The pharmacokinetics of intravenous,intramuscular, and subcutaneous nalbuphine in healthy subjects

Summary The pharmacokinetics of intravenously, intramuscularly, and subcutaneously administered nalbuphine were studied in three parallel groups of 12 healthy volunteers each. The subjects received single doses of 10 mg and 20 mg of nalbuphine separated by a one week washout period. Blood specimens were obtained up to 15 h after dosing for determination of nalbuphine.Mean plasma nalbuphine concentrations 5 min after intravenous administration of 10 or 20 mg were 39 and 73 ng/ml, respectively. The mean maximum plasma concentrations (C_max) after intramuscular or subcutaneous administration of nalbuphine 10 mg were 29 and 31 ng/ml, respectively. Mean C_max values after 20 mg doses were 60 and 56 ng/ml. Mean C_max occurred 30 to 40 min after nalbuphine administration. The mean elimination half-lives of parenterally administered nalbuphine ranged between 2.2 and 2.6 h, regardless of dose given or route administered. The mean absolute bioavailability was 81% and 83% for the 10 and 20 mg intramuscular doses, respectively, and 79% and 76% following 10 and 20 mg of subcutaneous nalbuphine. The mean volumes of distribution (V_ss) of the intravenously administered drug were 290 and 274 l and the mean systemic clearances were 1.6 and 1.5 l/min following administration of 10 and 20 mg doses, respectively.Intramuscular and subcutaneous nalbuphine appear to be interchangeable based on the similarities in C_max, mean times until maximum concentration, mean AUC data, and absolute bioavailabilities.     

Pharmacokinetics of intravenous captopril in healthy men

Summary The pharmacokinetic characteristics of intravenously-administered captopril were investigated in 7 healthy men 20 to 33 years old. Capropril, labeled with¹⁴C, was given by injection over a 1 min period at mean doses of 2.78 mg (13.8 µCi), 5.67 mg (28.2 µCi) and 11.4 mg (56.8 µCi). Concentrations of unchanged captopril, captopril disulfide, and other metabolites (collectively) were determined in body fluids.Pharmacokinetic parameters were calculated for unchanged captopril, and it was shown that the disposition of intravenously-administered drug was linear with respect to dose over the dosage range studied.     

Dose proportionality of iopromide pharmacokinetics and tolerability after IV injection in healthy volunteers

Twelve healthy male volunteers participated in a single-blind, randomised, placebo-controlled cross-over study of IV iopromide in doses of 15 g iodine or 80 g iodine infused over a period of 15 min. The volunteers were observed for three days during which time blood samples, urine and faeces were collected.The terminal disposition phase half-life of iopromide was 2 h and 1.9 h, and the total clearance was 110 and 103 ml·min^-1 at the lower and at the higher dose levels, respectively. The steady state volume of distribution was 16 and 17 l, indicating predominantly extracellular distribution of iopromide.Statistical analysis (one-sided t-test) showed that all the target parameters (AUC, half-life and urinary excretion) were equivalent at both dose levels, indicating dose proportionate, first order kinetics of iopromide over the large dose range tested. Iopromide was well tolerated after both doses.     

Bioavailability and pharmacokinetics of oxazepam

Summary Six healthy volunteers received oxazepam 15 mg i.v. and orally at an interval of at least one week. The kinetic variables of i.v. oxazepam were: elimination half-life (t_1/2) 6.7 h, total clearance (CL) 1.07 ml·min^–1·kg^–1, volume of distribution (V_c) 0.27 l·kg^–1 (0.21–0.49) and volume of distribution at steady-state (V_ss) 0.59 l·kg^–1. The intravenous disposition of unbound oxazepam was characterized by a clearance of 22.5ml·min^–1·kg^–1 and a distribution volume of 12.3 l·kg^–1. After oral oxazepam the peak plasma level was reached in 1.7 to 2.8 h. The plasma t_1/2 at 5.8 h was not significantly different from the i.v. value. Absorption was almost complete, with a bioavailability of 92.8%. Urinary recovery was 80.0 and 71.4% of the dose after intravenous and oral administration, respectively. Renal clearance (CL_R) of the glucuronide metabolite was 1.10 ml·min^–1·kg^–1 (0.98–1.52). Oxazepam was extensively bound to plasma protein with a free fraction of 4.5%.     

Pharmacokinetics of antofloxacin hydrochloride in healthy male subjects after multiple intravenous dose administration

1. The purpose of the study was to evaluate pharmacokinetic characteristics of antofloxacin hydrochloride, a new fluoroquinolone antibiotic, during a multiple, intravenous dosing regimen.

2. Twelve healthy, Chinese male volunteer subjects were each given 300?mg of antofloxacin by intravenous infusion once daily for 7 days. Blood and urine samples were taken at designated time points for analysis of antofloxacin concentration by high-performance liquid chromatography (HPLC). Safety and tolerability were assessed by evaluation of subject complaints, vital signs, electrocardiograms, electroencephalograms, clinical chemistry parameters, haematology and urinalysis and prothrombin time.

3. The serum steady concentration of antofloxacin was obtained in 96?h after the administration of a daily intravenous dose of 300?mg of the drug. In the present study, the following pharmacokinetic parameters after 7 days of treatment with antofloxacin were determined to be: C_max 3.81?±?0.66?mg/L, C_min 0.85?±?0.19?mg/L, AUC_0–24 60.51?±?8.30?mg/L·h, C_av 2.52?±?0.35?mg/L, PTF 87.45?±?3.37%, t_1/2β 20.34?±?1.88?h. The C_max and AUC_0–24 after 7-day treatment were both higher than after the first dose (by 43% and 110%, respectively). The cumulative urinary elimination of antofloxacin within 96?h after the last dose was about 56%.

4. During the study, there were neither subject complaints nor significant adverse clinical findings.

5. Antofloxacin, administered intravenously as a single, daily 300?mg dose for 7 days, demonstrated favourable pharmacokinetic characteristics and tolerability. The results of this study indicate that antofloxacin hydrochloride is suitable for further clinical study.

     

Kinetics of ergotamine after intravenous and intramuscular administration to migraine sufferers

Summary The kinetics of ergotamine has been investigated in migrainous patients using a new, specific, sensitive HPLC assay (detection limit 100 pg/ml plasma). 10 patients were given ergotamine tartrate 0.5 mg i.v. and 5 of them received the same dose i.m. 2–3 weeks later. Blood samples were collected for up to 54 h following administration and the plasma concentration were analysed. After intravenous administration the plasma ergotamine declined rapidly, with an initial distribution half-life of 3 min followed by a mean terminal half-life of 1.86 h (range 90–155 min). The mean total plasma clearance was 11.0 ml kg^–1 min^–1, and the volume of distribution (V_d ) was 1847.6 ml kg^–1. Individual t_1/2 showed a positive linear correlation with the individual V_d . The intramuscular absorption of ergotamine was rapid and maximum plasma levels were usually obtained 10 min following administration. The biological availability was incomplete and variable at 46.6% (range 28.3–60.8%).     

Diurnal variation in the pharmacokinetics of intravenous theophylline and etophylline in healthy subjects

European Journal of Clinical Pharmacology -     

The pharmacokinetics of intravenous and oral sulpiride in healthy human subjects

Summary The pharmacokinetics of sulpiride was studied in 6 healthy volunteers after intravenous and oral (tablets) administration of 100 mg. An open two- and in two subjects a three-compartment model was applied following intravenous administration. The average total distribution volume during the terminal slope was 2.72±0.66 l/kg and total systemic clearance was 415±84 ml/min. The serum half-life of the terminal slope following intravenous administration averaged 5.3 h (range 3.7–7.1 h) according to the two-compartment model. In two subjects the half-lives were 11.0 and 13.9 h when the three-compartment model was applied. Determination of urinary excretion rates of unchanged sulpiride indicated a half-life of 7.15 h. Following intravenous administration, 70±9% of the dose was recovered unchanged in urine within 36 h; the mean renal clearance was 310±91 ml/min. Sulpiride was absorbed slowly, with peak concentrations appearing between 3 and 6 h after oral administration. The recovery of unchanged drug in urine following oral administration was 15±5% of the dose, with a mean renal clearance of 223±47 ml/min. The bioavailability determined from combined plasma and urine data was only 27±9%. The low bioavailability was probably due to incomplete absorption.     

Pharmacokinetics of nadolol in healthy subjects

Summary In 7 healthy subjects (3 males and 4 females), the kinetics of nadolol was investigated after oral doses of 60 and 120 mg. The t_1/2 was 14.0±1.8 h. The peak plasma level was doubled on doubling the dose (from 69±15 to 132±27 ng/ml, respectively) and the urinary excretion (13.5%) rose similarly. The half-life of elimination was longer at night than in the day, probably because of the slower nocturnal flow of urine.     

Dose proportionality and pharmacokinetics of dronedarone following intravenous and oral administration to rat

1. The aim of this study was to investigate the pharmacokinetic properties of dronedarone by using noncompartmental analysis and modeling approaches after intravenous and oral administration of dronedarone to rats.

2. Twenty-eight male Sprague-Dawley rats were randomly divided into four groups, and dronedarone was administered intravenously (1?mg/kg) and orally (5, 10 and 40?mg/kg) based on a parallel design. Blood samples were collected before and 0.083 (intravenous administration only), 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12 and 24?h after drug administration. The plasma concentration of dronedarone was determined by using LC-MS/MS.

3. The oral bioavailability of dronedarone was evaluated as approximately 16% in rats, similar to that in humans. The assessment of dose proportionality by using the power model showed that AUC_inf increased in a dose-proportional manner, whereas AUC_24h and C_max exhibited a lack of dose proportionality over the dose range between 5 and 40?mg/kg. The two-compartment model, with first-order absorption and elimination rate constants, was sufficient to explain the pharmacokinetics of dronedarone with biexponential decay.

4. These findings will help to understand the pharmacology of dronedarone to develop the new formulation and therapeutics optimization linked to pharmacokinetic/pharmacodynamic study.

     

Pharmacokinetics and safety of l-carnitine infused i. v. in healthy subjects

Summary The pharmacokinetics and safety of a brief i. v. infusion of l-carnitine 0, 20, 40 and 60 mg/kg have been investigated in 10 healthy subjects.The diurnal intraindividual variability of plasma carnitine was small (C. V.=3.0, 3.9 and 3.9%, respectively), and the total 24 h excretion in urine was also small and relatively constant: 4.6, 21.5 and 13.0 mg/day in the controls vs 4.6, 20.2 and 6.0 mg/day during treatment in the three subjects to whom saline alone was administered according to a single-blind design. Therefore, the pre-dose level of carnitine was subtracted from the level after dosing for the pharmacokinetic analysis. Plasma carnitine fitted well to a three-compartment open model, with Vc of 0.11–0.20 l/kg and a t_1/2 of 10–23 h. The urine recovery in 24 h was 77.2–95.4%.There were no objective or subjective side-effects attributable to carnitine, so its i. v. infusion is considered to be safe.     

Influence of repeated administration of cimetidine on the pharmacokinetics and pharmacodynamics of adinazolam in healthy subjects

Summary Adinazolam is a new triazolobenzodiazepine bearing an alkyl-amino side chain. A cross-over double-blind placebo controlled study was carried out in 12 healthy volunteers, in order to check the possible interaction between cimetidine and adinazolam after repeated co-administration.Cimetidine or placebo were given during 17 days. Beginning on Day 8 of each treatment, adinazolam was given in the increasing doses following sequence of doses for 3 days: 10 mg b.i.d., 20 mg b.i.d. and 20 mg t.i.d. A pharmacokinetic and pharmacodynamic study was performed on the third day at each dose. A wash-out of three weeks was included between the two treatments.Cimetidine increased significantly the AUC values of both adinazolam and N-desmethyladinazolam, reduced the oral clearance of adinazolam, and prolonged adinazolam's half-life.The digit symbol substitution test was significantly affected at each dose level while the manual dexterity was marginally impaired by adinazolam plus cimetidine.Saftee-up interview and Clyde mood scale indicated an increased sedation under adinazolam plus cimetidine in four subjects.     

The pharmacokinetics of tiopronin and its principal metabolite (2-mercaptopropionic acid) after oral administration to healthy volunteers

Summary We have studied the pharmacokinetics of tiopronin and its principal metabolite, 2-mercaptopropionic acid (2-MPA) in healthy volunteers after the oral administration of 500 mg (2 Acadione® tablets), followed by simultaneous assay of the two compounds in plasma over a period of 48 h using a new method (emission of fluorescence after HPLC and post-column derivatization by pyrene-maleimide). The absorption of tiopronin was slow (t_max between 4 and 6 h) and the plasma concentrations subsequently fell biexponentially. The principal metabolite 2-MPA appeared later in the plasma (t_max between 10 and 12 h after a lag-time of 3 h) then disappeared monoexponentially. About 15% of the tiopronin was metabolized to 2-MPA.     

Pharmacokinetics of cimetidine after subchronic administration

Summary The influence of cimetidine on its own pharmacokinetics after subchronic administration was assessed in 8 healthy volunteers, aged 26–29 years. On control Day 1, each subject received cimetidine 300 mg i.v., and serum and urine samples were obtained. Each subject was initiated on cimetidine 600 mg b.i.d. orally for 2 weeks. There were 3 further study days repeated after 1 and 2 weeks of cimetidine dosing and 1 week after stopping cimetidine. There was no significant difference in the mean total body clearance of cimetidine among the 4 study days. Mean elimination t_1/2 and V were similarly unchanged. However mean renal clearance (CL_R) and f_e were significantly increased following 2 weeks of drug dosing (CL_R 5.41 ml·min^–1 kg^–1; f_e 0.61) compared to control (CL_R 4.00 ml·min^–1·kg^–1; f_e 0.48). Although the non renal clearance was reduced from control values of 4.29 to 3.51 ml·min^–1·kg^–1 following 2 weeks of dosing the difference was not significant. Dosage adjustment of cimetidine appears unnecessary after short-term dosing in the presence of normal renal function.     

Pharmacokinetics of intranasal,intramuscular and intravenous glucagon in healthy subjects and diabetic patients

Summary The pharmacokinetics of intranasal, an intravenous infusion, and intramuscular glucagon has been studied in 5 healthy subjects and 11 patients with insulin-dependent diabetes mellitus.After infusion the elimination half-life was significantly longer in diabetics (11.9 vs 6.6 min) and the apparent volume of distribution was twice as high in diabetics (0.19 vs 0.37 l·kg^–1). The metabolic clearance rates were the same in the two groups (18.9 and 21.3 ml·min^–1·kg^–1 in controls and in diabetics) and were about twice those previously reported.After 1 mg intranasally the C_max of immunoractive glucagon (IRG) was similar in diabetic and in healthy subjects. Administration of a higher dose (2 mg) to diabetic patients produced a higher plasma level, although not proportionately so. The AUC after 1 mg was also similar in controls and in diabetics. The elimination half-life in both groups was similar to the value found after IV infusion; it was significantly shorter in controls (5.5 min) than in diabetics (13.8 min). In both groups, mean C_max was significantly lower than after IM glucagon, the relative bioavailability of 1 mg intranasally vs IM injection being less than 30%.After IM administration, the C_max and AUC of IRG in controls and in diabetic patients, were identical. The apparent elimination half-life was also similar in the two groups, and was three- to four-times longer (28.6 and 31.4 min) than after infusion or intranasal administration, possibly because estimation of the t_1/2 was affected by slow release of the hormone from the site of injection.     

The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous,intramuscular, and subcutaneous injection

Summary The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 g lisuride hydrogen maleate as an aqueous solution.After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml·min^–1·kg^–1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration.The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.     

Effects of liver disease on the pharmacokinetics of intravenous and oral chlordesmethyldiazepam

We studied the pharmacokinetics of a single 0.5-mg i.v. dose of chlordesmethyldiazepam in 8 patients with liver disease and in 12 age-matched healthy controls. The kinetics were also studied of a single 1-mg oral dose in the patients with liver disease. After i.v. administration the kinetics of total chlordesmethyldiazepam in patients with liver disease differed from those in controls: elimination half-life was almost twice that in controls (395 and 204 h), as a consequence of a marked reduction in total clearance (0.13 and 0.25 ng·ml^–1·h^–1), whereas the apparent volume of distribution was similar in patients and controls (4.7 and 3.9 1/kg^–1). The free fraction of the drug in patients was higher (5.5%) than in controls (2.9%). Correction for differences in protein binding revealed clearance in the patients was one-fifth (1.8 and 10.5 ng ml^–1·kg^–1) and volume of distribution one-half (65.0 and 118.4 1·kg^–1) that in controls. The systemic availability of oral chlordesmethyldiazepam was high (110%) in spite of a relatively slow absorption rate. These results indicate a need for caution in the administration of chlordesmethyldiazepam to patients with liver disease.     

Separate and combined effects of nadolol and nifedipine on the cardiac response to exercise

Summary In a placebo controlled exercise protocol using healthy volunteers the effects of nadolol 80 mg and 160 mg orally and of nadolol 80 mg during treatment with nifedipine 20 mg 8 hourly were compared. Resting systolic and diastolic blood pressures were reduced by both nifedipine (p<0.05) and nadolol (p<0.01) acting alone. An unexpected finding was that nifedipine alone significantly inhibited exercise tachycardia (p<0.01) (8 to 12 h post dose). Predictably both doses of nadolol produced significant reduction in exercise tachycardia which was still apparent at 24 h. There was a linear relationship between log₁₀ plasma nadolol concentration and reduction in exercise heart rate. The combined inhibitory effects of nifedipine and nadolol 80 mg on exercise heart rate showed partial additivity but did not summate. There was no pharmacokinetic interaction between the 2 drugs. The inhibition of exercise tachycardia by nifedipine, not previously documented, is consistent with an effect of the drug on the sinus node, as has been reported in in-vitro studies, and may contribute to the drugs efficacy in angina.     

Venoconstrictor effects of dihydroergotamine after intranasal and intramuscular administration

Summary A parenteral formulation of dihydroergotamine (DHE) is the only galenical form now available for the treatment of acute attacks of migraine in which a rapid onset of action is required. A recently developed nasal spray of DHE has been compared with intramuscular DHE for its venoconstrictor activity. In a randomised double-blind, cross-over trial, 9 healthy male volunteers received a single dose of DHE 1 mg intranasally, DHE 0.5 mg i.m. or placebo (intranasally and i.m.) on three different occasions, with an interval of at least 1 week between doses. Both active treatments, but not placebo, produced marked venoconstriction as shown by reduced compliance of superficial hand veins. The effect persisted for more than 8 h. The maximum venoconstrictor effect of 1 mg DHE intransally was 40±12% (mean ± SEM) and after 0.5 mg i.m. it was 52±15%. The time course of the venoconstrictor effect was similar after both routes of administration. Blood pressure and heart rate changes in these normotensive subjects were almost identical after dihydroergotamine and placebo. The results suggest that the nasal spray could be used as an alternative to parenteral DHE, permitting self-administration of the drug for the treatment of acute attacks of migraine.     

Inhibition of soluble catechol-O-methyltransferase and single-dose pharmacokinetics after oral and intravenous administration of entacapone

The inhibition of soluble catechol-O-methyltransferase (S-COMT) in red blood cells (RBCs) by entacapone, and the pharmacokinetics of entacapone after single oral (5–800 mg) and IV (25 mg) doses have been examined in an open study in 12 healthy young male volunteers.Oral entacapone dose-dependently decreased the activity of S-COMT in RBCs with a maximum inhibition of 82% after the highest dose (800 mg). The inhibition of S-COMT in RBCs was reversible and the activity recovered within 4–8 h.Entacapone showed linear pharmacokinetics over the dose range studied: C_max and AUC were correlated with the dose of the drug. Oral absorption of entacapone was fast, with a t_max ranging from 0.4 to 0.9 h, depending on the dose. Systemic availability of entacapone varied between 30 and 46%. Entacapone was rapidly eliminated by metabolism with a half-life of 0.27–0.30 h after oral doses of 5 to 50 mg. After doses from 100 to 800 mg the disposition was best described by two phases with a t_1/2 of 0.27–0.37 h and t_1/2 of 1.59–3.44 h.Over the dose range studied, the single oral and IV doses of entacapone were well tolerated. No haematological, biochemical or haemodynamic adverse effects were seen.The results show that entacapone is an orally effective and reversible COMT inhibitor in man and has simple, linear pharmacokinetics.