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02/11/2014 09:29AM
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carbidopa/levodopa (kar-bi-doe-pa/lee-voe-doe-pa)
Levocarb CR, Parcopa, Sinemet, Sinemet CR
Classification
Therapeutic: antiparkinson agents
Pharmacologic: dopamine agonists
Pregnancy Category C (carbidopa/levodopa)
Parkinson’s disease. Not useful for drug-induced extrapyramidal reactions.
Action
Levodopa is converted to dopamine in the CNS, where it serves as a neurotransmitter.
Carbidopa, a decarboxylase inhibitor, prevents peripheral destruction of levodopa.
Therapeutic Effects: Relief of tremor and rigidity in Parkinson’s syndrome.
Pharmacokinetics
Absorption: Well absorbed following oral administration.
Distribution: Widely distributed. Levodopa— enters the CNS in small concentrations. Carbidopa— does not cross the blood-brain barrier but does cross the placenta. Both enter breast milk.
Metabolism and Excretion: Levodopa— mostly metabolized by the GI tract
and liver. Carbidopa— 30% excreted unchanged by the kidneys.
Half-life: Levodopa— 1 hr; carbidopa— 1– 2 hr.
TIME/ACTION PROFILE (antiparkinson effects)
ROUTE
ONSET
PEAK
DURATION
Carbidopa
Levodopa
Carbidopa/levodopa
sustained release
unknown
10–15 min
unknown
unknown
unknown
2 hr
5–24 hr
5–24 hr or more
12 hr
Contraindications/Precautions
Contraindicated in: Hypersensitivity; Angle-closure glaucoma; MAO inhibitor
therapy; Malignant melanoma; Undiagnosed skin lesions; Some products contain tar⫽ Genetic Implication.
pg 1 # 1
trazine, phenylalanine, or aspartame and should be avoided in patients with known
hypersensitivity.
Use Cautiously in: History of cardiac, psychiatric, or ulcer disease; OB, Pedi:
Safety not established; Lactation: Maypserum prolactin.
Adverse Reactions/Side Effects
CNS: involuntary movements, anxiety, dizziness, hallucinations, memory loss, psychiatric problems, urges (gambling, sexual). EENT: blurred vision, mydriasis. GI:
nausea, vomiting, anorexia, dry mouth, hepatotoxicity. Derm: melanoma. Hemat:
hemolytic anemia, leukopenia. Misc: darkening of urine or sweat.
Indications
⫽ Canadian drug name.
Plate # 0-Composite
Interactions
Drug-Drug: Use with MAO inhibitors may result in hypertensive reactions.qrisk
of arrhythmias with inhalation hydrocarbon anesthetics (especially halothane;
if possible discontinue 6– 8 hr before anesthesia). Phenothiazines, haloperidol,
papaverine, phenytoin, and reserpine maypeffect of levodopa. Large doses of
pyridoxine maypbeneficial effects of levodopa. Concurrent use with methyldopa
may alter the effectiveness of levodopa andqrisk of CNS side effects.qhypotension
may result with concurrent antihypertensives. Anticholinergics maypabsorption of levodopa.qrisk of adverse reactions with selegilene or cocaine.
Drug-Natural Products: Kava-kava mayplevodopa effectiveness.
Drug-Food: Ingestion of foods containing large amounts of pyridoxine maypeffect of levodopa.
Route/Dosage
Carbidopa/Levodopa
PO (Adults): 25 mg carbidopa/100 mg levodopa 3 times daily; may beqevery 1– 2
days until desired effect is achieved (max ⫽ 8 tablets of 25 mg carbidopa/100 mg levodopa/day).
Carbidopa/Levodopa Extended-Release
PO (Adults): Patients not currently receiving levodopa— 50 mg carbidopa/200
mg levodopa twice daily (minimum of 6 hr apart) initially. Conversion from standard carbidopa/levodopa— initiate therapy with at least 10% more levodopa content/day (may need up to 30% more) given at 4– 8 hr intervals while awake. Allow 3
days between dosage changes; some patients may require larger doses and shorter
dosing intervals.
CAPITALS indicate life-threatening, underlines indicate most frequent.
Strikethrough ⫽ Discontinued.
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NURSING IMPLICATIONS
Assessment
● Assess parkinsonian symptoms (akinesia, rigidity, tremors, pill rolling, shuffling
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solve in seconds, then swallow with saliva. Administration with liquid is not necessary.
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gait, mask-like face, twisting motions, and drooling) during therapy. “On-off phenomenon” may cause symptoms to appear or improve suddenly.
Assess BP and pulse frequently during period of dose adjustment.
Lab Test Considerations: May cause false-positive test results in Coombs’ test.
May causeqserum glucose. Dipstick for urine ketones may reveal false-positive
results.
Monitor hepatic and renal function and CBC periodically in patients on long-term
therapy. May causeqAST, ALT, bilirubin, alkaline phosphatase, LDH, and serum
protein-bound iodine concentrations. May causepBUN, creatinine, and uric acid.
May causephemoglobin,phematocrit, agranulocytosis, hemolytic and nonhemolytic anemia, thrombocytopenia, leukopenia, andqWBC.
Toxicity and Overdose: Assess for signs of toxicity (involuntary muscle twitching, facial grimacing, spasmodic eye winking, exaggerated protrusion of tongue,
behavioral changes). Consult health care professional if symptoms occur.
Potential Nursing Diagnoses
Impaired physical mobility (Indications)
Risk for injury (Indications)
Implementation
Patient/Family Teaching
● Instruct patient to take.medication at regular intervals as directed. Do not change
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● Do not confuse Sinemet with Janumet.
● In the carbidopa/levodopa combination, the number following the drug name
represents the milligrams of each respective drug.
● In preoperative patients or patients who are NPO, confer with health care profes-
sional about continuing medication administration.
● PO: Administer on a regular schedule. Hospitalized patients should be continued
on same schedule as at home. Administer while awake, not around the clock to
improve sleep and prevent side effects.
● Controlled-release tablets may be administered as whole or half tablets, but they
should not be crushed or chewed.
● For orally disintegrating tablets, just prior to administration remove tablet from
bottle with dry hands. Immediately place tablet on top of tongue. Tablet will dis-
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dose regimen or take additional antiparkinson drugs, including more carbidopa/
levodopa, without consulting health care professional. Take missed doses as soon
as remembered, unless next scheduled dose is within 2 hr; do not double doses.
Explain that gastric irritation may be decreased by eating food shortly after taking
medications but that high-protein meals may impair levodopa’s effects. Dividing
the daily protein intake among all the meals may help ensure adequate protein intake and drug effectiveness. Do not drastically alter diet during carbidopa/levodopa therapy without consulting health care professional.
May cause sudden onset of sleep, drowsiness, or dizziness. Advise patient to avoid
driving and other activities that require alertness until response to drug is known.
Caution patient to change positions slowly to minimize orthostatic hypotension.
Health care professional should be notified if orthostatic hypotension occurs.
Instruct patient that frequent rinsing of mouth, good oral hygiene, and sugarless
gum or candy may decrease dry mouth.
Caution patient to monitor skin lesions for any changes. Health care professional
should be notified promptly because carbidopa/levodopa may activate malignant
melanoma.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional
before taking other medications, especially cold remedies. Large amounts of vitamin B6 (pyridoxine) and iron may interfere with the action of levodopa.
Inform patient that harmless darkening of saliva, urine, or sweat may occur.
Advise patient to notify health care professional if palpitations, urinary retention,
involuntary movements, behavioral changes, severe nausea and vomiting, new
skin lesions, or new or increased gambling, sexual, or other intense urges occur.
Dose reduction may be required.
Inform patient that sometimes a “wearing-off” effect may occur at end of dosing
interval. Notify health care professional if this poses a problem to lifestyle.
Advise female patients to notify health care professional if pregnancy is planned or
suspected or if breast feeding.
䉷 2015 F.A. Davis Company
CONTINUED
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CONTINUED
carbidopa/levodopa
Evaluation/Desired Outcomes
● Resolution of parkinsonian signs and symptoms. Therapeutic effects usually be-
come evident after 2– 3 wk of therapy but may require up to 6 mo. Patients who
take this medication for several yr may experience a decrease in the effectiveness
of this drug.
Why was this drug prescribed for your patient?
⫽ Canadian drug name.
⫽ Genetic Implication.
CAPITALS indicate life-threatening, underlines indicate most frequent.
Strikethrough ⫽ Discontinued.