EFFECT OF PROPOXYPHENE L ON PLASMA-LEVELS AND ANALGESIC ACTIVITY OF D-PROPOXYPHENE IN RAT

  • 1 January 1976
    • journal article
    • research article
    • Vol. 199  (2) , 415-422
Abstract
Oral administration of l-propoxyphene with d-propoxyphene enhances the analgesic activity of d-propoxyphene as expressed in the rat tail heat test. The combination of d- and l-propoxyphene at a dose of 10 mg/kg each had activity in the analgesic assay equivalent to that observed with d-prropoxyphene at a dose of 20 mg/kg. In the same test, l-propoxyphene at a dose of 40 mg/kg had no activity. Co-administration of equal amounts of l-propoxyphene with d-propoxyphene (10 mg/kg orally) increases the circulating plasma levels of d-propoxyphene from 9 .+-. 2 to 114 .+-. 39 ng/ml 15 min after administration. The increase in plasma levels is accompanied by a proportional increase in the brain and lung levels with no significant change in the liver levels. When d-propoxyphene (4 .mu.g/ml) was infused in the isolated perfused rat liver, over 98% of the drug was extracted in a single pass through the liver. When l-propoxyphene was added to the perfusate (4 .mu.g/ml), the extraction of d-propoxyphene was decreased to less than 90%. l-Propoxyphene increases the systemic availability of d-propoxyphene by altering the amount of d-propoxyphene extracted by the liver.

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