DUOPA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DUOPA (DUOPA).
DUOPA is a combination of carbidopa and levodopa. Levodopa is a precursor of dopamine that crosses the blood-brain barrier and is converted to dopamine in the brain, replenishing depleted dopamine stores in the striatum. Carbidopa inhibits peripheral decarboxylation of levodopa, increasing the availability of levodopa for transport to the brain.
| Metabolism | Levodopa is metabolized primarily by aromatic L-amino acid decarboxylase (AADC) and catechol-O-methyltransferase (COMT) in the peripheral tissues. Carbidopa inhibits peripheral AADC. |
| Excretion | Renal: carbidopa ~50% unchanged, levodopa minimal; fecal: ~30% of levodopa metabolites; biliary: minor |
| Half-life | Levodopa 1-2 h; carbidopa 1-2 h; clinical context: short t1/2 requires frequent dosing; extended-release formulation prolongs |
| Protein binding | Levodopa ~10% bound to albumin; carbidopa ~36% bound to albumin |
| Volume of Distribution | Levodopa 1.5-2 L/kg, indicating extensive tissue distribution; carbidopa 0.3-0.4 L/kg |
| Bioavailability | Oral: levodopa 70-80% with carbidopa (reduces peripheral metabolism); enteral suspension: ~99% absorbed |
| Onset of Action | Oral: levodopa 0.5-1 h; clinical effect within 1 h |
| Duration of Action | Oral: 4-6 h for immediate-release; longer with Duopa (carbidopa/levodopa enteral suspension) continuous infusion over 16 h |
| Molecular Weight | 197.19 |
| Action Class | Analgesic & Antipyretic-PCM |
| Brand Substitutes | Alice 650mg Tablet, Cofamol 650mg Tablet, Algina 650 Tablet, PUC 650 Tablet, Paracip 650 Tablet, Calpol 500mg Tablet, Dolo 500 Tablet, Pacimol 500 Tablet, T-98 Tablet, Parazex 500mg Tablet, Infemol 250mg/5ml Suspension, Chilmol 250mg/5ml Suspension, Pedmol 250mg/5ml Suspension, Unflem 250mg/5ml Suspension, Nicetamol 250mg/5ml Suspension, Flumol 125mg/5ml Suspension, Arden 125mg/5ml Suspension, Pinkbery 125mg/5ml Suspension, Polymol Suspension, Parpol 125mg/5ml Suspension |
One capsule orally, once daily at bedtime. Dose strengths available: 23.75 mg/9.5 mg (carbidopa/levodopa), 36.25 mg/14.5 mg, 48.75 mg/19.5 mg, 61.25 mg/24.5 mg. Titrate based on efficacy and tolerability; maximum dose 61.25 mg/24.5 mg.
| Dosage form | SUSPENSION |
| Renal impairment | No specific guidelines; use with caution in renal impairment. GFR <30 mL/min: not recommended due to lack of data. For GFR 30-60 mL/min: monitor for orthostatic hypotension and neuropsychiatric effects. |
| Liver impairment | Child-Pugh Class A or B: no adjustment needed. Child-Pugh Class C: not recommended (no data). |
| Pediatric use | Safety and efficacy not established in pediatric patients (<18 years). |
| Geriatric use | Elderly patients may require lower initial doses due to increased sensitivity. Start at lowest available strength (23.75 mg/9.5 mg) and titrate slowly. Monitor for hypotension, hallucinations, and dyskinesias. |
| 1st trimester | Insufficient human data; animal studies show risk. Carbidopa-levodopa should only be used during the first trimester if the potential benefit justifies the potential risk to the fetus. |
| 2nd trimester | Limited human data; based on animal studies and known pharmacodynamics, there is potential for fetal harm. Use only if clearly needed. |
| 3rd trimester | Use near term may cause adverse effects in the neonate (e.g., abnormal bone development, CNS effects). Use only if benefit outweighs risk. |
Clinical note
Comprehensive clinical and safety monograph for DUOPA (DUOPA).
| Placental transfer | Levodopa crosses the placenta; carbidopa has limited data but likely crosses due to its molecular weight and lipophilicity. |
| Breastfeeding | Levodopa is excreted into human breast milk in low concentrations. Carbidopa is also excreted but data are limited. The American Academy of Pediatrics considers levodopa compatible with breastfeeding. Monitor infant for potential side effects such as drowsiness or irritability. |
■ FDA Black Box Warning
None
| Serious Effects |
Narrow-angle glaucomaConcurrent use of nonselective MAO inhibitors (e.g., phenelzine, tranylcypromine)Known hypersensitivity to carbidopa or levodopaSuspicion of melanoma or undiagnosed skin lesions
| Precautions | May cause or exacerbate dyskinesia, Risk of falling asleep during daily activities, Risk of hypotension, especially orthostatic hypotension, May impair mental and/or physical abilities required for driving, Risk of melanoma; periodic skin examinations recommended, May cause hallucinations, psychosis, or impulse control disorders, May cause or worsen glaucoma; monitor intraocular pressure, Contains sulfites; may cause allergic reactions in susceptible individuals |
| Food/Dietary | High-protein meals can reduce levodopa absorption. Avoid large protein-rich meals close to dosing times. Iron supplements may reduce absorption and should be separated by at least 2 hours. Pyridoxine (vitamin B6) in high doses may antagonize levodopa effects; however, Duopa contains carbidopa, which inhibits this interaction, so modest dietary vitamin B6 is not a concern. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | DUOPA (carbidopa/levodopa enteral suspension) is Pregnancy Category C. First trimester: Limited human data; animal studies show fetal malformations at high doses. Second and third trimesters: May cause fetal harm; avoid unless benefit outweighs risk. Risk of fetal levodopa exposure unknown. |
| Fetal Monitoring | Monitor maternal blood pressure, dyskinesias, and psychiatric symptoms. Fetal monitoring: ultrasound for growth and development; consider non-stress test if maternal complications arise. Monitor for premature labor due to uterine contractions reported with levodopa. |
| Fertility Effects | Reproductive toxicity data limited. In animal studies, high-dose levodopa impaired fertility and caused estrous cycle disruption. Human effects on fertility unknown; may inhibit prolactin secretion, potentially affecting ovulation. |
| Clinical Pearls | Duopa (carbidopa/levodopa enteral suspension) is indicated for advanced Parkinson's disease with motor fluctuations. Administer via percutaneous endoscopic gastrostomy with jejunal tube (PEG-J). Morning dose is given as a bolus via pump, followed by continuous infusion. Must be refrigerated but brought to room temperature before use. Monitor for infusion site reactions and bowel obstruction. Avoid abrupt discontinuation to prevent neuroleptic malignant syndrome. |
| Patient Advice | Duopa is given continuously through a tube in your stomach to help control Parkinson's symptoms. · Do not stop the infusion suddenly; talk to your doctor if you need to discontinue. · Store unopened cassettes in the refrigerator; let them warm to room temperature before use. · Report any redness, swelling, or pain at the tube site, or signs of bowel obstruction like severe constipation or vomiting. · You may experience dark urine, saliva, or sweat; this is harmless. · Avoid high-protein meals as they may reduce levodopa absorption; take the morning dose separate from protein-containing food. · Do not drive or operate machinery until you know how Duopa affects you. |