the urine of heroin users, allowing street heroin to be distinguished from pharmaceutical diacetylmorphine. Mechanism The in vivo mechanism of action is not entirely clear, but an inhibition of the enzyme phosphodiesterase causing elevation of cyclic AMP and cyclic GMP levels is significant. It may also alter mitochondrial respiration. Papaverine has also been demonstrated to be a selective phosphodiesterase inhibitor for the PDE10A subtype found mainly in the striatum of the brain. When administered chronically to mice, it produced motor and cognitive deficits and increased anxiety, but conversely may produce an antipsychotic effect, although not all studies support this view. Side effects Frequent side effects of papaverine treatment include polymorphic ventricular tachycardia, constipation, interference with sulphobromophthalein retention test (used to determine hepatic function), increased transaminase levels, increased alkaline phosphatase levels, somnolence, and vertigo. Rare side effects include flushing of the face, hyperhidrosis (excessive sweating), cutaneous eruption, arterial hypotension, tachycardia, loss of appetite, jaundice, eosinophilia, thrombopenia, mixed hepatitis, headache, allergic reaction, chronic active hepatitis, and paradoxical aggravation of cerebral vasospasm. Papaverine in the plant Sauropus androgynus is linked to bronchiolitis obliterans. Formulations and trade names Papaverine is available as a conjugate of hydrochloride, codecarboxylate, adenylate, and teprosylate. It was also once available as a salt of hydrobromide, camsylate, cromesilate, nicotinate, and phenylglycolate. The hydrochloride salt is available for intramuscular, intravenous, rectal and oral administration. The teprosylate is available in intravenous, intramuscular, and orally administered formulations. The codecarboxylate is available in oral form, only, as is the adenylate. The codecarboxylate is sold under the name Albatran, the adenylate as Dicertan, and the hydrochloride salt is sold variously as Artegodan (Germany), Cardioverina (countries outside Europe and the United States), Dispamil (countries outside Europe and the United States), Opdensit (Germany), Panergon (Germany), Paverina Houde (Italy, Belgium), Pavacap (United States), Pavadyl (United States), Papaverine (Israel), Papaverin-Hamelin (Germany), Paveron (Germany), Spasmo-Nit (Germany), Cardiospan, Papaversan, Cepaverin, Cerespan, Drapavel, Forpaven, Papalease, Pavatest, Paverolan, Therapav (Canada), Vasospan, Cerebid, Delapav, Dilaves, Durapav, Dynovas, Optenyl, Pameion, Papacon, Pavabid, Pavacen, Pavakey, Pavased, Pavnell, Alapav, Myobid, Vasal, Pamelon, Pavadel, Pavagen, Ro-Papav, Vaso-Pav, Papanerin-hcl, Qua bid, Papital T.R., Paptial T.R., Pap-Kaps-150. In Hungary, papaverine and homatropine methylbromide are used in mild drugs that help "flush" the bile. References Antispasmodics Bitter compounds Benzylisoquinoline alkaloids Natural opium alkaloids Catechol ethers Phosphodiesterase inhibitors Vasodilators