanserinol than for the parent drug.These results were used to predict the mean steady-state plasma concentrations of ketanserin and ketanserinol. Predicted values were on average similar to those observed after four weeks treatment with 40 mg 12-hourly, although there were marked differences between the observed and predicted values in some patients.There was no evidence of time- or dose-dependent kinetics for ketanserin, but the study had insufficient power to exclude the occurrence of these phenomena entirely.     

Pharmacokinetics of verapamil in patients with hypertension

Summary Twelve hypertensive patients (WHO Stage I-II) were given oral verapamil (Isoptin) b.d. or t.d.s. as long-term treatment. The pharmacokinetics of verapamil and norverapamil were studied both after single and b.d. and t.d.s. doses of verapamil 240, 360 or 480 mg daily adjusted according to the blood pressure response. The apparent oral clearance of verapamil was decreased after both the twice and thrice daily dosage regimens (1.38 and 1.841/min, respectively) as compared to the single dose (4.39 l/min). The plasma half-life of verapamil was increased from 3.34 h (single dose) to 4.65 h (b.i.d.). Decreased elimination of norverapamil was also found after multiple doses of verapamil, as shown by an increase in the adjusted AUC of norverapamil (adjusted to a verapamil dose of 80 mg), namely from 574.9 h·ng·ml^–1 (single dose) to 1172 h·ng·ml^–1 (b.d.) and to 841 h·ng·ml^–1 (t.d.s.). The plasma half-life of norverapamil increase from 5.68 h to 7.34 h during twice daily dosing. During thrice daily verapamil, no increase in plasma half-life was found either for verapamil or norverapamil, probably due to the relatively short sampling time (6 h). The plasma concentration of verapamil and the reduction in supine systolic and diastolic blood pressure were correlated. The mean decrease in supine systolic blood pressure was 5.8 mm Hg per 100 ng verapamil/ml plasma, and for diastolic pressure 2.9 mm Hg per 100 ng verapamil/ml plasma. The mean steadystate plasma concentrations of verapamil were similar after twice and thrice daily dosing regimens, which agrees with the clinical observation that blood pressure control in hypertensive patients is as good after verapamil b.d. and t.d.s.     

Pharmacokinetics and dialysability of isradipine in chronic haemodialysis patients

Summary The pharmacokinetics of isradipine, a calcium-channel blocker, have been studied in eight patients on chronic haemodialysis. A single oral dose of 5 mg was administered on both a non-haemodialysis and a haemodialysis day and the plasma concentrations of isradipine were analyzed.The mean c_max, t_max, AUC, and t_1/2 in plasma on the non-haemodialysis day were 5.2 ng·ml^–1, 1.4 h, 23.8 ng·h·ml^–1, and 3.1 h, respectively. The dialysis clearance of isradipine was negligible (5.0 ml·min^–1).The t_1/2 values during haemodialysis were not significantly different from those observed during the same period post dose on the non-haemodialysis day. The study demonstrates that supplemental doses of isradipine are not necessary in these patients since isradipine is not significantly removed by haemodialysis.     

Pharmacokinetics and pharmacodynamics of ramipril and piretanide administered alone and in combination

The pharmacokinetics and pharmacodynamics of single oral doses of 5 mg ramipril and 6 mg piretanide administered separately and in combination were determined in a single blind, randomised, 3-period cross-over study in 24 healthy male volunteers.The peak plasma concentrations of ramipril and ramiprilat increased slightly (from 11.9 to 14.8 ng/ml, and from 6.39 to 8.96 ng/ml, respectively) as did the area under the plasma concentration-time curve of ramipril (0–4 h) and ramiprilat (0–24 h) (from 15.8 to 19.8 ng·ml^–1·h, and from 63.4 to 74.6 ng·ml^–1·h, respectively). The urinary excretion of ramiprilat also rose (from 6.82 to 7.73 % of dose) following simultaneous treatment with piretanide. These effects were probably due to reduced first-pass metabolism of ramipril/ramiprilat to inactive metabolites. The blood pressure lowering effect, the time course of inhibition of ACE activity in plasma and the concentration-response relationship for the inhibition of plasma ACE activity were not affected by piretanide.The peak plasma concentration of piretanide was somewhat reduced (from 285 to 244 ng/ml) following simultaneous treatment with ramipril. No other pharmacokinetic parameter was affected. Piretanide increased urine flow, and sodium, chloride and potassium excretion, especially during the first 2 hours following administration. These pharmacodynamic parameters were not affected by ramipril.Thus, simultaneous administration of single oral doses of ramipril and piretanide caused modest changes in the peak and average plasma concentrations of both drugs, which did not lead to detectable alterations in the pharmacodynamic parameters measured in healthy volunteers.     

Studies on hydralazine

Summary After oral administration of a single 50 mg dose of hydralazine (Apresoline^®), the serum half-life (T1/2) and bioavailability (AUC_0–) were assessed in 16 healthy volunteers. The half-life was 2.57±0.14 h (S.E.) in 10 slow acetylators of sulphadimidine, and 2.18±0.15 h in 6 fast acetylators (difference not statistically significant). AUC_0– was significantly higher in slow acetylators, at 1.04±0.10 µg·hour·ml^–1, compared to 0.66±0.12 µg·hour·ml^–1 in the fast acetylators (p<0.025). Treatment with Apresoline^® 25 mg tid produced minimum serum concentrations at steady-state of 57.3±7.3 ng·ml^–1 and 33.4±4.2 ng·ml^–1 in 8 slow and 5 fast acetylators, respectively (p<0.05). The corresponding maximum concentrations were 228.8±20.3 ng·ml^–1 and 147.6±15.0 ng·ml^–1 in slow and fast acetylators, respectively (p<0.025). First-pass metabolism of hydralazine could explain the difference in bioavailability of the drug between fast and slow acetylators, without any corresponding difference in the elimination rate of the drug in the post-distributive phase.     

The excretion of ketorolac tromethamine into breast milk after multiple oral dosing

Summary We have studied the transfer of the analgesic ketorolac tromethamine into breast milk in ten women aged between 22 and 35 years. Ketorolac administration was started between 2 and 6 days after delivery. The breast milk was not fed to the infant because of maternal antibiotic use (6 patients) or because of jaundice of the baby.10 mg of ketorolac was given four times daily for two days. Plasma and milk samples were collected on the two dosing days and on the first day after dosing. The plasma and milk were assayed for ketorolac concentrations by HPLC; the quantification limits were 10 ng·ml^–1 and 5 ng·ml^–1 respectively.The maternal plasma concentrations were within established ranges for ketorolac. In four patients the concentration of ketorolac in the milk was never above 5 ng·ml^–1. At 2 h after dosing on both Days 1 and 2 there were quantifiable concentrations of ketorolac in the milk. The range was 5.2 ng·ml^–1 to 7.9 ng·ml^–1. The ratio of breast milk: plasma concentrations of ketorolac ranged from 0.015 to 0.037.The maximum potential amount of ketorolac that an infant may be exposed to daily could range from 3.16 mg to 7.9 mg, assuming a consumption of between 400 ml and 1 l of breast milk. On a weight-adjusted basis this is equivalent to between 0.16% and 0.40% of the total daily maternal dose.Klinikum der Stadt Mannheim, Gynaecological Clinic, Mannheim, (until 1986: Krankenanstalt Rotes Kreuz, Munich)     

Single and multiple dose pharmacokinetics of tenoxicam in the elderly

Summary Fourteen elderly subjects (10 women, 4 men) with a mean age of 81 (SD 6.7) years and in need of anti-inflammatory drug treatment were given a single dose of 20 mg tenoxicam. After a drug-free interval of 5 weeks, multiple dose treatment with 20 mg tenoxicam once daily for 56 days was initiated. The single and multiple dose kinetics of tenoxicam were investigated after HPLC determination of tenoxicam in the plasma.The elimination half-life of tenoxicam ranged from 44 to 132 h (mean 71.9 h) with no significant difference between the single and multiple dosage regimens. Tenoxicam reached maximum plasma concentrations after 1.4 and 1.1 h, with values of 3.6 and 15.5 µg·ml^–1, for the single and multiple dosage regimen respectively. The corresponding trough values (24-h values) were 1.8 and 11.7 µg·ml^–1. A mean accumulation ratio of 5.1 was calculated. The mean increase in the area under the plasma concentration time curves at steady-state was 21% more than predicted from the initial single dose. This deviation from linearity was considered to be of minor clinical significance. The kinetics of tenoxicam in elderly were similar to that published for young healthy volunteers.     

Nitrendipine in human plasma and breast milk

Summary To assess the disposition of the dihydropyridine calcium antagonist, nitrendipine, in lactating mothers, we studied three breast-feeding women to determine simultaneous plasma and breast milk concentrations of nitrendipine and its inactive pyridine analog metabolite after both a single 10 mg oral dose and 5 days of continuous therapy (20 mg per day).Nitrendipine was excreted in breast milk at peak concentrations ranging from 4.3 to 6.5 ng/ml 1–2 h after acute dosing while its inactive pyridine metabolite ranged from 6.9 to 11.9 ng·ml^–1. After 5 days of dosing, C_max remained in the same range and the breast milk/whole plasma concentration ratio for nitrendipine was 0.2 to 0.5. On the fourth day of continuous dosing, average concentrations of nitrendipine from 24-h collections of the milk were 1.1 to 3.8 ng·ml^–1.Thus, nitrendipine and its metabolite are excreted in very low concentrations in human breast milk. Based on a maternal dose of 20 mg daily, a newborn infant would ingest an average of 1.7 µg of nitrendipine per day, or a relative dose of 0.095%.Presented in part at the 3rd Annual Meeting of the American Society of Hypertension, New York, N.Y., June 24, 1988     

Single dose and steady-state pharmacokinetics of 4 mg and 8 mg oral salbutamol controlled-release in patients with bronchial asthma

Summary Fifteen patients with asthma were given salbutamol controlled-release (SCR) 4 mg or 8 mg twice daily for seven days, in a randomised double-blind cross-over design. Plasma salbutamol levels were measured after the first and fifteenth doses for a 12 h period following drug ingestion.At steady-state the geometric mean values for C_max were 8.2 ng/ml for 4 mg, and 16.1 ng/ml for 8 mg. Median t_max values were 300 and 240 min respectively. The geometric mean AUC (0–12) were 4507 ng·min·ml^–1 and 8980 ng·min/ml. Peak to trough fluctuation ratios were 0.577 and 0.572.There were no significant differences between 4 mg or 8 mg formulations, for any of the parameters measured, after appropriate corrections for dose. The concentration-time profiles at steady-state showed little fluctuation in plasma salbutamol levels over the twelve hour dosing interval. These results show that 4 mg and 8 mg formulations of SCR provide smooth plasma profiles at steady-state with a twice daily dosing regime.Part of this paper has been presented in abstract form to the British Thoracic Society, Newcastle, July 1988     

Interaction of talinolol and sulfasalazine in the human gastrointestinal tract

Summary The absorption of talinolol (TA) 50 mg was investigated without and together with the co-administration of sulfasalazine (SASP) 4 g in 11 healthy young volunteers, in order to clarify gastrointestinal transit of TA.Without SASP, the t_max of TA was 2.8 h, C_max was 112 ng·ml^–1 and the half life was 12 h; the AUC_o-t was 958 ng·ml^–1·h.In the case of concomitant administration of SASP, TA was found only in serum from 3 individuals, with a C_max of 23 ng·ml^–1 and a mean AUC_o-t of 84 ng·ml^–1·h. TA was not detectable in 5 subjects and it was at the limit of detection (2 ng·ml^–1) in 3 subjects. Pharmacokinetic analysis was not possible in any of those individuals.The reason for the interaction appears to be the adsorption of TA by SASP. An interval of 2–3 h should elapse between giving SASP and other drugs.     

Pharmacokinetics and pharmacodynamics of propafenone during acute and chronic administration

Summary The pharmacokinetics of propafenone and 5-OH-propafenone and their relationship with the antiarrhythmic action and side effects have been studied in 10 patients with stable, frequent, premature ventricular beats (224–928 premature ventricular complexes/h). Observations were made after a single dose of propafenone 300 mg p.o., and after 1 and 3 months (only 5 out of 10 patients) of therapy with 300 mg t.d.s.After 1 month of treatment the plasma elimination half-life of propafenone (6.7 h) was almost twice as long as after a single dose (3.5 h), and the area under the plasma propafenone concentration-time curve (7620 ng·ml^–1·h) was significantly larger than after single dose (3522 ng·ml^–1·h); this was also true for the metabolite. The ratio of the AUCs of 5-OH-propafenone and propafenone decreased from the single dose (0.63) to 1 month (0.32). These variables remained stable up to 3 months.Eight patients had 75% reduction of premature ventricular complexes after 3 days of therapy, and in 7 they were completely suppressed; the response was maintained over 1 to 3 months. Side effects were minor and in no case had the drug to be withdrawn or the dose reduced.Thus, the kinetics of propafenone were time-dependent. Its active metabolite did not accumulate greatly during chronic treatment. The lasting antiarrhythmic effect observed in some patients suggests a b.d.s. regimen instead of t.d.s. dosing in selected patients.     

A lack of pharmacokinetic interaction between ranitidine and piroxicam

Summary The effects of piroxicam (40 mg) on the pharmacokinetics of ranitidine (150 mg) and of ranitidine (150 mg bid) on the pharmacokinetics of piroxicam (20 mg) were assessed in two 2-way crossover studies in two groups of 18 healthy male subjects.In the first study there were no statistically significant differences between the pharmacokinetic variables for ranitidine in the presence or absence of piroxicam. The mean maximum plasma concentration (C_max) was 467 ng·ml^–1 for ranitidine alone and 466 ng·ml^–1 in the presence of piroxicam; mean area under the plasma concentration vs time curve (AUC) was 2460 h·ng ml^–1 and 2551 h·ng ml^–1 respectively; and the mean terminal half-life (t 1/2) was 3.6 h and 3.8 h respectively.In the second study there were no statistically significant differences between the pharmacokinetic variables for piroxicam in the presence or absence of ranitidine. The mean C_max was 2.1 ·ml^–1 in the presence of placebo and 2.0 g·ml^–1 in the presence of ranitidine respectively; mean AUC was 133 h·g ml^–1 and 137 h·g ml^–1 respectively, and the mean t 1/2 was 53.6 h and 54.5 h respectively.