The drug ropinirole belongs to the dopamine agonists. It is used to treat Parkinson’s disease and restless legs syndrome.
What is ropinirole?
The drug ropinirole belongs to the group of dopamine agonists. It is used to treat Parkinson’s disease and restless legs syndrome. Ropinirole is a medicinal substance that belongs to the group of dopamine receptor agonists. Its structure is similar to that of the important neurotransmitter dopamine. However, unlike numerous other dopamine agonists, it is not an ergot alkaloid. In the early stages of Parkinson’s disease, ropinirole is used as a single agent. As the disease progresses, it can be combined with levodopa (L-dopa). In monotherapy, ropinirole does not achieve the efficacy of levodopa, but is considered more effective than bromocriptine. In combination treatment, partial replacement of levodopa administration is possible.
Pharmacologic Action
In PD, there is a deficiency of dopamine in the brain. This substance is essential for the control of human movement. In healthy people, production and breakdown of the neurotransmitter dopamine occur constantly. However, if the onset of Parkinson’s disease occurs, dopamine production is continuously reduced, and the breakdown of the substance is not subject to any restrictions. Even after a short time, the lack of dopamine becomes noticeable through typical Parkinson’s symptoms such as slowed movements, muscle tremor and muscle rigidity. Dopamine itself cannot be supplied in the form of tablets, because in this way it is not possible to penetrate the protective barrier that surrounds the human brain. However, to compensate for the lack of dopamine, there is an option to take various drugs. One of these drugs is the dopamine receptor agonist ropinirole. Although this substance has a different chemical structure than dopamine, it targets the same binding sites as the neurotransmitter, thus achieving comparable effects. In contrast to dopamine, ropinirole also has the ability to cross the blood–brain barrier to the brain. This allows the drug to compensate for the lack of dopamine, which in turn has a positive effect on Parkinson’s symptoms. Like the dopamine agonist pramipexole, ropinirole has the property of binding to D3 receptors. These are located on the brain cells. Due to the binding, the patient implements his movements better and at the same time increases his mobility. The half-life of 6 to 24 hours is significantly longer than that of levodopa, which is only 1.5 hours. This results in lower fluctuations in effect.
Medical use and application
The main indication for ropinirole is Parkinson’s disease. Usually, the active ingredient is taken together with levodopa. Another area of application is the so-called restless legs syndrome. In this case, affected individuals suffer from constant restlessness of their legs. The uncontrollable urge to move becomes particularly noticeable at night. It is not uncommon for accompanying symptoms such as shooting pains and muscle twitching to occur. Doctors also blame a lack of dopamine for restless legs syndrome. Thus ropinirole shows positive effects in the treatment of the disease. In order to stimulate the brain cells in the long term, it is necessary to take ropinirole over a longer period of time. Ropinirole is now administered as a sustained-release tablet. This preparation releases the active ingredient continuously over a period of 24 hours. The tablet consists of three layers. These are the central layer, in which the ropinirole is embedded, and two inactive boundary layers. Ropinirole tablets can be taken both during and after meals. It is important to always take the drug at the same time, if possible.
Risks and side effects
Taking ropinirole may result in unwanted side effects. However, this does not always occur, as each patient reacts individually to medicines. Most commonly, affected individuals suffer from insomnia, water retention in the legs, constipation, nausea, involuntary movements, lightheadedness, dizziness, confusion, or hallucinations.Sometimes the movement disorders associated with Parkinson’s disease may worsen, or low blood pressure or sudden falling asleep may occur. Some patients also experience unusual side effects such as pathological gambling addiction or increased sexual desire. If a patient suffers from pronounced mental disorders, therapy with ropinirole may only be given if the treating physician considers the benefits of the treatment to outweigh the risks. There are also some contraindications to treatment with ropinirole. These are hypersensitivity to the drug, the existence of a tumor in the adrenal gland (from which hormones are produced), and allergies to drugs such as neuroleptics. Caution is also advised in cases of severe cardiovascular disease or psychosis. In addition, interactions with other drugs must be taken into account. For example, ropinirole increases the effect of other dopamine agonists such as amantadine and selegelin. Furthermore, it is not recommended to take medications containing dopamine, epinephrine, norepinephrine, maprotiline, venlafaxine, or desipramine without medical supervision. The same applies to circulatory medications or drugs that lower blood pressure. Smoking also plays a role. Thus, tobacco use negatively affects the potency of ropinirole.
