Reserpine is a drug used as an antihypertensive and as a neuroleptic. Originally, the active ingredient comes from some plants in the snakeroot group.
What is reserpine?
Reserpine is a drug used as an antihypertensive and as a neuroleptic. Reserpine is a chemical compound that occurs naturally in plants. The substance belongs to the indole alkaloids. Indole alkaloids are the largest group within the alkaloids. They are characterized by their indole or indoline base. The drug reserpine became known in Western medicine in particular through the plant Rauvolfia serpentina from India. Reserpine was one of those drugs that ushered in the era of modern psychomedication. The substance was first used in psychiatric institutions for schizophrenia as a neuroleptic. Neuroleptics are now also known as antipsychotics. These are drugs that have an antipsychotic and / or sedative effect. Later, reserpine was used primarily as a treatment for high blood pressure (hypertension). Today, reserpine is not the drug of first choice either as a neuroleptic or as an antihypertensive agent because of various side effects.
Pharmacologic action
The action of reserpine in the human body can be divided into a central and a peripheral action. Reserpine inhibits the neurotransmitter norepinephrine in the sympathetic nervous system. The postganglionic system is particularly affected. Although the depletion of the neurotransmitter causes more nerve cells to discharge than before the drug was taken, the stimulus is not carried away to the periphery of the body. By inhibiting the sympathetic nervous system, the heart rate is lowered and thus blood pressure is reduced accordingly. At the same time, reserpine lowers dopamine and serotonin concentrations in the central nervous system. At the cellular level, reserpine also empties the stores of biogenic amines. These include neurotransmitters such as serotonin, dopamine and norepinephrine. In addition, the neurotransmitters can no longer be taken up into the cell via the vesicles. Because of these mechanisms of action, the antipsychotic and sedative effects of reserpine occur.
Medical application and use
Reserpine was first isolated from the plant Rauvolfia serpentina in 1952. While the drug was commonly used as an antihypertensive and neuroleptic in the 1950s, 1960s, and 1970s, reserpine is rarely found in medications today. The substance has been replaced by more effective drugs with fewer side effects. In pharmacologically relevant quantities, reserpine is now only on the market as a component of diuretics. Reserpine is combined with thiazide diuretics, dihydralazine and hydrochlorothiazide. However, the prescription frequency of these remaining preparations with reserpine is also decreasing. Currently, there is also a homeopathic preparation on the market containing reserpine as a pure substance in the potency D3 32 milligrams. Reserpine can also be used diagnostically. Thus, the drug is sometimes used when a carcinoid is suspected. Carcinoids are neuroendocrine tumors that produce tissue hormones such as kallikrein and serotonin. The reserpine test is a provocation test. Carcinoids usually produce large amounts of serotonin. Reserpine ensures the release of serotonin from the tumor cells, so that the typical symptoms of carcinoids are more pronounced after reserpine administration. In addition, the urine shows a greatly increased concentration of 5-HIES. 5-HIES is a degradation product of serotonin.
Risks and side effects
Reserpine has fallen into disrepute primarily because of its consequently serious side effects. Reserpine decreases the availability of catecholamines, thus lowering sympathetic tone. Acetylcholine, another neurotransmitter, remains unaffected by this effect, however, so that the parasympathetic nervous system predominates in its activity as a result of drug intake. Constriction of the pupils, drooping eyelids and swelling of the nasal mucous membranes may occur. This phenomenon is also known as reserpine rhinitis. Other side effects resulting from the increased activity of the parasympathetic nervous system include loss of potency and libido and diarrhea. Gastric and intestinal ulcers may develop. In addition to the quite desirable bradycardia, a position-induced drop in blood pressure may also develop.This orthostatic hypotension can be so severe that the affected person loses consciousness when standing up quickly. Reserpine can harm the unborn or newborn child through breast milk and across the placenta. If mothers have taken reserpine in the last trimester of their pregnancy, infants are significantly more likely to suffer from breathing and drinking disorders after birth. Newborns often show marked lethargy. The fetus may exhibit a slowed heartbeat. In women, reserpine may also cause menstrual cramps. In the central nervous system, side effects result primarily from a deficiency of serotonin and dopamine. So-called extrapyramidal motor disorders and parkinsonism occur, with symptoms such as muscle rigidity, immobility, muscle tremors, and postural instability. When reserpine is overdosed, blood pressure, heart rate and body temperature drop rapidly. Those affected suffer from severe drowsiness. Convulsions may also occur. It should be noted that if tricyclic or tetracyclic antidepressants are previously administered, a so-called reserpine reversal occurs. In this case, motor excitation is not inhibited as intended, but increased. Indirect sympathomimetics do not have any effect if pretreated with reserpine. In contrast, the lowering effect of antidiabetic drugs on blood glucose levels is enhanced by reserpine. The effect of antiparkinsonian drugs such as levodopa or bromocriptine is impaired. Patients taking cardiac glycosides and reserpine in parallel may develop cardiac arrhythmias. Reserpine is contraindicated in the presence of a history of depressive episodes, existing gastric and duodenal ulcers, and bronchial asthma.
