Pharmacokinetics of isoxsuprine hydrochloride administered orally and intramuscularly to female healthy volunteers.

Isoxsuprine (1-(4-hydroxyphenyl)-2-(1-methyl-2-phenoxyethylamino)-1-propanol, CAS 395-28-8) is a peripheral vasodilator that also stimulates beta-adrenergic receptors. It causes a direct relaxation of vascular and uterine smooth muscles and produces positive inotropic and chronotropic effects. It is widely used to arrest premature labour and miscarriage. The aim of this trial was to investigate the pharmacokinetics of isoxsuprine hydrochloride administered orally to healthy young female volunteers as an extended-release formulation at the doses of 30, 60 and 90 mg compared to 10 mg by i.m. route. A randomised, crossover, four-period, multisequence, single-dose design was adopted. Plasma and urine concentrations of free and total isoxsuprine were evaluated by tandem mass spectrometry that reached a low quantification limit of 1 ng/ml. From plasma concentrations Cmax, tmax, AUC(0-t), AUC(0-infinity), t1/2 and Vd and from urine concentration CUE(0-24h) were evaluated by the non-compartmental model. The free drug was present only in plasma after i.m. route, whereas total isoxsuprine, namely the drug after an enzymatic hydrolysis of the conjugate form, was detected in all plasma and urine samples. The distribution volume of the free drug proved to be 2.5 times higher than that of total isoxsuprine, which indicates a good penetration of the free drug into tissue compartments. Oral absorption was evaluated from the p.o./i.m. percentualized ratio of AUC and CUE and proved to be on average around 51%, being linearly correlated with the three doses administered. The oral absorption proved to be sustained as expected from the zero-order kinetics of the drug release from the core of the extended-release formulation. This has justified different values of half-life that was on average 2.2 h after the i.m. route and around 10 h after the three oral doses. After isoxsuprine administration, both oral and i.m. routes, the heart rate increased from baseline during the 9 h monitoring period. This was an expected finding attributable to the stimulating activity of beta-adrenergic receptors. The tolerability of isoxsuprine proved to be very good with all the four administrations performed.

Bioassay of safinamide in biological fluids of humans and various animal species.

This paper describes three methods to bioassay safinamide (CAS 133865-89-1) in biological fluids of humans and laboratory animals for pharmacokinetic, toxicokinetic and bioavailability studies. Two methods profited from liquid chromatography tandem mass spectrometry (LC-MS-MS) system, one (micro bioassay) working in the low dynamic range 0.5-20 ng/ml, the other in the range 20-6000 ng/ml. A third method used high-performance liquid chromatrography with fluorimetric detection (HPLC-FD), working in the dynamic range 20-1000 ng/ml. All the three methods were validated in compliance with the accreditated views on analytical bioassays. The shorter run time (5.5 min vs 16 min) has led the authors to prefer the two LC-MS-MS methods to the HPLC-FD bioassay, even if all the performances of the three methods were excellent. The methods described in this paper were and are still now extensively used to assay safinamide in more than 10,000 specimens of biological fluids from humans and laboratory animals in the development program of the drug. Main pharmacokinetic results obtained in various Phase I trials on healthy volunteers are briefly reported.

Bioequivalence study of fluoxetine hydrochloride in healthy volunteers.

Fluoxetine hydrochloride (CAS 59333-67-4) is a selective serotonin reuptake inhibitor (SSRI) widely used as antidepressant drug. The aim of the present trial was to assess the bioequivalence of a new formulation of the drug (test formulation) as compared to a reference product from the Swiss market. Both drugs were available as 20 mg dispersible tablets. The trial was performed according to a two-period, two-sequence, balanced, randomised, single-dose design with a wash-out phase of at least 56 days. The two formulations were tested in 30 male healthy volunteers. A specific highly sensitive bioassay in tandem mass spectrometry allowed to set the limit of quantification to 100 pg/ml for fluoxetine and norfluoxetine. Average t(max) was 5.4 h for fluoxetine and 71-80 h for norfluoxetine. The peak concentration was on average 14 ng/ml for fluoxetine and 10.5 ng/ml for norfluoxetine. Half-life was on average 48-50 h for fluoxetine and 130-138 h for norfluoxetine. AUC infinity for fluoxetine and norfluoxetine were on average 790 and 2800 ng x ml(-1) x h, respectively. All these figures demonstrate that plasma concentration-time profiles of fluoxetine and norfluoxetine are quite different. Applied statistical tests, suggested by operating guidelines, demonstrated bioequivalence of the test formulation and the reference formulation. The conclusion on bioequivalence was based on both fluoxetine and norfluoxetine results. 90 % confidence Intervals for Cmax, AUCt and AUC infinity (fluoxetine and norfluoxetine) were within the acceptance range (0.80-1.25) and t(max), processed with a non-parametric test, did not show any statistically significant difference between test and reference formulation. Safety and tolerability proved to be similarly good with both test and reference formulation. In conclusion, the present trial has demonstrated bioequivalence of the test and the reference formulation, both consisting of fluoxetine hydrochloride dispersible tablets.

Pharmacokinetics and pharmacodynamics of safinamide, a neuroprotectant with antiparkinsonian and anticonvulsant activity.

OBJECTIVE: This paper describes the pharmacokinetics and the pharmacodynamics, in terms of monoamino oxidase type B (MAO-B) inhibition, in male healthy volunteers of orally administered safinamide, a new neuroprotectant that in experimental models has demonstrated strong anticonvulsant and antiparkinson activities. METHODS: Four clinical trials covering the dose range of 25-10,000 microg/kg were carried out to describe pharmacokinetics, pharmacodynamics and tolerability of safinamide, administered in single or repeated dose regimen to steady state, including a food interaction trial. All the above trials were carried out after the Ethics Committee's approval and signature of the consent form by the volunteers. In single dose trials blood sampling covered a 24 h-period in pharmacodynamic trials, 48 h-period in pharmacokinetic trials. In the case of repeated dose regimen to steady state a pre-dose sample was drawn on the first six study days, whereas the curve was explored on the 7th study day, prolonging blood sampling over a 48 h-period after the last dosing. Safinamide level was determined in plasma by a very sensitive and specific LC-MS-MS method, with a low limit of quantification of 0.5 ng/ml of plasma. Pharmacokinetic analysis was carried out with non-compartmental method and, in one case, also with the two-compartmental method. Monoamine oxidase activity of both types A and B (MAO-A and MAO-B) was determined in plasma at different times (MAO-B) and correlated to safinamide levels, or in urine (MAO-A). RESULTS: Pharmacokinetics of safinamide proved to be linearly and proportionally related to the administered doses. The absorption of safinamide was rapid with peak plasma concentrations ranging from 2 to 4 h. Food prolonged the rate and did not affect the extent of absorption of safinamide. In repeat dose regimen once daily, the steady state was reached on the 5th study day with a marginal accumulation factor of 1.5-1.7. The drug was cleared with a t(1/2) of about 22 h. Safinamide reversibly inhibited MAO-B enzyme. Full inhibition was observed with single doses >/= 600 microg/kg, and a relevant, dose dependent, progressive inhibition was encountered with doses starting from 25 microg/kg. Even at the highest single dose of 10 mg/kg no evidence of MAO-A inhibition was observed. CONCLUSION: Enteral absorption of the drug is linear and proportional to the doses administered. The drug is cleared from the body with a t(1/2) of approximately equal to 22 h, without producing any clinically relevant accumulation at steady state. The MAO-B inhibitory activity, without affecting MAO-A, is useful to prevent a dopamine bioinactivation in patients suffering from Parkinson's disease. Safinamide tolerability in the four clinical trials proved to be good.

Bioequivalence of ticlopidine hydrochloride administered in single dose to healthy volunteers.

Ticlopidine hydrochloride (CAS 55142-85-3) is an inhibitor of platelet aggregation used in the management and prevention of thromboembolic disorders.A new formulation of ticlopidine hydrochloride (test) was compared to the reference Tiklid, present in the market, in order to assess their bioequivalence and to register the new formulation as a generic according to the Abbreviated New Drug Application (ANDA) procedure.Twenty-four healthy male volunteers were treated with the two formulations (one tablet containing 250mg of active ingredient) according to a single-dose, balanced, crossover, double-blind design with a washout between the two study periods. Plasma concentration of ticlopidine was assayed in timed samples over a 24h-period with a well-validated HPLC method with UV detection, which allowed 5ngml(-1) to be assayed as the lowest quantifiable concentration. The double-blind key was disclosed only after having completed the assay of unknown samples. From plasma concentrations, C(max), t(max), AUC(0-t), AUC(0- infinity ) and t(1/2) were evaluated through non-compartmental pharmacokinetic analysis. C(max) and AUCs were log(10)- transformed and statistically processed using crossover ANOVA. No statistically significant formulation, period, or sequence effect was encountered. Ninety percent confidence intervals of C(max) and AUCs were comprised in the stipulated 0.80-1.25 range. Similarly, Schuirmann's test led to statistically significant degrees on both the sides explored. Time to peak, t(max), processed with the non-parametric Kruskal-Wallis' test, did not show any statistically significant degree. According to guidelines operating in Europe, the test formulation of ticlopidine hydrochloride can be declared bioequivalent with the reference, both formulations in 250mg tablets.

Pharmacokinetic and pharmacodynamic comparative study of zofenopril and enalapril in healthy volunteers.

Zofenopril calcium (CAS 81938-43-4) is a new angiotensin converting enzyme (ACE) inhibitor, which in addition to the typical activity of the class, proved to possess a specific cardioprotective effect due also to the presence of the sulfhydryl group. In this trial zofenopril calcium and enalapril maleate (CAS 76095-16-4) were given to 20 healthy volunteers of both sexes in repeated dose regiment at two dose levels: 30 mg and 60 mg zofenopril calcium and 10 mg and 20 mg enalapril maleate. The study was conducted according to a two-period, two-sequence, crossover design, with washout. ACE activity in serum and zofenopril, zofenoprilat, enalapril and enalaprilat plasma concentrations were determined during and on the last day of the two study periods. Both zofenopril and enalapril were extensively converted through hydrolysis to their active metabolites zofenoprilat and enalaprilat, respectively. Zofenopril exhibited a complete and a more rapid hydrolysis rate compared to enalapril, which is reflected by the higher metabolite to parent drug ratio of Cmax and AUCss, tau showed by this compound. Even though only two dose levels were investigated in this trial, the pharmacokinetics of both drugs seem to be linear. In line with previous trials, both compounds at both dose levels investigated produced complete or almost complete inhibition of ACE activity in serum, for a period lasting 6-8 h after administration, the inhibition being still relevant 24 h thereafter. The tolerability of the two drugs at both dose levels proved to be very good as demonstrated by subjective and objective symptoms, by the absence of relevant adverse events, and by laboratory biochemical parameters and vital signs evaluated before and after the trial. Blood pressure showed a fairly decreasing trend with both the drugs, systolic and diastolic blood pressure values being however within normal range in all the subjects. In no case symptoms of hypotension were experienced. In conclusion, zofenopril calcium and enalapril maleate show very good tolerability and appear to exert similar activity on serum ACE. The main difference in the pharmacokinetics of the two compounds is the conversion from pro-drug to the active metabolite which is faster with zofenopril.