Papaverine

Papaverine is a substance from the group of alkaloids and belongs to the class of antispasmodics. The alkaloid is found in the dried milky sap of the opium poppy.But it can also be produced synthetically.

What is papaverine?

Papaverine is a natural substance found in the milky sap of the opium poppy and other related poppy species. Raw opium contains around one percent papaverine. The pure substance papaverine is effective and at the same time does not have the full range of possible side effects. Like the chemical papaverine derivative, papaverine is a cAMP phosphodiesterase inhibitor. It thus acts on numerous sub-forms of the phosphodiesterase family.

Papaverine is mainly used as a vasodilator drug. It belongs to the group of spasmolytics. Spasmolytics are antispasmodic drugs that reduce the tension in the smooth muscles and relieve their cramps.

The first complete synthesis of papaverine was carried out in 1909 by the researchers Pictet and Gams. The Austrian Guido Goldschmiedt succeeded in dissolving the entire structure a few years later. Papaverine hydrochloride is used pharmaceutically today as a single preparation or in combination preparations.

Pharmacological effect

Papaverine is a cAMP phosphodiesterase inhibitor. Phosphodiesterases are enzymes that are found in almost all tissues in the body. Every change in the environment is perceived by the body and creates a stimulus. This is transmitted into the cell interior by messenger substances. These messenger substances are also known as second messengers. The second messengers include the substances cAMP (cyclic adenosine monophosphate) and cGMP (cyclic guanosine monophosphate). They are responsible for the stimulus response in the cell. This stimulus response can take place, for example, through a change in the metabolism of the cell. Signal transmission within the cell can be inhibited by phosphodiesterases. Phosphodiesterases can break down messenger substances such as cAMP or cGMP and thus render them ineffective.

Phosphodiesterase inhibitors, on the other hand, interfere with the work of the enzymes and thus promote signal transmission within the cell. Papaverine is a phosphodiesterase inhibitor that blocks phosphodiesterases, which make cAMP ineffective. In this way, they extend the effect of the messenger substance and intensify the effects of various stimuli. Since cAMP has a relaxing effect on the smooth muscles, papaverine has an antispasmodic and vascular relaxing effect.

Medical application & use

Papaverine is mainly used in heart surgery. There, the drug prevents cramping of blood vessels when gaining arteries for bypass operations. Papaverine is also used as an antispasmodic drug for stomach cramps, biliary colic and urinary tract spasms. However, in these indications it is increasingly being replaced by the antispasmodic propiverine, as this not only has an anticonvulsant but also anticholinergic effect.

Another area of ​​application for papaverine is erectile dysfunction in men. To do this, the drug is injected into the erectile tissue of the male member. The vasodilation then leads to increased blood flow to the penis and thus to an erection. This therapy is also known as erectile tissue auto-injection therapy (SKAT).

In rare cases papaverine is also used to treat peripheral or cerebral circulatory disorders. Therapy with the drug is controversial for these indications.

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Risks & side effects

When taking papaverine, neurological deficits such as hemiplegia, epileptic seizures, pupillary disorders or impaired consciousness can occur. The vasodilator effect of the drug can lead to a life-threatening drop in blood pressure. In addition, the pressure in the brain can increase. Overall, however, side effects are rare.

The injection of papaverine in erectile tissue autoinjection therapy, however, carries more risks. This can lead to a painful permanent erection. This form of permanent erection without arousal is known as priapism. The erection lasts longer than two hours and, if left untreated, can lead to severe erectile dysfunction.

Serious allergic reactions may also occur after injecting papaverine. These show up in the form of a rash, hives, tightness in the chest, or swelling on the body. If you experience these symptoms, you should see a doctor immediately. Excessive tiredness, irregular heartbeat, nausea, vomiting and yellowing of the skin and eyes (jaundice) also require immediate medical attention.

Minor side effects include diarrhea, constipation, dizziness, loss of appetite, upset stomach, or slight redness at the injection site. If these side effects persist or worsen, you should also see a doctor.