Metabolism of MK-499, a class III antiarrhythmic agent, in rats and dogs.

Abstract

MK-499 [(+)-N-[1'-(6-cyano-1, 2, 3, 4-tetrahydro-2(R)-naphthalenyl)-3, 4-dihydro-4(R)-hydroxyspiro(2H-1-benzopyran-2, 4'-piperidin)-6-yl]methanesulfonamide] monohydrochloride is an investigational class III antiarrhythmic agent for treatment of malignant ventricular tachyarrhythmias. The disposition of [3H]MK-499 and [14C]MK-499 was studied in rats and dogs after oral and iv administration. MK-499 was concentrated in organs of excretion and the heart. In the rat, urinary radioactivity elimination values after iv (0.5 mg/kg) and oral (6.25 mg/kg) doses were 21 +/- 3% and 10 +/- 2%, respectively. Corresponding fecal recoveries were 68 +/- 6% and 78 +/- 7%. Similar results were found after corresponding doses of [14C]MK-499. In dogs, urine and feces accounted for 16 +/- 3% and 75 +/- 4% of recovered radioactivity after a [3H]MK-499 iv dose (0.1 mg/kg). Corresponding recoveries after an oral dose (1 mg/kg) were 12 +/- 2% and 76 +/- 3%. Biliary (0-24 hr) excretion accounted for 39 +/- 5% and 41 +/- 18% of [3H] and [14C] oral doses in rats, respectively. Dogs excreted 34% of [3H] oral dose in (0-24 hr) bile. The data indicated that a substantial amount of MK-499 was absorbed by rats and dogs. MK-499, metabolite I (formed by loss of N-substitution), and metabolite II (an acid formed by metabolic scission across the benzopyran ring) each represented 30% of rat urinary label. Rat bile contained MK-499 (10%), II (20%), and IV (10%), which was formed by carbon-4 hydroxylation of the tetralin ring. Additionally, rat bile included glutathione (V) and N-acetyl-1-cysteine (VI) conjugates of a ring-opened metabolite. Metabolite III, a positional isomer of IV, was excreted in rat urine. The major labeled species excreted in dog bile were unchanged MK-499 and its glucuronide (VII), which, respectively, represented 50% and 30% of the biliary radioactivity. MK-499 and a small amount of I represented dog urinary radioactivity. The bioavailability of MK-499 was high in dogs (100%) but low in rats (17%). This difference was probably due to the more extensive presystemic metabolism of MK-499 in rats.

• Authors: S Vickers, C A Duncan, D E Slaughter, B H Arison, T Greber, T V Olah, K P Vyas
• Journal: Drug metabolism and disposition: the biological fate of chemicals (Drug Metab Dispos) Vol. 26 Issue 5 Pg. 388-95 (May 1998) ISSN: 0090-9556 [Print] United States
• PMID: 9571219 (Publication Type: Journal Article)

Chemical References

• Anti-Arrhythmia Agents
• Benzopyrans
• Piperidines
• L 706000

Topics

• Animals
• Anti-Arrhythmia Agents (pharmacokinetics, therapeutic use)
• Benzopyrans (pharmacokinetics, therapeutic use)
• Biological Availability
• Chromatography, High Pressure Liquid
• Dogs
• Dose-Response Relationship, Drug
• Magnetic Resonance Spectroscopy
• Male
• Metabolic Clearance Rate
• Piperidines (pharmacokinetics, therapeutic use)
• Rats
• Rats, Sprague-Dawley
• Tachycardia, Ventricular (drug therapy, metabolism)
• Tissue Distribution