Levodopa is a dopamine precursor, a substance that is converted into dopamine by an enzyme in the brain. The use of levodopa was a breakthrough in the treatment of PD. Unfortunately, patients experienced debilitating side effects, including severe nausea and vomiting. With increased dosing and prolonged use of levodopa, patients experienced other side effects including dyskinesias (spontaneous, involuntary movements) and "on-off" periods when the medication will suddenly start or stop working.
Check with a doctor before taking any of the following to avoid possible interactions: antacids, anti-seizure drugs, anti-hypertensives, anti-depressants and high protein food.
Combining Levodopa with Carbidopa (Sinemet) represented a significant improvement in the treatment of Parkinson's disease. The addition of carbidopa prevents levodopa from being metabolized in the gut, liver and other tissues, and allows more of it to get to the brain. Therefore, a smaller dose of levodopa is needed to treat symptoms. In addition, the severe nausea and vomiting often associated with levodopa treatment was greatly reduced.
Consult a doctor before taking any medications to avoid possible interactions. In particular, antacids, anti-seizure drugs, anti-hypertensives, anti-depressants and high protein food may adversely affect the function of Levodopa/carbidopa.
Stalevo (carbidopa, levodopa and entacapone) is a new (September 2003) combination tablet for patients who experience signs and symptoms of end-of-dose "wearing-off." The tablet combines carbidopa/levodopa (the most widely used agent for PD), with entacapone. While carbidopa reduces the side effects of levodopa, entacapone extends the time levodopa is active in the brain (up to 10 percent longer). The same drugs that interact with carbidopa/levodopa and entacapone interact with Stalevo.
Symmetrel (amantadine hydrochloride) is thought to work in PD because it has several actions. It activates both the release of dopamine from storage sites and possibly blocks the re-uptake of dopamine into nerve terminals. It also has a glutamate receptor blocking activity. Its dopaminergic actions result in its usefulness in reducing dyskinesia induced by levodopa. It is thus called an indirect-acting dopamine agonist, and is widely used as an early monotherapy (treatment of a condition by means of a single drug), with the more powerful Sinemet added when needed. Unfortunately, its benefit in more advanced PD is often short-lived, with patients reporting a fall-off effect.d
Symmetrel may interact with Cogentin (benztropine), Disipal (orphenadrine), Sinemet (levodopa), Artane (trihexyphenidyl), amphetamines and alcohol.
Anticholinergics (trihexyphenidyl, benztropine mesylate, procyclidine, etc.) do not act directly on the dopaminergic system. Instead they act to decrease the activity of another neurotransmitter, acetylcholine. There is a complex interaction between levels of acetylcholine in the brain and levels of dopamine. Many clinicians find that if an agonist or levodopa does not relieve tremor, then the addition of an anticholinergic drug is often effective. Adverse effects include blurred vision, dry mouth and urinary retention. These drugs may be contraindicated in older patients since they can cause confusion and hallucination.d
Check with a doctor before using anticholinergics with anti-histamines, Haldol, Thorazine, Symmetrel, Clozaril and alcohol.
Selegiline or deprenyl (Eldepryl) has been shown to delay the need for Sinemet when prescribed in the earliest stage of PD, and has also been approved for use in later stages to boost the effects of Sinemet. Eldepryl may interact with anti-depressants, narcotic pain killers and decongestants. Check with a doctor before taking any new medications.
Dopamine agonists are drugs that activate dopamine receptors directly, and can be taken alone or in combination with Sinemet. Agonists available in the United States include bromocriptine (Parlodel), pergolide (Permax), pramipexole (Mirapex) and ropinirole (Requip).
Consult a doctor before taking any of the following to avoid possible interactions: alcohol, anti-psychotics, medications that lower blood pressure, Navane (thiothixene), Taractan (chlorprothixene), Haldol (haloperidol), Reglan (metoclopramide), phenothiazines, thiozanthenes, cimetidine, phenothiazines, butyrophenones, Cipro and benzodiazepines.
COMT inhibitors such as tolcapone (Tasmar) and entacapone (Comtan) represent a different class of Parkinson's medications. These drugs must be taken with levodopa. They prolong the duration of symptom relief by blocking the action of an enzyme which breaks down levodopa.
*** Side Effects from Medications - Like the symptoms of PD themselves, the side effects caused by Parkinson's medications vary from patient to patient. They may include dry mouth, nausea, dizziness, confusion, hallucinations, drowsiness, insomnia, and other unwelcome symptoms. Some patients experience no side effects from a drug, while others may have to discontinue its use because of them.
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