Pharmacokinetics of alpha-dihydroergocriptine in rats after single intravenous and single and repeated oral administrations.

The pharmacokinetics of alpha-dihydroergocriptine methane sulphonate in rats were investigated using an HPLC method for the detection of unchanged alpha-dihydroergocriptine (DHEK) in plasma, organs (kidneys, heart, lungs, spleen, liver, and brain), and urine. The plasma profile of DHEK obtained after intravenous administration at a dose of 5 mg kg-1 (as base) of DHEK methane sulphonate showed a three compartment pharmacokinetic model with an elimination half-life of 6.78 h. The kinetics of DHEK after a single oral administration at a dose of 20 mg kg-1 (as base) showed two peaks: the second peak, at about 6 h, was probably due to an enterohepatic cycle. The disposition of DHEK consisted of an absorption half-life of 0.02 h, a distribution half-life of 2.15 h and an elimination half-life of 5.83 h. The pharmacokinetics of DHEK, after repeated oral administrations at the same dose, were similar to those after a single oral administration. The absolute bioavailability was 4.14% after a single oral administration and 3.95% after repeated oral administrations. The analysis of the organs showed that DHEK was rapidly absorbed and distributed in all tissues, mostly in lungs, kidneys, and liver, but it is interesting to observe that it also reached the brain. After repeated oral administrations plasma and tissue concentrations were similar to those obtained after a single administration; therefore it is possible to exclude the onset of autoinduction or accumulation phenomena of DHEK in rats' organs. Urinary excretion of the unchanged drug was low (0.38% of the administered dose in the intravenous route and 0.04% in the oral route), being in agreement with a low oral bioavailability and a rapid and extensive metabolism (first-pass effect).

Pharmacokinetics of pidotimod in rats and dogs.

The pharmacokinetic studies on pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) a new biological response modifier, following intravenous, intramuscular or oral administrations in rats and dogs are reported in this paper. Plasma, urine and organ concentrations were determined by HPLC. Analytical methods were validated for specificity, sensitivity, recovery, accuracy and reproducibility; recovery was very close to 100%, the coefficients of variation of accuracy and reproducibility showed low values. In the rat the pharmacokinetic parameters obtained after oral administration demonstrate that pidotimod is a very fast absorbed, distributed and eliminated drug (t1/2el = 1 h) and that it shows high total clearance and distribution volume. Bioavailability was 100% in the intramuscular route and 27% in the oral route. Pidotimod distributes quickly in the main organs, in particular in kidneys and liver; the time course of the levels in organs follows that of plasma levels after intramuscular administration. After repeated intramuscular administrations no phenomena of accumulation or autoinduction were evident. The urinary excretion of the unmodified drug is 75.6% after intravenous and 31.1% after oral administration. The behaviour of pidotimod in dog after oral administration is quite similar to that observed in rat, with a t1/2el of 1.47 h, absolute bioavailability of 37%, high total clearance and distribution volume. Also in the dog the repeated intravenous and oral administrations do not cause any accumulation or autoinduction phenomena.

Pharmacokinetics and oral bioavailability of pidotimod in humans.

Pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6), a new biological response modifier, was investigated in 3 different pharmacokinetic experiments in healthy volunteers. A first trial was carried out with a cross-over design in 12 subjects, given the drug in single administration by intravenous route (200 mg in bolus) and by oral route at 3 dose levels: 200, 400 and 800 mg (tablets). The second experiment was performed in 36 subjects, by intramuscular route at 50, 100 and 200 mg (12 volunteers/group) twice a day for 15 days. Blood samples were drawn and urine collected at different times after the first and the last administration (29th) of the compound. The third experiment was done in 12 subjects given the product at the same single oral dose (800 mg) in different galenic formulations: sachets, vials and tablets, to assess the relative bioavailability, with a cross-over design. Pidotimod plasma and urinary levels were measured by HPLC. The plasma levels after parenteral administration followed a second-order pharmacokinetic, while after oral administration they were processed by a first order input-output model.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of pidotimod in elderly volunteers and in renal failure patients.

The pharmacokinetics of pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) in elderly volunteers and in patients with renal failures were investigated. No differences in absorption, excretion and pharmacokinetic parameters was evident between old volunteers and the youngs of a previous work. Patients with impaired renal function showed different pharmacokinetic parameters of pidotimod in relation to different grade of kidney function. There were linear relationships between elimination half-lives and plasma levels of creatinine and urea; longer half-lives correspond to higher levels of creatinine and urea. As the half-life of the compound did never exceed 8-9 h, the data do not support any change of pidotimod administration schedule (every 24-12 h).

Pharmacokinetics of ciclopirox olamine after vaginal application to rabbits and patients.

The authors reported the plasma levels and pharmacokinetic parameters of ciclopirox olamine in rabbits after i.v. and intravaginal administrations and in female patients after vaginal administration. Plasma levels of total and free ciclopirox were determined by a HPLC method. In rabbit ciclopirox showed a half-life of 2.22 h and an intravaginal bioavailability of about 2%. In female patients ciclopirox showed low intravaginal absorption; this value might explain the good local and systemic tolerability and also the penetration of drug in deep tissue.

A new HPLC method for pidotimod plasma levels determination.

This paper describes a HPLC method for the determination of Pidotimod (3-L-pyroglutamyl-L-thiazolidine-4-carboxylic acid; PGT/1A), a new biological response modifier, in plasma. The column was an Aminex Ion Exclusion HPX 874 with a PRP precolumn, the mobile phase was 0.05% sulfuric acid-acetonitrile (88:12, v/v), the flow rate was 0.6 ml/min, the detection wavelength was 210 nm. Plasma (1 ml) was added with internal standard (Oxiracetam, concentration 400 micrograms/ml) (50 microliters) and 35% perchloric acid (100 microliters). The supernatant (0.5 ml) was added with mobile phase (0.5 ml) and, after centrifugation, injected into the column. The retention times of Pidotimod and Oxiracetam were 16.5 and 13.8 min. respectively. The method was validated for recovery, accuracy and reproducibility. The results after oral administration of 800 mg of Pidotimod in male volunteers were also given. This method is better than that previously described because it utilizes an internal standard and reaches a lower detection limit.

HPLC method for pharmacokinetic studies on ciclopirox olamine in rabbits after intravenous and intravaginal administrations.

This paper reports a HPLC method to detect unchanged and glucuronide derivatives of ciclopirox olamine (a substituted 2-pyridone antimycotic) and gives pharmacokinetics in rabbits after i.v. and intravaginal administration. The HPLC method utilizes a RP 18 reverse phase column, a mobile phase of water and acetonitrile (60/40), a flux of 1 ml/min and wavelength of 304 nm. For the determination of free ciclopirox the plasma drug is methylated with dimethyl sulphate, extracted with n-exane, purified on Adsorbex CN and injected into the column. For the determination of total (free and glucuronide derivatives) ciclopirox the plasma is previously hydrolized with beta-glucuronidase before the application of the above procedure. In rabbits the drug is administered at 15 mg/kg for both routes; the t1/2 elim is 2.1 hours, the total clearance/F is 0.73 1.h-1 and the distribution volume/F is 2.2 1. Ciclopirox olamine, after intravaginal administration, shows low absorption (about 2%) and is mainly transformed into glucuronide derivatives.

High-performance liquid chromatographic determination of cephacetrile.

A rapid and accurate quantitative determination of cephacetrile in finished bulk and dosage forms is reported. The high-performance liquid chromatographic method is free of interference by acetyl hydrolysis products and synthesis by-products. The assay can be performed in about 15 min, affording less than 0.7% coefficients of variation within and between days. The chromatographic results are in good agreement with the microbiological assay requested by the "Code of Federal Regulations" for certification of cephacetrile sodium.

GLC determination of 6-aminopenicillanic acid and 7-amino-3-methyl-delta3-cephem-4-carboxylic acid.

A quantitative GLC determination of 6-aminopenicillanic acid and 7-amino-3-methyl-delta3-cephem-4-carboxylic acid is presented. The results obtained are in good agreement with those of known chemical procedures. The method is free from interference by related substances.