Benserazide is an active substance that is not available as a mono-preparation, but is always administered in combination with levodopa. Both agents are prescribed exclusively for the treatment of Parkinson’s disease and restless legs syndrome. Benserazide supports the prodrug levodopa so effectively because it acts directly on the periphery.
What is benserazide
Benserazide is always administered in combination with levodopa. Both agents are prescribed exclusively for the treatment of Parkinson’s disease and restless legs syndrome. Benserazide (chemical formula: C10H15N3O5) occurs as benserazide hydrochloride only together with levodopa. It is a white to yellowish, crystalline, non-water-soluble powder. It belongs to the group of benserazide decarboxylase inhibitors. As the name suggests, it blocks the action of dopamine decarboxylase, an enzyme that breaks down the neurotransmitter dopamine in the blood and gut. Benserazide cannot cross the blood–brain barrier and acts only peripherally (i.e., outside the central nervous system). It prevents L-dopa degradation at the periphery, ensuring that the dopamine precursor can pass the blood–brain barrier and produce much-needed dopamine in the brain. In the oral tablets for Parkinson’s disease and restless legs syndrome, both active substances are present in a ratio of 4:1 (L-dopa:benserazide). They are sold under the trade names Madopar, Levopar, and Levodopa comp. and contain dosages of 100 mg/25 mg, 200 mg/50 mg, and 50 mg/12.5 mg.
Pharmacologic Action
Benserazide, together with levodopa, helps to relieve the symptoms of tremor (tremor), muscle rigidity (rigor), and impaired movement (akinesia) typical of Parkinson’s disease, helping the affected person to move more freely and slowing the progression of the disease. Since the neurotransmitter dopamine, which effectively reduces these symptoms, cannot cross the blood-brain barrier by itself, it is administered in the form of its precursor (L-dopa). This drug, in turn, is largely broken down in the body by an enzyme called dopamine decarboxylase before it can reach where it is needed to make more dopamine (the brain). Since the patient would have to be given too high a dose of L-dopa for any of the active ingredient to reach the brain, it is given along with benserazide. Benserazide hydrochloride inhibits the activity of the L-dopa-degrading enzyme very effectively because its molecular similarity to levodopa allows it to bind to the enzyme and deactivate its catalytic center. Thus, L-dopa is able to cross the blood-brain barrier unimpeded and in full dose. Another pharmacological effect of benserazide is that it prevents prolactin secretion in lactating women. This hormone is responsible for the formation of breast milk.
Medicinal use and application
The combination drug levodopa + benserazide is indicated for long-term therapy in patients with Parkinson’s disease and with restless legs syndrome. In addition, it is used in people who show Parkinson’s-like symptoms, although this must not be a side effect of any medication administered. Parkinson’s patients regain their mobility at least partially through the active substances. In addition, the rapid progression of the disease is inhibited. In the case of restless legs syndrome, which is apparently also caused by a dopamine deficiency in the brain, the symptoms that occur at night in bed (uncontrollable urge to move, abrupt pain and muscle twitching) are alleviated. Patients find nocturnal rest. In addition, the active ingredient combination levodopa + benserazide is used to diagnose “restless legs syndrome”: If the complaints are noticeably alleviated, the affected person is actually suffering from this disorder. For this purpose, the physician usually administers the preparation in the form of tablets of 100 mg/25 mg. The combination drug can also be combined well with other approved drugs for Parkinson’s disease.
Risks and side effects
When taking levodopa + benserazide, the following side effects are very common in the indication of Parkinson’s disease: Loss of motor control over the mouth, tongue, and head; impaired body movements; urine discoloration; nausea; and vomiting.Commonly observed are anxiety, depression, restlessness, confusion, drowsiness, insomnia, loss of appetite, sweating, tremors, fatigue, indigestion, dry mouth, and abdominal pain. Restless Legs Syndrome patients prescribed the drug very often have sleep disturbances, depression, diarrhea, nausea and vomiting. Altered taste sensation, hallucinations, anxiety, and cardiac arrhythmias are common. Levodopa + benserazide should not be used if the patient has hypersensitivity to the active ingredients, pheochromocytoma (adrenal tumor), severe hyperthyroidism, psychosis, palpitations, narrow-angle glaucoma, severe liver, heart, kidney, metabolic, and bone marrow disease, or is under 25 years of age. It should also not be administered during pregnancy. In animal studies, embryonic damage occurred. No medical data are yet available for humans. Breastfeeding women should be sure to stop breastfeeding if they must take the drug. People with previous gastrointestinal ulcers, myocardial infarction, coronary heart disease, cardiac arrhythmias, open-angle glaucoma, bone softening, and diabetes will receive it only if there is an urgent medical indication. You will be monitored regularly by a doctor during treatment. If the combination of active substances against Parkinson’s disease and Restless Legs Syndrome is administered together with painkillers (opiates), neuroleptics, iron preparations, acid-binding drugs (antacids), phenytoin, papaverine, antihypertensive and circulatory supporting drugs, its effect is decreased. Enhancement of the effect of levodopa + benserazide occurs when the drug is taken with selective MAO-B inhibitors. For example, adjustment of the amantadine or selegelin dose may be required. MAO-A inhibitors should be discontinued 14 days before taking levodopa + benserazide, otherwise the patient may experience a crisis increase in blood pressure. The gastric drug metoclopramide ensures faster absorption of the active substances and more side effects.