Papaverine

Papaverine is one of the alkaloids found in the opium poppy.  It is described as a ‘feeble central analgesic’ but it has no addictive or habit forming qualities. 

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, 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!!

It has no record of hallucinatory experience via the eHealthme web site.

Uses

It is used medicinally in cases of spasm  - visceral spasm, vasospasm (especially those involving the heart and the brain), bronchial spasm, ‘biliary colic’ and so on.  It used to be used for eclampsia, an acute and life-threatening complication of pregnancy, characterised by the appearance of seizures.  It is also used occasionally in the treatment of erectile dysfunction.  The penis is normally kept in place in its limp state by contraction of the muscles.  When the muscles relax you get an erection, so a muscle relaxant helps with ‘impotence’ – willy failure.  The following quote says it all, it is magical.

“I don't know if it's still used in these days of Viagra, Cialis, et al but once upon a time a preparation containing Papaverine was used in impotence treatment - it was (wince) directly injected into the penis just before sex ( there's a real mood maker if ever there was one - 'just hang on there honey. while I stick a spike in the old fella' there's just got to be a prick joke or two in there somewhere) whereupon it caused an almost instantaneous erection, woo hoo! chocks away, ginger! it makes my eyes water just to think about it! of all the places I've ever stuck a needle, THERE is somewhere I could not go!”

These days it is available as a topical gel! 

Papaverine is also used today as a smooth muscle relaxant in microsurgery, as a second line drug for convulsions in general, and occasionally for migraine.  And it has found use in plastic surgery as a cream that can be used to expand the skin and make it less tight.

Despite all the uses to which it has been put, the Peripheral and Central Nervous System Drugs Advisory Committee of the FDA in the USA  concluded after studies and hearings that Papaverine “has not been shown to be effective for its claimed indications. These include use as a smooth muscle relaxant in the treatment of cerebral and peripheral ischemia associated with arterial spasm and myocardial ischemia complicated by arrhythmias; and for visceral spasm as in ureteral colic, biliary colic, or gastrointestinal colic”.  So there you go.

The Receptors   - PDE10A

Phosphodiesterase 10A (PDE10A) is a recently identified endogenous chemical found in the brain.  Papaverine is a potent, specific inhibitor of PDE10A. 

PDE10A is an enzyme that reduces some of the signalling that goes on in the brain.  This in itself is a bit meaningless unless we know what the signals are for, but perhaps of more importance from our point of view,  Papaverine can inhibit

• ‘conditioned avoidance responding’ in rats and mice – so learned behavior where the  antecedent action and its consequence are used to influence the behaviour.  In effect Papaverine knocks some of the reasoning function out
• and ‘amphetamine-stimulated locomotor activity’ in rats – so a slowing down of physical activity

The receptors – adenosine

Papaverine inhibits adenoside reuptake, in effect it prolongs the effects of any endogenous chemicals or ligands on these receptors or maximises the effects of any chemicals there happen to be. Although it is not an agonist it will appear to be one.   The primary target for papaverine is the endogenous [in our body naturally ] adenosine.  

Receptors – adrenoceptors

 Papaverine “acts as an antagonist against noradrenaline in a non-competitive fashion”. It is a weak antagonist of noradrenaline.  “the antagonistic activity against noradrenaline was about 1000-times weaker,  D 600 as well as nifedipine were about equipotent with papaverine”.  But it is through this receptor that papaverine is able to provide its anti convulsant activity, its ability to ‘cure’ erectile dysfunction and any number of the other effects it exhibits on the smooth muscle.  See Adrenaline and its ligands.  There are five main adrenoceptors receptors.  Papaverine appears to act on all of them including the fifth.  So papaverine will counteract the effects  in an antagonistic way. Its overall effects thus being:

• Relax the  smooth muscle contraction of the bladder  - we will wee more and in cases where weeing is hard such as when you have prostrate problems, it may help men to wee.    
• Relax the smooth muscle contraction of the penis, we will have an erection
• Relax the smooth muscle of the gut helping with ‘biliary colic’
• Relax the veins  - causing vasodilation
• Relax  the smooth muscle contraction of the heart, this may cause heart arrhythmias
• Relax stomach muscles and reduce spasms there
• Relax the muscles in the intestine and colon as well as the duodenum as well as the rectum enabling us to go to the loo – thus a remedy against constipation
• Relax the clitoris muscles aiding female orgasm
• Relax  the smooth muscle contraction of the lungs and help with bronchial spasm - coughs