Pharmacokinetics of Moxisylyte in Healthy Volunteers after Intravenous and Oral Administration P. COSTA*,F. BRESSOLLE~, M. BROMET-PETIT§, J. MOSSER~, AND B. SARWIN* Received July 17, 1991, from the ‘Servic? dUrologie Andrologie, Centre Hospitalier Universitaire, Nfmes, France, the *Dbpartement de Phannaminbti ue, Facuttb de Pharmacre, Montpellrer, France, the (Db rtement de Pharmacocinbtique, Biosciences, Orlbans, France, and the

*Dbpartement j e Recherche Clinique, Laboratoires Sarget, Mbrignac, G n c e .

Abstract 0 The concentration-time profiles of metabolites of moxisylyte, an alpha-blocking agent, in the plasma and urine of 12 healthy volunteers were investigated after intravenous (iv) and oral (two formulations) administration. The study was conducted with an open, randomized Latin squares design. Plasma and urine levels of moxisylyte and its biotransformation products were assayed by a specific HPLC method with fluorescence detection. Plasma levels declined in a rnonophasic or biphasic pattern depending on the subject. Two metabolites, conjugated desacetylmoxisylyte (DAM) and conjugated monodesmethylated DAM (MDAM), were found in plasmaand urine. Unconjugated DAM was found in plasma only after iv administration. The apparent elimination half-lives of unconjugated DAM, conjugated DAM, and MDAM were 0.86,1.7, and 3 h, respectively. The total amounts of metabolites (expressed as the equivalent of DAM) excreted in the urine were 75% after iv administration and 68 and 69% after oral administration of the two formulations. Oral absorption appeared to be complete for the two treatments. There was no statistical difference between the two oral formulations studied.

Moxisylyte (thymoxamine; 11, is an alpha-blocking drug that actsby competingwith noradrenaline at receptor sites.1.2 This drug has been used since 1965 as a vasodilator in the treatment of various vascular disorders.- Rapid biotransformation is observed after intravenous (iv) and oral administration.@No unchanged compound is found in the body. More than 90% of the metabolism can be ascribed to six metabolites: desacetylmoxisylyte (DAM) (3),monodesmethylated DAM (MDAM) (4), sulfate-conjugate DAM and MDAM, and the glucuronides of DAM and MDAM10-12 (see structure). The metabolites DAM and MDAM and their sulfate conjugates are pharmacologically active.12 With regard to the alpha-blocking effect found in isolated organs, moxisylyte, DAM, and MDAM were nearly equipotent, and the sulfate conjugates of DAM and MDAM showed reduced effectiveness.12 The vasodilating effect observed after the administration of DAM and MDAM and their sulfate conjugates to anesthetized dogs may not be an alpha-blocking action alone but may be an effect of unknown origin.12 There are few references to date concerning the pharmacokinetic profile of moxisylyte. Phase I and I1 studies of this drug were conducted by Nakashima1sJ4 with only a small number (less than five) of healthy volunteers after single iv and multiple oral dosing; the pharmacokinetic profiles of DAM and of the total metabolites of moxisylyte were investigated over a 150-min period with three plasma samples. Information on the biotransformation and pharmacokinetic profile of DAM in humans after iv (one subject) and oral (one subject) administration of 14C-labeleddrug was provided by Vollmer and Poisson.12 In this work, the pharmacokinetic properties of moxisylyte in 12 healthy volunteers following single-dose iv and oral administration were studied; in addition, we provide for the first time the pharmacokinetic profiles of conjugated DAM and MDAM.During this study, the oral absorption of two 0022-3549/92/1200-122?3$02.50/0 (B 1992, American Pharmaceutical Association

Accepted for publication May 28, 1992.

Compound

R1

OH

CHa

OH

H

formulations of moxisylyte (one already marketed nonsectile tablet Uroalpha and a new precoated sectile tablet allowing easier adjustment of the therapy to a patient’s needs) was evaluated.

Experimental Section Drug Products-Moxisylyte, or thymoxamine, 442-dimethylamino-ethoxy)-5-isopropyl-2-methylphenylacetate (1)(used ae the hydrochloride), the internal standard 4-[2-(ethylmethylamino)ethoxyl-2-methyl-54 1-methy1ethyl)phenylacetate(2) (used as the hydrochloride), DAM (3), and MDAM (4) were used for the analytical methods. Moxisylyteampules for iv administration (10 mg/2 mL), moxisylyte precoated sectile tablets (120 mg per tablet), and moxisylyte noneectile tablets (120mg per tablet) were studied during this trial. AU drug products were provided by Laboratories Sarget (Merignac, France). Subjects-The study was conducted with 12 male Caucasian subjects in good health and 22 to 38 years old (mean, 28 2 5 years). They weighed no more than f 15% of the normal weight for height as described in Metropolitan Life Insurance tables. The mean body weight was 74 2 9 kg (56-88kg),and the mean height was 177 2 5 cm (167-186 cm). Each subject underwent a clinical examination before admission to the study. A physical examination revealed no relevant abnormalities. The subjects were free of clinically significant disease, especially renal, hepatic, cardiac, or central nervous system disease.No drug of any kind was permitted in the 2 weeks before the administration of drug formulations or on the test days themselves. In addition, no drugs thought to be enzyme inducers or inhibitors were taken in the 3 months before the study. Subjects who smoked more than 10 cigarettes (four pipes) or the equivalent per day, who had a history of alcoholism or drug abuse, or who consumed more than 50 g of alcohol per day were excluded. The subjects were instructed Journal of Pharmaceutical Sciences I 1223 Vol. 81, No. 12, December 1992

to maintain their usual diet, not to drink any coffee, tea, or caffeinecontaining beverage, and to refrain from hard labor during the 48 h preceding the experiment. Laboratory tests, including hematology (e.g., complete blood count and routine blood chemistries) and urinalysis (routine "stick' tests for glucose and protein and examination for crystals), were done for all subjects before the start of the study and at the end of the study. The subjects were fully informed of the study design and were enrolled in the study after having given written informed consent. The protocol was approved by the local hospital ethics committee. Study Design-Three different forms of moxisylyte were administered to each subject in a three-period, open, randomized Latin squares study with at least a 2-week interval between each administration. Each subject received a short iv infusion (5 min) of moxisylyte (0.5 mgkg) dissolved in sodium chloride (0.75%)to obtain an isotonic drug solution (treatment A), a single precoated sectile 120-mg tablet (treatment B),and a single nonsectile 120-mgtablet (treatment C). Atotal of 200 mL of water was given with each oral administration. The subjects fasted for 12 h before drug administration. They were given a light breakfast (twobiscuits and 20 mL of decaffeinated coffee) as the first meal of the day, 2 h after dosing. Four hours after administration, they were given a standard lunch. During the study, the subjects had free access to fluids, except for alcohol- and caffeine-containing beverages. Sample Collection-Blood samples were drawn into heparinized tubes either by venipuncture or through an indwelling catheter inserted into a n antecubital vein for repeated blood sampling. Moxisylyte was infused over 5 min (electric pump) into a contralateral cubital vein. Samples were collected immediately before and 5, 10, 20, 30,45, 60, and 90 min and 2, 2.5, 3, 3.5, 4, 5, 6, 7,8, 10, and 24 h after each administration. The blood samples were immediately centrifuged (1000 x g for 10 m i d ; the plasma was placed in two glass tubes and immediately frozen (- 18 "C) until analysis. Urine specimens were collected and placed in acetate buffer (0.1M, pH 4.66, 1 mL for 200 mL of urine) just before and at the following intervals after drug administration: 0-6, 6-10, 10-24, and 24-48 h. The voided urine was collected, the total volume was recorded, and a sample (50 mL) was placed in each of two vials and stored frozen (-18 "C) until analysis. Assessment of Tolerance-Arterial blood pressure and heart rate were determined before and after drug administration. Any adverse events spontaneously reported by the subjects were recorded throughout the trial. Assay Method-Moxisylyte concentrations in plasma and urine were assayed with 2 as an internal standard by a selective and sensitive HPLC method with spectrofluorimetric detection.10 The detection was performed at 195 nm for excitation, without an emission filter. The column was packed with reversed-phase odadecyl silane Ultrasphere (particle size, 5 pm; 250 x 4.6 mm inner diameter) (Beckman,Paris, France). The eluant composition was acetonitri1e:water:sodiumheptanesulfonate (320:620:60) solution (6 g in 100 mL of water); 0.01 M potassium dihydrogen phosphate (pH 5) was added to each liter of the eluant. The flow rate was 1 mL/min. A series of extractions was carried out with different solvent systems to extract DAM and MDAM with the highest possible specificity to prevent the risk of interference during the HPLC analysis. In plasma and urine, conjugated DAM and MDAM were assayed after acid hydrolysis; the parent drugs were measured without the hydrolysis step. The extraction procedure was as follows. A 1-mL volume of plasma or urine, 100 ng of internal standard solution, and 1 mL of 2 M hydrochloric acid were placed in a 10-mL glaas tube. The contents were mixed for 30 s and then heated at 120 "C for 1 h. After the mixture was cooled at room temperature (- 1h), the pH was adjusted to 7-8 with -1 mL of 2 M sodium hydroxide. One milliliter of 0.5 M carbonate buffer (pH 10) and 5 mL of dichloromethane were added, and the mixture was shaken for 15 min. After centrifugation at 4 "C, the aqueous phase was discarded, 0.5 mL of 1 M hydrochloric acid and 2 mL of water were added, and the mixture was shaken for 10 min. The aqueous phase was transferred into another glass tube and then washed with 5 mL of diethyl ether by shaking for 15 min. The organic layer was removed after centrifugation, the pH of the aqueous phase was increased to 7-8 with -0.5 mL of 1M sodium hydroxide, and 1mL of 0.5 M carbonate buffer (pH 10) was added. The metabolites of moxisylyte were then extracted twice with 4 mL of cyclohexane. The combined cyclohexane layers 1224 I Journal of Pharmaceutical Sciences Vol. 81, No. 12, December 1992

were evaporated to dryness, the residue was dissolved in 200 pL of the eluant, and 10-100 pL was injected into the column. During the metabolism studies, enzymatic hydrolysis with either the juice of Helix pomatia or pglucuronidase or arylsulfatase did not result in the complete cleavage of the conjugated metabolites. Indeed, 65% of glucuronides are not hydrolyzed by p-glucuronidase from bovine liver; sulfate conjugates a re not hydrolyzed by either sulfatase or H.pomatia juice.16 In our experience, after hydrolysis with the juice of H.pomatia, about 44% of conjugated derivatives are not cleaved.10 Therefore, concentrations of conjugated metabolites DAM and MDAM were determined after complete hydrolysis with hydrochloric acid (2 M, v/v, 1 h at 120 "0. This method was validated by GLP guidelines. The limits of quantification for DAM and MDAM were 25 and 500 n g h L for plasma and urine, respectively. Within-day and between-day variabilities of the method were

Pharmacokinetics of moxisylyte in healthy volunteers after intravenous and oral administration.

The concentration-time profiles of metabolites of moxisylyte, an alpha-blocking agent, in the plasma and urine of 12 healthy volunteers were investiga...
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