Levodopa(lee voe doe’ pa)
PREGNANCY CATEGORY C
Drug class
Antiparkinsonian
Therapeutic Actions
Biochemical precursor of the neurotransmitter dopamine, which is deficient in the basal ganglia of parkinsonism patients; unlike dopamine, levodopa penetrates the blood–brain barrier. It is transformed in the brain to dopamine; thus, levodopa is a form of replacement therapy. It is efficacious for 2–5 yr in relieving the symptoms of parkinsonism but not drug-induced extrapyramidal disorders.
Indications
Treatment of parkinsonism (postencephalitic, arteriosclerotic, and idiopathic types) and symptomatic parkinsonism following injury to the nervous system by carbon monoxide or manganese intoxication
Given with carbidopa (Lodosyn; fixed combinations, Sinemet), an enzyme inhibitor that decreases the activity of dopa decarboxylase in the periphery, thus reducing blood levels of levodopa and decreasing the intensity and incidence of many of the adverse effects of levodopa
Unlabeled uses: Relief of herpes zoster (shingles) pain; restless legs syndrome
Contraindications and Cautions
Contraindicated with hypersensitivity to levodopa; glaucoma, especially angle-closure glaucoma; lactation.
Use cautiously in psychiatric patients, especially the depressed or psychotic; and with severe CV or pulmonary disease; occlusive cerebrovascular disease; history of MI with residual arrhythmias; bronchial asthma; renal, hepatic, endocrine disease; history of peptic ulcer; pregnancy.
Available Forms
Available only in combination products
Dosages
Adults
Individualize dosage. Increase dosage gradually to minimize side effects; titrate dosage carefully to optimize benefits and minimize side effects. Initially, 0.5–1 g PO daily divided into two or more doses given with food. Increase gradually in increments not exceeding 0.75 g/day every 3–7 days as tolerated. Do not exceed 8 g/day, except for exceptional patients. A significant therapeutic response may not be obtained for 6 mo. Only available in combination forms.
Pediatric patients
Safety for use in children younger than 12 yr not established.
