This is why Darvon & Darvocet are such dangerous and fatal drugs

Pharmacokinetics and pharmacodynamics of Dextropropoxyphene (DXP)

DXP is rapidly absorbed after oral administration and the peak plasma levels are usually attained within one hour of a single dose. However, since DXP undergoes marked first-pass biotransformation, only a small proportion of the absorbed dose enters the circulation in unchanged form. The remainder of the drug is metabolized by intestinal and hepatic enzymes during absorption, under-going demethylation to norpropoxyphene.

Hence, following repeated administration of DXP the norpropoxyphene plasma concentration rises, and it is eliminated more slowly than the parent drug, the plasma concentration of norpropoxyphene becomes considerable higher than of DXP. (Wolen et al., 1971, Wagner et al., 1972, McMahon et al., 1974, Verebely and Inturrisi, 1974, Welling et al., 1976, Musa and Lyons, 1976, Gram et al., 1979, Gibson et al., 1980, Inturrisi et al., 1982, Young 1983, Lawsson and Northrigde, 1987.)

It has been found to alcohol reduces the first-pass biotransformation of DXP, so that the availability of the administered dose may enhanced by 25-50% (Oguma and Levy, 1981, Girre et al., 1991.)

If the whole reference list is desired, please notify me

Excerpts from “Studies on Dextropropoxyphene With Special Reference to Dependence Among Chronic Pain Patients, Classification of the Manner of Death in Fatal Poisonings, and Characteristics of the Fatal Poisoning Victims” by Birgitta Jonasson. Acta Universitatis Upsalienses, Uppsala 2000.

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