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Class: Antiparkinson agent
- Capsules 100 mg
- Capsules 250 mg
- Capsules 500 mg
Crosses the blood-brain barrier and is converted to dopamine in basal ganglia and periphery.
Absorbed from the small bowel. T max is 0.5 to 2 h and may be delayed in presence of food. Rate of absorption is dependent upon rate of gastric emptying, pH of gastric juice, and length of time drug is exposed.
Does not cross the blood-brain barrier.
Metabolites are dopamine and homovanillic acid (HVA). Extensively metabolized (greater than 95%) in the periphery and by the liver.
Plasma t ½ is 1 to 3 h. Excreted primarily in the urine; 13% to 42% of HVA excreted in the urine within 24 h.
Indications and Usage
Treatment of idiopathic, postencephalitic, and symptomatic parkinsonism.
Relief of herpes zoster (shingles) pain and restless leg syndrome.
Narrow-angle glaucoma; concomitant MAOI therapy (excluding MAOI-type B agents such as selegiline); history of or suspected melanoma.
Dosage and AdministrationAdults
PO 0.5 to 1 g/day in 2 to 4 divided doses initially. Increase dosage gradually in increments up to 0.75 g/day every 3 to 7 days as tolerated (max, 8 g/day).
- Give medication with food to reduce nausea.
- Tablets can be crushed and capsules opened for mixing with small amount of fruit juice for patients being given tube feedings.
Store at room temperature in light-resistant container.
Drug InteractionsAnticholinergics, benzodiazepines, hydantoins, methionine, papaverine, pyridoxine, tricyclic antidepressants
May reduce the effectiveness of levodopa.MAOIs (except selegiline)
Causes hypertensive reactions.
Laboratory Test InteractionsAntiglobulin Coombs' test
With extended therapy, drug may cause false-positive results.Uric acid study
May result in elevated values with colorimetric method but not with uricase method.
Cardiac irregularity or palpitation; orthostatic hypotension; hypertension; phlebitis.
Ataxia; headache; dizziness; numbness; weakness; faintness; confusion; insomnia; nightmares; mental changes (eg, psychosis, paranoia, depression, dementia, hallucinations, delusions); agitation; anxiety; fatigue; euphoria; psychopathology; adventitious movements (eg, choreiform or dystonic movements); increased hand tremor; muscle twitching; trismus; bradykinesia (“on-off” phenomenon).
Flushing; skin rash; sweating.
Blepharospasm; diplopia; blurred vision; dilated pupils; impaired taste perception; oculogyric crisis.
Anorexia; nausea; vomiting; abdominal pain; distress; dry mouth; dysphagia; excessive salivation; bruxism; GI bleeding; duodenal ulcer.
Urine retention; urinary incontinence; priapism.
Hemolytic anemia; anemia; agranulocytosis; leukopenia.
Elevated AST, ALT, LDH.
Bizarre breathing patterns.
Malaise; hot flashes; weight gain or loss; dark sweat or urine; latent Horner's syndrome; elevated BUN, bilirubin, alkaline phosphatase, and protein-bound iodine; activation of malignant melanoma.
Pregnancy category undetermined.
Undetermined. Do not use in breast-feeding mothers.
Safety and efficacy in children younger than 12 yr of age not established.
Use with caution in patients with severe CV or pulmonary disease; renal, hepatic or endocrine disease; affective disorder; major psychosis; and cardiac arrhythmias.
Decrease levodopa dose 75% to 80% when used in combination with carbidopa.
Administer cautiously to patients with history of MI who have residual arrhythmias. Administer drug in facility with coronary or intensive care unit.
Use cautiously. Observe all patients for development of depression or suicidal ideation.
Upper GI hemorrhage
May occur in patients with prior history of peptic ulcer.
Shock, coma, blepharospasm, arrhythmias, seizures, CNS depression, muscle twitching.
- Advise patient to take medication with food.
- Teach patient to avoid sudden position changes to avoid orthostatic hypotension.
- Inform patient that fluctuation in effectiveness of levodopa sometimes occurs with long-term therapy. Instruct patient to notify health care provider if fluctuation in effectiveness is experienced.
- Advise patient to avoid use of OTC vitamins, fortified cereals and vitamin B 6 , which reverse effects of levodopa.
- Warn patient not to increase dosage in an attempt to reduce parkinsonian symptoms more quickly. Noticeable lessening of symptoms may take more than 6 mo to occur.
- Advise patient to report the following symptoms to health care provider: uncontrolled movements, mood or mental changes, irregular heartbeats, difficulty in urination, severe or persistent nausea or vomiting, worsening of parkinsonian symptoms.
- Advise patient that levodopa may cause urine and perspiration to become dark, which is a harmless adverse reaction.
- Inform patient that drug may cause drowsiness and to use caution while driving or performing tasks that require mental alertness.
- Instruct patient to take sips of water frequently, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs.
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