Names and pronunciation
(lee-voe-doe′pa-kar-bi-doe′pa) Duopa, Sinemet, Rytary
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Drug reference
(lee-voe-doe′pa-kar-bi-doe′pa) Duopa, Sinemet, Rytary
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Func. class.: Antiparkinson agent
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Chem. class.: Catecholamine
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ACTION: Decarboxylation of levodopa in periphery is inhibited by carbidopa; more levodopa is made available for transport to the brain and for conversion to DOPamine in the brain
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USES: Parkinson’s disease, parkin- L sonism resulting from carbon monoxide, chronic manganese intoxication, cere- bral arteriosclerosis, motor fluctuations in those with advanced Parkinson’s disease
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Unlabeled uses: Restless legs syndrome
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CONTRAINDICATIONS: Hyper- sensitivity, malignant melanoma, history of malignant melanoma or undiagnosed skin lesions resembling melanoma Precautions: Pregnancy, breastfeeding, diabetes, closed-angle glaucoma, respi- ratory/cardiac/renal/hepatic disease, MI with dysrhythmias, seizures, peptic ulcer, depression
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SIDE EFFECTS CNS: Involuntary choreiform move- ments, hand tremors, fatigue, head- ache, anxiety, twitching, numbness, weakness, confusion, agitation, insomnia, nightmares, psychosis, hal- lucination, hypomania, severe depres- sion, dizziness, impulsive behaviors, neu roleptic malignant syndrome, suicidal ideation CV: Orthostatic hypotension, tachycar- dia, hypertension, palpitation, MI EENT: Blurred vision, diplopia, dilated pupils GI: Nausea, vomiting, anorexia, abdomi- nal distress, dry mouth, flatulence, dys- phagia, bitter taste, diarrhea, constipation, GI bleeding HEMA: Hemolytic anemia, leukopenia, agranulocytosis, thrombocytopenia INTEG: Rash, sweating, alopecia MISC: Urinary retention, incontinence, weight change, dark urine, increased libido, hypersensitivity, dark sweat
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INTERACTIONS Increase: hypertensive crisis—nonse lective MAOIs Increase: risk for sedation—CNS depressants Increase: hypotension—antihypertensives Increase: CV reactions—dobutamine, dopamine, epinephrine, isoproterenol, norepinephrine, TCAs Increase: effects of levodopa—antacids, metoclopramide Decrease: effects of levodopa—anticho- linergics, hydantoins, papaverine, pyri- doxine, benzodiazepines, antipsychotics Drug/Lab Test Increase: BUN, AST, ALT, bilirubin, alk phos, LDH, serum glucose Decrease: BUN, creatinine, uric acid False positive: urine ketones (dipstick), Coombs’ test False negative: urine glucose False increase: urine protein Drug/Food Decrease: absorption of levodopa—protein
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DOSAGE AND ROUTES Parkinson’s disease • Adult: PO (immediate-release tab- lets) 1 carbidopa 25 mg/levodopa 100- mg tablet tid, may increase by 1 tablet daily or every other day, max 8 tablets/ day Maintenance: At least 70-100 mg of carbidopa per day should be used Converting patients from levodopa to carbidopa-levodopa 25% of the previous dose of levodopa; usual dosage is 1 carbidopa 50 mg/ levodopa 200-mg ext-rel tablet bid For the treatment of restless legs syndrome (RLS) (unlabeled) • Adult: PO A bedtime dose starting at 25 mg/100 mg levodopa
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Available forms: Tabs 10 mg carbidopa/ 100 mg levodopa, 25 mg carbidopa/100 mg levodopa, 25 mg carbidopa/250 mg levodopa; ext rel tab 25 mg carbidopa/100 mg levodopa, 50 mg carbidopa/200 mg levodopa (Sinemet CR); oral disintegrating tab 10 mg carbidopa/100 mg levodopa, 25 mg carbidopa/100 mg levodopa, 25 mg carbidopa/250 mg levodopa; ext rel caps (Rytary) 23.75 mg/95 mg, 36.25 mg/145 mg, 48.75 mg/195 mg, 61.25 mg/245 mg; enteral suspension (Duopa) 20 mg/mL levodopa/4.63 mg/mL carbidopa
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Administer: • Pyridoxine (B6) not effective for re- versing Sinemet PO route • Do not crush or chew ext rel tabs; they may be broken in half; adjust dosage to response • Oral disintegrating tab by gently re- moving from bottle, placing on tongue and swallowing with saliva; after tab dis- solves, liquid is not necessary • With meals if GI symptoms occur; limit protein taken with product • Only after nonselective MAOIs have been discontinued for 2 wk; if patient has been previously treated with levodopa, discontinue for at least 12 hr before change to carbidopa- levodopa Enteral route • Fully thaw in refrigerator; remove 1 cas- sette from refrigerator 20 min before use, give through NG tube or a percutaneous endoscopic gastrostomy jejunostomy tube connected to the CADD-Legacy pump; dis- connect after use and flush with water; cassettes are single-use only, label in order to be used based on date
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Assess: • Parkinson’s symptoms: tremors, pill rolling, drooling, akinesia, rigidity; shuf- fling gait before, during treatment • B/P, respiration; orthostatic B/P • Mental status: affect, mood, behavioral changes, depression, complete suicide assessment • Toxicity: muscle twitching, blepharo spasm • Renal, hepatic, hematopoietic tests; also for diabetes, acromegaly if on long- term therapy • End-of-dose akinesia, on/off phenom enon; akinesia paradoxica • Pregnancy/breastfeeding: use only if benefits outweigh fetal risk; product is excreted in breast milk
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Evaluate: • Therapeutic response: decrease in akathisia/bradykinesis, tremor, rigidity, improved mood
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CLINICAL CONSIDERATIONS
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Patient and caregiver information: • To change positions slowly to prevent orthostatic hypotension, especially dur- ing beginning of treatment • That falling asleep when engaged in activities may occur • To report side effects: twitching, eye spasms because these indicate overdose • To use product as prescribed; not to double doses; if discontinued abruptly, parkinsonian crisis, neuroleptic malignant syndrome (NMS) may occur; to gradually taper • To use ODT immediately after remov- ing from container, to dissolve on tongue, swallow with saliva • That urine, sweat may darken • To use physical activities to maintain mobility, lessen spasms • To use with meals to decrease GI up- set; do not use high-protein meals • That improvement may not occur for 2-4 mo; about “on-off phenomenon” • Not to chew or crush extended-release product • To immediately report nausea, vomit ing, abdominal pain, ongoing constipation if using enteral product
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PHARMACOKINETICS PO: Onset 30 min, peak 1-3 hr, excreted in urine (metabolites) EXT REL: Onset 4-6 hr Enteral: Peak 2.5 hr
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• Adult: PO (immediate-release tab- lets) 1 carbidopa 25 mg/levodopa 100- mg tablet tid, may increase by 1 tablet daily or every other day, max 8 tablets/ day Maintenance: At least 70-100 mg of carbidopa per day should be used Converting patients from levodopa to carbidopa-levodopa 25% of the previous dose of levodopa; usual dosage is 1 carbidopa 50 mg/ levodopa 200-mg ext-rel tablet bid For the treatment of restless legs syndrome (RLS) (unlabeled)
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• Adult: PO A bedtime dose starting at 25 mg/100 mg levodopa
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