Pharmacokinetics and therapeutic efficacy of rimantadine in horses experimentally infected with influenza virus A2

William A. Rees, J. Daniel Harkins, Ming Lu, Robert E. Holland, Andreas E. Lehner, Thomas Tobin, Thomas M. Chambers

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Objective - To determine pharmacokinetics of single and multiple doses of rimantadine hydrochloride in horses and to evaluate prophylactic efficacy of rimantadine in influenza virus-infected horses. Animals - 5 clinically normal horses and 8 horses seronegative to influenza A. Procedure - Horses were given rimantadine (7 mg/kg of body weight, IV, once; 15 mg/kg, PO, once; 30 mg/kg, PO once; and 30 mg/kg, PO, q 12 h for 4 days) to determine disposition kinetics. Efficacy in induced infections was determined in horses seronegative to influenza virus A2. Rimantadine was administered (30 mg/kg, PO, q 12 h for 7 days) beginning 12 hours before challenge-exposure to the virus. Results - Estimated mean peak plasma concentration of rimantadine after IV administration was 2.0 μg/ml, volume was distribution (mean ± SD) at steady-state (Vd(ss)) was 7.1 ± 1.7 L/kg, plasma clearance after IV administration was 51 ± 7 ml/min/kg, and β-phase half-life was 2.0 ± 0.4 hours. Oral administration of 15 mg of rimantadine/kg yielded peak plasma concentrations of < 05 ng/ml after 3 hours; a single oral administration of 30 mg/kg yielded mean peak plasma concentrations of 500 ng/ml with mean biovailability (F) of 25%, β-phase half-life of 2.2 ± 0.3 hours, and clearance of 340 ± 255 ml/min/kg. Multiple doses of rimantadine provided steady-state concentrations in plasma with peak and through concentrations (mean ± SEM) of 811 ± 97 and 161 ± 12 ng/ml, respectively. Rimantadine used prophylactically for induced influenza virus A2 infection was associated with significant decreases in rectal temperature and lung sounds. Conclusions and Clinical Relevance - Oral administration of rimantadine to horses can safely ameliorate clinical signs of influenza virus infection.

Original languageEnglish
Pages (from-to)888-894
Number of pages7
JournalAmerican Journal of Veterinary Research
Issue number7
StatePublished - Jul 1999

ASJC Scopus subject areas

  • General Veterinary


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