Papaverine dosage

Undesirably prolonged erections (duration of 5 and 6 hours) occurred in 2 patients who had been given 5 or 10 mg of diazepam intravenously for anxiety before a 60-mg intracavemosal injection of papaverine. Papaverine acts by relaxing the arterioles that supply the corpora so that the pressure rises. The increased pressure in the corpora compresses the trabecular venules so that the pressure continues to maintain the erection. Diazepam also relaxes smooth muscle and it would seem that this can be additive with the effects of papaverine. The authors of the report say that caution should be exercised in the choice of papaverine dosage in patients taking anxiolytics (i.e. use less) although tiiese two cases involving diazepam seem to be the only ones recorded. ... 

The alkaloids papaverine and theophylline are listed as inhibitors, but not strychnine. However, many or most alkaloids should be suspect, depending on the dosage level. 

Papaverine Hydrochloride. The Evaluation of Two New Dosage Forms Int. J. Clin. Pharmacol. Biochem. 15 (5) 230-233 (1977) CA 87 106698v... 

The pharmacological effects of this complex mixture of alkaloids in opium may, in some respects, be more beneficial than the effects of an individual alkaloid. The effect of opium in the treatment of diarrhoea is better than that of either morphine or codeine given individually. It is possible to calm the gastrointestinal tract with a dose which contains only half of the dose which would be necessary for morphine alone. The combination of the increase in stretch reflex caused by morphine and the inhibition of increased peristaltic action by papaverine leads to a better therapeutic effect. The increase in muscle tone due to morphine is reduced by papaverine, and other benzylisoquinolines also participate in this tranquillisation of the g.i. tract. In the normal 50 mg dosage of opium used for the treatment of diarrhoea there is about 5 mg of morphine, 0.5 mg of papaverine and 3 mg of nos-capine which contrasts markedly with a dose of 100—200 mg of papaverine if this were given alone. The analgaesic activity of opium is due mainly to the morphine present, as the levels of codeine, neopine and papaverine are relatively small. The respiratory depression effect of opium is also due to the morphine content and the antagonistic effects of noscapine and narcotoline are not so pronounced. Thus the main use of opium in medicine is for the treatment of diarrhoea. 

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