Papaverine (Latin papaver, "poppy") is an opium alkaloid antispasmodic drug, used primarily in the treatment of visceral spasms and vasospasms (especially those involving the intestines, heart, or brain), occasionally in the treatment of erectile dysfunction and acute mesenteric ischemia. While it is found in the opium poppy, papaverine differs in both structure and pharmacological action from the analgesic morphine and its derivatives (such as codeine). History Papaverine was discovered in 1848 by Georg Merck (1825–1873). Merck was a student of the German chemists Justus von Liebig and August Hofmann, and he was the son of Emanuel Merck (1794–1855), founder of the Merck corporation, a major German chemical and pharmaceutical company. Uses Papaverine is approved to treat spasms of the gastrointestinal tract, bile ducts and ureter and for use as a cerebral and coronary vasodilator in subarachnoid hemorrhage (combined with balloon angioplasty) and coronary artery bypass surgery. Papaverine may also be used as a smooth muscle relaxant in microsurgery where it is applied directly to blood vessels. Papaverine is used as an erectile dysfunction drug, alone or sometimes in combination. Papaverine, when injected in penile tissue, causes direct smooth muscle relaxation and consequent filling of the corpus cavernosum with blood resulting in erection. A topical gel is also available for ED treatment. It is also commonly used in cryopreservation of blood vessels along with the other glycosaminoglycans and protein suspensions. Functions as a vasodilator during cryopreservation when used in conjunction with verapamil, phentolamine, nifedipine, tolazoline or nitroprusside. Papaverine is also being investigated as a topical growth factor in tissue expansion with some success. Papaverine is used as an off-label prophylaxis (preventative) of migraine headaches. It is not a first line drug such as a few beta blockers, calcium channel blockers, tricyclic antidepressants, and some anticonvulsants such as divalproex, but rather when these first line drugs and secondary drugs such as SSRIs, angiotensin II receptor antagonists, etc. fail in the prophylaxis of migraines, have intolerable side effects or are contraindicated. Papaverine is also present in combinations of opium alkaloid salts such as papaveretum (Omnopon, Pantopon) and others, along with morphine, codeine, and in some cases noscapine and others in a percentage similar to that in opium, or modified for a given application. Papaverine is found as a contaminant in some heroin and can be used by forensic laboratories in heroin profiling to identify its source. The metabolites can also be found in