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Dopaminergics - Side Effects, Uses and Benefits

Type of Drug

Antiparkinson agents.

How the Drug Works

Parkinsonism is a neurological disease with a variety of causes characterized by tremor, rigidity, and disorders of posture and balance. The onset is slow and progressive, with symptoms advancing over months to years. Currently, there is no cure for the disease. The goal of therapy is to provide symptomatic relief and attempt to maintain the independence and mobility of the patient.

It is thought that the involuntary muscle movements (shaking) of Parkinson's disease are due to reduced amounts of the chemical transmitter dopamine in the nervous system. Levodopa is transformed by the body and the nervous system into dopamine. Carbidopa prevents levodopa from being broken down outside the nervous system. Bromocriptine stimulates dopamine receptors. The action of amantadine is not fully understood. It may increase dopamine concentrations in the nervous system or make the nervous system more sensitive to dopamine.


To treat Parkinson's disease, which may develop spontaneously or follow injury to the nervous system. Amantadine is also used for drug-induced extra pyramidal reactions (symptoms of Parkinson's disease caused by medication).

Unlabeled Uses: Occasionally doctors may prescribe levodopa for peppers zoster (shingles) and restless legs syndrome.


Carbidopa: Carbidopa had no antiparkinsonian effect when given alone. It is always used in combination with levodopa or carbidopa/levodopa products.

Neuroleptic malignant-like syndrome (NMS): NMS, including muscular rigidity, involuntary movements, altered consciousness, elevated body temperature, fast heartbeat, changes in blood pressure, mental changes, and increased serum enzymes, has been reported when antiparkinson agents were stopped suddenly. Do not abruptly reduce the dosage or discontinue use of amantadine or levodopa without consulting your doctor.

"On-off" phenomenon: Some patients who initially respond to levodopa therapy may develop the "on-off" phenomenon, a condition in which patients suddenly swing between an improved condition to a worsened condition. This effect may occur within minutes or hours and is associated with long-term levodopa therapy. Other patients may experience a deteriorating response. These conditions can be managed. Contact your doctor.

Pregnancy: There are no adequate and well-controlled studies in pregnant women. Use only if clearly needed and potential benefits to the mother outweigh the possible hazards to the fetus.

Breastfeeding: Use of amantadine, bromocriptine, and levodopa while breastfeeding is not recommended. It is not known if carbidopa appears in breast milk. Consult your doctor before you begin breastfeeding.

Children: Safety and effectiveness of amantadine in children younger than 1 year of age have not been established. Safety and effectiveness of bromocriptine in children younger than 15 years of age have not been established. Safety and effectiveness of carbidopa/levodopa in children younger than 18 years of age have not been established.

Elderly: Elderly patients may require less amantadine or carbidopa/levodopa than younger patients.

Lab Tests: Lab tests will be required to monitor therapy. Tests may include blood counts, eye tests, pituitary tests, blood pressure monitoring, and liver, kidney, and heart function tests.

Drug Interactions

Tell your doctor or pharmacist if you are taking or planning to take any over­the-counter or prescription medications or dietary supplements with dopaminergic agents. Doses of one or both drugs may need to be modified or a different drug may need to be prescribed. The following drugs and drug classes interact with dopaminergic agents:

Amantadine -

  • Anticholinergics (eg, belladonna)

  • Triamterene/hydrochlorothiazide (eg, oyazide)

Bromocriptine -

  • Antihypertensives (eg, diltiazem)

  • Ergot alkaloids (eg, ergotamine)

  • Erythromycin (eg, lIosone)

Carbidopa/levodopa -

  • Antihypertensives (eg, diltiazem)

  • Hydantoins (eg, phenytoin)

  • Iron salts (eg, ferrous fumarate)

Side Effects

Every drug is capable of producing side effects. Many dopaminergic users experience no, or minor, side effects. The frequency and severity of side effects depend on many factors including dose, duration of therapy, and individual susceptibility. Possible side effects include:

Digestive Tract: Nausea; vomiting; diarrhea; constipation; gas; appetite loss; stomach pain or cramps; gastrointestinal bleeding; indigestion; heartburn.

Nervous System: Uncontrolled movement (twitching) of face, eyelids, mouth, hands, or legs; abnormally slow movement; mood swings; mental changes; anxiety; fatigue; euphoria (exaggerated sense of well-being); delusions; hallucinations; abnormal dreams; confusion; weakness; agitation; nervousness; dizziness; fainting; orthostatic hypo tension (dizziness or lightheadedness when rising quickly from a sitting or lying position); headache; depression; increased tremor; incoordination; sleeplessness; faintness; "on-off" phenomenon; falling; dementia; light­headedness; irritability; drowsiness; vertigo (feeling of whirling motion).

Circulatory System: Palpitations (pounding in the chest); irregular heart­beat; chest pain; changes in blood pressure.

Skin: Flushing; rash; increased sweating; hives; itching; hair loss; a normal skin sensations.

Other: Difficult urination; urinary incontinence; difficulty swallowing; numb­ness; increased salivation; dry mouth or nose; grinding of the teeth; difficulty opening mouth; taste changes; bitter taste; burning tongue; general body discomfort; hot flashes; double vision; blurred vision; dilated pupils; weight changes; dark sweat, saliva, or urine; abnormal blood counts; abnormal liver, kidney, and heart function tests; back, leg, or shoulder pain; abnormal or difficult breathing; suicidal ideation; vein inflammation; visual disturbances; shortness of breath; fluid retention; frequent urination; persistent erection of the penis, accompanied by pain and tenderness; urinary retention; nasal congestion; throat pain; intestinal ulcer; cough; hoarseness; sense of stimulation; hiccups.