Levodopa

A to Z Drug Facts

 Action Crosses the blood-brain barrier and is converted to dopamine in basal ganglia and periphery.

 Indications Treatment of idiopathic, postencephalitic and symptomatic parkinsonism. Unlabeled use(s): Relief of herpes zoster (shingles) pain and restless leg syndrome.

 Contraindications Narrow-angle glaucoma; concomitant MAO inhibitor therapy (excluding MAO inhibitor-type B agents such as selegiline); history of or suspected melanoma.

 Route/Dosage

ADULTS: PO 0.5 to 1 g/day in 2 to 4 divided doses initially. Increase dosage gradually in increments £ 0.75 g/day q 3 to 7 days as tolerated (maximum 8 g/day).

 Interactions

Anticholinergics, benzodiazepines, hydantoins, methionine, papaverine, pyridoxine, tricyclic antidepressants: May reduce the effectiveness of levodopa. MAO inhibitors (except selegiline): Causes hypertensive reactions.

 Lab Test Interferences

Antiglobulin 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.

 Adverse Reactions

CV: Cardiac irregularity or palpitation; orthostatic hypotension; hypertension; phlebitis. CNS: 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). DERM: Flushing; skin rash; sweating. EENT: Blepharospasm; diplopia; blurred vision; dilated pupils; impaired taste perception; oculogyric crisis. GI: Anorexia; nausea; vomiting; abdominal pain; distress; dry mouth; dysphagia; excessive salivation; bruxism; GI bleeding; duodenal ulcer. GU: Urine retention; urinary incontinence; priapism. HEMA: Hemolytic anemia; anemia; agranulocytosis; leukopenia. HEPA: Elevated AST, ALT, LDH. RESP: Bizarre breathing patterns. OTHER: 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.

 Precautions

Pregnancy: Pregnancy category undetermined. Lactation: Undetermined. Do not use in nursing mothers. Children: Safety and efficacy in children < 12 yr not established. Concomitant conditions: Use cautiously in patients with severe cardiovascular or pulmonary disease; renal, hepatic or endocrine disease; affective disorder; major psychosis; and cardiac arrhythmias. Dosage reduction: Decrease levodopa dose by 75% to 80% when used in combination with carbidopa. MI: Administer cautiously to patients with history of MI who have residual arrhythmias. Administer drug in facility with coronary or intensive care unit. Psychiatric patients: 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.

 Administration/Storage

• 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.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Assess for skin lesions or history of malignant melanoma.
• Determine if patient is receiving MAO inhibitor. MAO inhibitor therapy must be discontinued at least 3 wk before levodopa regimen is instituted.
• Perform complete baseline assessment of parkinsonian signs and symptoms before instituting therapy.
• Monitor BP closely for hypotension if patient is taking antihypertensives concurrently.
• Assist with ambulation during initial phase of therapy because of dizziness due to hypotension.
• Monitor protein intake because absorption of levodopa is decreased in the presence of high-protein foods.
• If uncontrollable movements, mental changes (eg, depression, paranoia), palpitations, difficult urination or severe or persistent nausea and vomiting occur, notify physician.
• Offer support to patient and family because relief of parkinsonian symptoms may take several weeks to months after therapy is initiated.

 Patient/Family Education

• 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 physician 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 physician: 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 side effect.
• 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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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts