TOLCAPONE

(tol'ca-pone)

Tasmar
Classifications: anticholinergic; catecholamine-o-methyltransferase (comt) inhibitor;
Therapeutic: anticholinergic; antiparkinson
Pregnancy Category: C

Availability

100 mg, 200 mg tablets

Action

Selective and reversible inhibitor of catecholamine-O-methyltransferase (COMT). COMT is the enzyme responsible for metabolizing catecholamines and, therefore, levodopa.

Therapeutic Effect

Concurrent administration of tolcapone and levodopa increases the amount of levodopa available to control Parkinson's disease by increasing dopaminergic brain stimulation.

Uses

Idiopathic Parkinson's disease as adjunct to levodopa/carbidopa.

Contraindications

Hypersensitivity to tolcapone; liver disease; pregnancy (category C); MAOI therapy.

Cautious Use

History of hypersensitivity to other COMT inhibitors (e.g., entacapone, nitecapone); anorexia nervosa; hematuria; hypotension; syncopy; renal disease; renal impairment; lactation.

Route & Dosage

Parkinson's Disease
Adult: PO 100 mg t.i.d. (max: 200 mg t.i.d.)

Administration

Oral

Give with food if GI upset occurs.
Give only in conjunction with levodopa/carbidopa therapy.
Note: Doses >100 mg t.i.d. are not recommended with moderate to severe liver impairment.
Store at 20°–25° C (68°–77° F) in a tightly closed container.

Adverse Effects (≥1%)

Body as a Whole: Muscle cramps, orthostatic complaints, fatigue, falling, balance difficulties, hyperkinesia, stiffness, arthritis, hypokinesia. CNS: Dyskinesia, sleep disorder, dystonia, excessive dreaming, somnolence, confusion, dizziness, headache, hallucination, syncope, paresthesias. CV: Chest pain, hypotension. GI: Nausea, anorexia, diarrhea, vomiting, constipation, fulminant liver failure, severe hepatocellular injury, dry mouth, abdominal pain, dyspepsia, flatulence. Respiratory: URI, dyspnea, sinus congestion. Skin: Sweating. Urogenital: UTI, urine discoloration, micturition disorder.

Interactions

Drug: Will increase levodopa levels when taken simultaneously; cns depressants may cause additive sedation; do not give with non-selective maois (isocarboxazid, phenelzine, or tranylcypromine furazolidone, linezolid, procarbazine).

Pharmacokinetics

Absorption: Rapidly absorbed from GI tract, bioavailability 65%; food decreases bioavailability. Peak: 2 h. Distribution: >99% protein bound. Metabolism: Extensively metabolized by COMT and glucuronidation. Elimination: 60% in urine, 40% in feces; clearance is reduced by 50% in patients with moderate cirrhotic liver disease. Half-Life: 2–3 h.

Nursing Implications

Assessment & Drug Effects

Lab tests: Monitor liver functions monthly for first 3 mo, every 6 wk for the next 3 mo, and periodically thereafter.
Monitor PT and INR carefully when given concurrently with warfarin.
Monitor carefully for and immediately report S&S of hepatic impairment (e.g., jaundice, dark urine).

Patient & Family Education

Do not engage in hazardous activities until response to drug is known. Avoid use of alcohol or sedative drugs while on tolcapone.
Rise slowly from a sitting or lying position to avoid a rapid drop in BP with possible weakness or fainting.
Nausea is a common possible adverse effect especially at the beginning of therapy.
Do not suddenly stop taking this drug. Doses must be gradually reduced over time.
Notify physician promptly about any of following: Increased loss of muscle control, fainting, yellowing of skin or eyes, darkening of urine, severe diarrhea, hallucinations.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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