Pharmacokinetics and dosage adjustment of cefotiam in renal impaired patients

The pharmacokinetics of cefotiam were investigated after intravenous administration of 1 g to 2 healthy volunteers with normal renal function and to 16 patients whose creatinine clearance ranged from 4.7 to 0.1 l/h (78 to 1.66 ml/min). The elimination half-life varied from 1.1 h in normal subjects to 13 h in patients and the total plasma clearance from 21 to 0.6 l/h (350 to 10 ml/min). The urinary recovery decreased from 62% of the dose in normal subjects to 1.1% in patients, and the renal clearance from 15 to 0.01 l/h (250 to 0.5 ml/min). Plasma and renal clearances of cefotiam correlated well with the creatinine clearance. The dosage schedule for cefotiam in patients with normal renal function can be used in the presence of renal failure when the creatinine clearance is equal to or greater than 1 l/h (16.6 ml/min). For patients whose creatinine clearance is less than 1 l/h, the dose must be decreased to 75% of that for a patient with normal renal function only when it is given every 6 or 8 h.

Comparative pharmacokinetic profiles of metoprolol and chlorthalidone administered alone or in combination to healthy volunteers

A potential pharmacokinetic interaction between the beta-blocking drug, metoprolol, and the diuretic, chlorthalidone, has been investigated in three single or multiple dose studies in healthy volunteers. The pharmacokinetic profile of metoprolol 100 mg was not affected by pretreatment with or co-administration of chlorthalidone 25 mg twice daily. Similarly, the pre-dosing steady-state level of chlorthalidone during chronic treatment and its blood level profile after a single 25 mg dose were not affected by metoprolol. The bioavailabilities of the 2 drugs administered in combination were identical to those observed when each drug was administered alone. These studies demonstrate that there is no pharmacokinetic interaction between metoprolol and chlorthalidone when doses of 100 and 25 mg, respectively, are co-administered twice daily.

Measurement of clomipramine, N-desmethyl-clomipramine, imipramine, and dehydroimipramine in biological fluids by selective ion monitoring, and pharmacokinetics of clomipramine

To quantitatively determine tricyclic antidepressant agents, we used a combined gas chromatograph/mass spectrometer system, and deuterium-labeled internal standards. Recovery exceeds 95% and the coefficient of variation is less than 4% for human whole-blood samples supplemented with 5 to 15 ng of clomipramine hydrochloride or 20 to 60 ng of dehydroimipramine hydrogen fumarate per milliliter. For both amines, the detection limit is 0.3 mug/liter; Six healthy volunteers who received a single oral dose of 50 mg of clomipramine hydrochloride showed peak drug concentrations in the blood 3 to 5 h after administration, ranging between 14.4 and 30.1 mug/liter. Plasma/whole blood concentration ratios varied from 0.70 to 1.20, and the cumulative renal elimination from 0 to 72 h is less than 0.2% of the dose. This method is suitable for in vivo bioavailability studies of unchanged clomipramine, dehydroimipramine, and imipramine after a single oral dose of as little as 25 mg.

Measurement of clomipramine, N-desmethyl-clomipramine, imipramine, and dehydroimipramine in biological fluids by selective ion monitoring, and pharmacokinetics of clomipramine

To quantitatively determine tricyclic antidepressant agents, we used a combined gas chromatograph/mass spectrometer system, and deuterium-labeled internal standards. Recovery exceeds 95% and the coefficient of variation is less than 4% for human whole-blood samples supplemented with 5 to 15 ng of clomipramine hydrochloride or 20 to 60 ng of dehydroimipramine hydrogen fumarate per milliliter. For both amines, the detection limit is 0.3 mug/liter; Six healthy volunteers who received a single oral dose of 50 mg of clomipramine hydrochloride showed peak drug concentrations in the blood 3 to 5 h after administration, ranging between 14.4 and 30.1 mug/liter. Plasma/whole blood concentration ratios varied from 0.70 to 1.20, and the cumulative renal elimination from 0 to 72 h is less than 0.2% of the dose. This method is suitable for in vivo bioavailability studies of unchanged clomipramine, dehydroimipramine, and imipramine after a single oral dose of as little as 25 mg.

Biotransformation and pharmacokinetics of sulfinpyrazone (Anturan) in man

The absorption, biotransformation and elimination of sulfinpyrazone, 1,2-diphenyl-3,5-dioxo-4-(2'-phenylsufinylethyl)-pyrazolidine, have been studied by administration of single 200 mg oral doses of a 14C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and complete and the plasma concentration of unchanged drug reached maximum values of 22.67 and 13.04 mug/ml, respectively, after 1 - 2 hours. The elimination half-life in the two subjects, calculated from the decline between 3 and 8 hours, was 2.7 and 2.2 hours. The integrated concentration of unchanged sulfinpyrazone in plasma, estimated from the area under the concentration curves (AUC), was almost as high as that of total 14C-substances, so the proportion of metabolized drug in plasma was low. In no case did the AUC of the three specifically determined metabolites. i.e. the sulphone G 31 442, the "para-hydroxy"=compound G 32 642 and the "4-hydroxy"- compound GP 52 097, exceed 4% of the sulfinpyrazone value. More than 95% of whole blood radioactivity was confined to plasma. The oral dose was rapidly and completely excreted, since within 4 days more than 95% was recovered, 85% from urine and 10% from faeces. A large proportion of the dose was excreted as unchanged drug in the two volunteers: 51 and 54% of total urinary radioactivity was present as sulfinpyrazone; 8.2 and 8.8% was present as "para-hydroxy"-metabolite, 2.7 and 3.0% as sulphone-metabolite, and 0.6 and 0.8% as "4-hydroxy"-metabolite. About 30% of urinary radioactivity consisted of highly polar metabolites. Spectroscopy of them showed that they were the C-beta-glucuronides of sulfinpyrazone (28%) and the corresponding sulfone (2%). In these metabolites the C(4) of the pyrazolidine ring was directly attached to glucuronic acid, and thus they represent a new type of biosynthetic conjugate.

[Anticoagulant efficacy of Sintrom and blood concentration of Ludiomil on simultaneous administration of the two preparations]

As long-term anticoagulant therapy with coumarin derivates like Sintrom becomes more and more important the question arises whether there is an interaction with a new drug like Ludiomil. An open, noncomparative trial was carried out with 20 patients receiving Sintrom (overall mean :3.0 mg/d, range :0 to 10 mg/d) for a period of 4 weeks, and in addition, during the second and third week Ludiomil (50 mg t. i. d.) orally. As a measurement of the efficacy of the antiocoagulant therapy, the correlation coefficients between the doses of Sintrom and the prothrombin value of the nex day were calculated for each patient and each week separately. An analysis of variance did not show any statistically significant difference between the correlation coefficients of the weeks with and without Ludiomil therapy, i.e. there is no change in the efficacy of the anticoagulant therapy. During the Ludiomil therapy the control of the anticoagulant therapy was slightly better, i.e. the fluctuations of the prothrombin values less, but statistically these differences were not significant. The plasma levels of Ludiomil in these patients were similar to thse found previously in both depressed and healthy volunteers.