levodopa; L-3-hydroxytyrosine; L-3,4-dihydroxyphenylalanine; L-dopa (Dopar, Larodopa, Inbrija)
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Introduction
Tradenames: Dopar, Larodopa.
Indications
- symptomatic treatment of Parkinson's disease
- used to provide relief from Herpes zoster pain
- fibromyalgia
- restless legs syndrome
Contraindications
- narrow-angle glaucoma
- concurrent MAO inhibitor therapy
- melanoma or undiagnosed skin lesion
Caution:
- patients with history of myocardial infarction
- arrhythmias
- asthma
- glaucoma
- peptic ulcer disease
- sudden discontinuation of L-dopa can worsen symptoms of parkinsonism
Dosage
- start 250-500 mg PO BID, max 8 g/day
- take all doses with food
- avoid vitamin B6 (pyridoxine)
Tabs: 100, 250 500 mg.
* inhalation powder (Inbrija)[5]
- inhlation powder bypasses liver metabolism moving from lungs to the bloodstream[5]
Pharmacokinetics
- good oral bioavailability
- metabolized by peripheral decarboxylation unless given concurrently with carbidopa
- metabolized in the liver
- excreted in the urine
- plasma 1/2life is 1-3 hours
- a significant therapeutic response may occur in 2-3 weeks, but may not be seen for up to 6 months
elimination via liver
1/2life = 1-3 hours
Adverse effects
- common (> 10%)
- less common (1-10%)
- eyelid spasms, anorexia, diarrhea, dry mouth, headache, muscle twitching, discoloration of urine/sweat
- uncommon (< 1%) duodenal ulcer, hypertension, hemolytic anemia, GI bleeding, blurred vision
- other:
- bradykinetic episodes
- 'on-off' phenomenon
- sudden loss of pharmacologic action
- abrupt onset of akinesia
- due to shortening of levodopa's 1/2 life in the striatum, without a measurable change in peripheral pharmacokinetics[4]
- the down-regulation of dopamine transporters that occurs in response to loss of dopaminergic terminals is mitigated by exogenous dopamine (from levodopa), thus the shorter duration of levodopa action[4]
- minimized by increasing the number or doses/day
- dark color of body fluids
- transient elevation of serum transaminases
Drug interactions
- pyridoxine (vitamin B6) enhances decarboxylation of L-dopa
- hydantoins decrease effect of L-dopa
- MAO inhibitor used in combination may result in hypertensive reactions
- carbidopa increases the concentration of L-dopa in the CNS by inhibiting peripheral decarboxylation
- antipsychotic agents (phenothiazines, haloperidol) & metoclopramide antagonize the effects of L-dopa
- benzodiazepines
- reserpine
- methyldopa
- antihypertensive agents
- antacids
Laboratory
Mechanism of action
- penetrates the CNS
- converted to dopamine in the basal ganglia
- increases dopamine concentrations in the CNS
More general terms
More specific terms
Additional terms
Component of
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998 - not on National VA formulary
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ 4.0 4.1 4.2 Troiano AR et al. PET demonstrates reduced dopamine transporter expression in PD with dyskinesias. Neurology 2009 Apr 7; 72:1211. PMID: https://www.ncbi.nlm.nih.gov/pubmed/19020294
Vingerhoets FJG. Dyskinesia in Parkinson disease: Back for the future? Neurology 2009 Apr 7; 72:1202. PMID: https://www.ncbi.nlm.nih.gov/pubmed/19349599 - ↑ 5.0 5.1 5.2 George J, FDA Approves Inhaled Levodopa for Parkinson's. Improved motor function when taken during 'off' episodes. MedPage Today. Dec. 26, 2018 https://www.medpagetoday.com/neurology/parkinsonsdisease/77104