Parkinson’s disease is a long term disease where the patient needs to take medicines on a regular basis for relief of the symptoms> It is important for both the Parkinson’s patient and care givers to realize that these medicines might have various types of interactions with other drugs. Some of these drug interactions can be quite severe, therefore additional medicines should be taken only after consulting a doctor.
What is Drug Interaction?
Medicines are used to treat certain conditions or illnesses, but when two or more medicines are used simultaneously, they may interact with each other and cause complications or unwanted side effects. Drug interactions may occur with prescription drugs, over-the-counter (OTC) medicines, herbal remedies, or dietary supplements, so it is important that the patient realizes the dangers of mixing drugs without consulting a doctor.
Parkinson’s Disease Medicines
The drug therapy most commonly used in Parkinson’s disease usually consists of the following :
- Levodopa + peripheral decarboxylase inhibitors such as carbidopa and benserazide.
- Dopamine receptor agonists – pramipexole, ropinirole, and rotigotine.
- MAO-B inhibitors – selegiline and rasagiline.
- COMT inhibitors – entacapone
- Anticholinergics – benzhexol and orphenadrine
Drug Interactions with Parkinson’s Disease Medicines
Since this is the most widely used medicine in Parkinson’s disease, its drug interactions should be understood by all Parkinson’s patients. Certain medicines decrease effectiveness of levodopa hence the dose of levodopa may have to be adjusted if used together. These include
- Anticholinergics – sometimes used in addition to levodopa for treatment of symptoms in Parkinson’s disease. Over-the-counter cough and cold medicines contain anticholinergics such as diphenhydramine, chlorpheniramine, and phenylephrine.
- Antispasmodics used for treating stomach or uterine cramps also contain anticholinergics such as dicyclomine and hyoscyamine.
- Anti-allergic medicines (like anti-histamines)
- Antiepileptic drugs such as phenytoin
- Sedatives such as diazepam, lorazepam and alprazolam.
- Multivitamins, specially vitamin B-6 or pyridoxine, and minerals such as iron.
- Tricyclic antidepressants such as amitriptyline
- Metoclopramide – used to control nausea and vomiting.
Certain medicines help to increase the effect of levodopa. They include
- Medicines containing acetaminophen, used for pain, headache, and fever.
- Antacids and other medicines containing aluminum, calcium, and magnesium.
The above medicines should not be used to enhance the effect of levodopa.
Levodopa may potentiate the action of antihypertensives, causing excessive lowering of blood pressure when used concurrently. Levodopa may cause severe hypertensive reactions if taken by patients treated with MAO (monoamine oxidase) inhibitors such as furazolidone or procarbazine within the last 14 days.
Other Parkinson’s Drugs
Similar drug interactions are possible with all other medicines used in Parkinson’s disease. In addition,
- Alcohol intake may cause CNS depression when used along with Parkinson’s disease medicines.
- Antibiotics such as ciprofloxacin, norfloxacin, and ofloxacin may cause drug interactions with pramipexole, ropinirole, or rotigotine.
- Entacapone may react with antibiotics such as ampicillin, erythromycin, and chloramphenicol.
- Narcotic pain relievers such as codeine may react with entacapone or other drugs.
- Quinine or quinidine may interfere with renal clearance of amantadine.
Various other drug interactions are possible and you should consult with your doctor before taking any other medication or supplement, whether an OTC (over-the-counter) medicine, scheduled drug or a herbal remedy.