PLASMA HALF-LIFE, TISSUE DISTRIBUTION, AND EXCRETION OF TRIAMCINOLONE-H³

¹ Experimental Therapeutics Research, Lederle Laboratories Division, American Cyanamid Company, Pearl River, New York

Triamcinolone was rapidly removed from dog blood after intravenous injection at 2 mg/kg; not more than 15% of the dose could be extracted from total plasma 3 minutes after injection. During the period of logarithmic fall in plasma triamcinolone concentration (22 to 480 minutes after injection), the half-life of triamcinolone was 116.7 ± 7.4 minutes; the half-life of hydrocortisone measured by the same procedure was 54.3 ± 3.6 minutes. Triamcinolone exhibited the longest plasma half-life in the dog thus far reported for a corticosteroid.

Triamcinolone-H³ was deposited primarily in the muscle, liver, intestine, skin, and kidney of the rat following intravenous administration. Comparisons with published data which indicate a similar deposition of hydrocortisone did not contribute to an understanding of the enhanced biological activity of triamcinolone.

Excretion of radioactivity by the dog was divided equally between urine and feces; a total of 85 to 90% of injected tritium was recovered up to 120 hours after dosage. Approximately 20% of injected triamcinolone-H³ was recovered unchanged in dog urine after injection at 2 mg/kg. Comparisons of in vitro metabolism, plasma half-life, and excretion of triamcinolone and other corticosteroids led to the suggestion that the enhanced biological activities of certain substituted corticosteroids are a direct result of their increased concentrations at the sites of activity.