Apomorphine‘s similarity to dopamine, a neurotransmitter produced naturally in the body, makes it one of the most effective dopamine mimics available to medicine and pharmacy today. Formerly used primarily as an emetic, apomorphine now serves a broader range of actions in a variety of indication settings.
What is apomorphine?
The agent receives its most common and important use in the treatment of late-stage Parkinson’s disease, as a continuous infusion or subcutaneous injection. Apomorphine belongs (eponymously) to the aporphine aclaloids. The morphine derivative is obtained by heating morphine with concentrated hydrochloric acid. Its structure is closely related to that of human dopamine. The rather water-resistant crystals of the salt apomorphine hydrochloride can appear in different colors, white, slightly yellowish-brownish or gray-green. It turns green when exposed to light. Although it belongs to the dopamine agonists, the morphine derivative itself does not have an opioid effect. The triggering effect is more like that of the endogenous messenger dopamine. The vomiting-inducing apomorphine was previously used primarily in cases of poisoning. As of 2001, it participated in the treatment of male erectile dysfunction in the dosage form of a lozenge that acted on the oral mucosa under the tongue. Apomorphine was occasionally used as an adjunctive measure in drug withdrawal. Its most common and important use is in the treatment of late-stage Parkinson’s disease, as a continuous infusion or subcutaneous injection. Apomorphine is also used in homeopathy.
Pharmacological action
The proerectile action of apomorphine, unlike libido-enhancing preparations, is more centrally mechanical. Via dopamine binding in the hypothalamus, the drug achieves relaxation of the muscles in the penile corpus cavernosum via several neuronal steps. The improved blood supply promotes erectile function. Since the active ingredient is very well absorbed by the cells, administration as a tablet under the tongue is most successful. Here it shows the desired success within 20 minutes due to rapid absorption in the mucosa. Apomorphine does not produce compulsive behavioral disturbance, leaves the sex drive unchanged and does not negatively affect the psyche. Apomorphine is particularly suitable for the treatment of Parkinson’s disease patients in the late phase. The symptoms of this disease are due to dopamine deficiency. The cause is loss or destruction of dopamine-producing nerve cells in the central nervous system. Normal movement is sensitively disturbed, tremor (trembling), akinesia (movement disorder) and rigor (strong muscle tension, muscle rigidity) are the consequences.
Medical application and use
Apomorphine is well suited to reduce the motor symptoms of Parkinson’s disease concomitantly with the administration of levodopa because of its property as a dopamine receptor agonist. Its action is in the brain, where it mimics the action of the body’s own neurotransmitter. However, it is not considered a priority drug because of its severe side effects. The emetic effect also starts right here, when certain dopamine receptors in the central nervous system are stimulated. To empty the patient’s stomach, the drug domperidone is given two days before treatment begins. As an emetic, apomorphine has since been replaced by far more tolerable agents because of the risk of cardiovascular disturbance or respiratory paralysis, especially in children. Negatively, apomorphine had been noticed in the use of illegal drugs in the drug scene.
Risks and side effects
The side effects that occur may depend on the dosage form (injection, tablet, infusion, ointment) and the frequency of use. The common combination of apomorphine with levodopa makes the causative agents of the drug side effects that actually occurred difficult to identify. In addition to an increased tendency to nausea and vomiting, hypotension (drop in blood pressure when standing up from a lying position), uncontrollable voluntary movements, confusion or drowsiness, hallucinations, digestive and respiratory disturbances frequently occurred. Infections, mouth ulcers, disorders of taste occur, as well as inflammation of the nasal or pharyngeal mucosa. More rarely, the increased formation of white blood cells and psychosis. Obsessive behavioral problems may necessitate a change in treatment.Interactions exist with clozapine (agent in the treatment of mental-nervous symptoms) and with neuroleptics taken at the same time. Apomorphine may increase the effect of antihypertensives and alcohol. Completely discouraged from use to pregnant and lactating women, as well as children and adolescents, people with weakness of liver and kidney function, with a pre-existing tendency to nausea, with hypotension, cardiovascular or pulmonary diseases. The elderly and debilitated should be prescribed apomorphine only after careful benefit/risk assessment.
