Medical term:

COMT


COMT

Catechol-O-methyltransferase, an enzyme that breaks down dopamine and l-dopa in the brain and thus reduces the effectiveness of some treatments for Parkinson's disease. Drugs that inhibit COMT improve patient responsiveness to treatment with levodopa, one of the mainstays of treatment for Parkinson's disease.
Medical Dictionary, © 2009 Farlex and Partners

entacapone

Comtan, Comtess (UK)

Pharmacologic class: Catechol O-methyltransferase (COMT) inhibitor

Therapeutic class: Antidyskinetic

Pregnancy risk category C

Action

Inhibits COMT, the primary enzyme involved in metabolizing levodopa. This inhibition increases levodopa blood level and duration of action, easing symptoms of Parkinson's disease.

Availability

Tablets: 200 mg

Indications and dosages

➣ Adjunctive treatment of idiopathic Parkinson's disease in patients experiencing wearing off of carbidopa-levodopa effects

Adults: 200 mg P.O. with each carbidopa-levodopa dose, to a maximum of eight times daily (1,600 mg)

Contraindications

• Hypersensitivity to drug

Precautions

Use cautiously in:

• hepatic or renal dysfunction, hypertension, heart disease

• pregnant and breastfeeding patients.

Administration

• Give without regard to food.

• Administer at same time as carbidopa-levodopa. Make sure patient swallows tablet whole.

☞ Don't withdraw drug abruptly.

Adverse reactions

CNS: dizziness, depression, drowsiness, disorientation, memory loss, agitation, delusions, hallucinations, paranoia, euphoria, dyskinesia, hyperkinesia, light-headedness, paresthesia, heaviness of limbs, numbness of fingers

CV: tachycardia, orthostatic hypotension, hypertension

GI: nausea, vomiting, epigastric pain, flatulence

GU: urine discoloration

Respiratory: upper respiratory tract infection, dyspnea, sinus congestion

Other: fever

Interactions

Drug-drug. Ampicillin, chloramphenicol, cholestyramine, erythromycin, probenecid, rifampin: decreased entacapone excretion

Bitolterol, dobutamine, dopamine, epinephrine, isoetherine, isoproterenol, methyldopa, norepinephrine: increased heart rate, increased risk of arrhythmias, excessive blood pressure changes

MAO inhibitors: increased risk of toxicity

Drug-behaviors. Alcohol use: increased risk of adverse reactions

Patient monitoring

• Monitor vital signs, watching especially for orthostatic hypotension.

• Evaluate neurologic status closely. Check for hallucinations and new onset or exacerbation of dyskinesia.

• Assess respiratory status, particularly for dyspnea and signs and symptoms of upper respiratory tract infection.

• Monitor nutritional and hydration status if patient experiences vomiting.

Patient teaching

• Instruct patient to swallow tablet whole and to take it at same time as carbidopa-levodopa.

☞ Caution patient not to stop taking drug abruptly.

• Advise patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.

• Caution patient to avoid driving and other hazardous activities until drug no longer affects concentration and alertness.

☞ Instruct patient (and caregiver) to institute safety measures at home to prevent injury related to disease or drug's adverse CNS effects.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and behaviors mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved

entacapone

(en-tak-a-pone) ,

Comtan

(trade name)

Classification

Therapeutic: antiparkinson agents
Pharmacologic: catechol o methyltransferase inhibitors
Pregnancy Category: C

Indications

With levodopa/carbidopa to treat idiopathic Parkinson’s disease when signs and symptoms of end-of-dose "wearing-off" (so-called fluctuating patients) occur.

Action

Acts as a selective and reversible inhibitor of the enzyme catechol O-methyltransferase (COMT).
Inhibition of this enzyme prevents the breakdown of levodopa, increasing availability to the CNS.

Therapeutic effects

Prolongs duration of response to levodopa with end-of-dose motor fluctuations.
Decreased signs and symptoms of Parkinson’s disease.

Pharmacokinetics

Absorption: 35% absorbed following oral administration; absorption is rapid.
Distribution: Unknown.
Protein Binding: 98%.
Metabolism and Excretion: Minimal amounts excreted unchanged; highly metabolized followed by biliary excretion.
Half-life: Initial phase—0.4–0.7 hr; second phase—2.4 hr.

Time/action profile (inhibition of COMT)

ROUTEONSETPEAKDURATION
POunknownunknownup to 8 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity;Concurrent nonselective MAO inhibitor therapy.
Use Cautiously in: Hepatic impairment;Concurrent use of drugs that are metabolized by COMT; Obstetric / Lactation: Safety not established; Pediatric: No identified use in children.

Adverse Reactions/Side Effects

Central nervous system

  • neuroleptic malignant syndrome (life-threatening)
  • dizziness
  • hallucinations
  • syncope
  • urges (gambling, sexual)

Respiratory

  • pulmonary infiltrates
  • pleural effusion
  • pleural thickening

Cardiovascular

  • hypotension

Dermatologic

  • melanoma

Gastrointestinal

  • abdominal pain
  • colitis
  • diarrhea
  • nausea (during initiation)
  • retroperitoneal fibrosis

Genitourinary

  • brownish-orange discoloration of urine

Musculoskeletal

  • rhabdomyolysis (life-threatening)

Neurologic

  • dyskinesia

Interactions

Drug-Drug interaction

Concurrent use with selective MAO inhibitors is not recommended; both agents inhibit the metabolic pathways of catecholamines.Concurrent use of drugs that are metabolized by COMT such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, and methyldopa may ↑ risk of tachycardia, ↑ BP, and arrhythmias.Probenecid, cholestyramine, erythromycin, rifampin, ampicillin, and chloramphenicol may interfere with biliary elimination of entacapone; use concurrently with caution.

Route/Dosage

Oral (Adults) 200 mg with each dose of levodopa/carbidopa up to a maximum of 8 times daily.

Availability (generic available)

Tablets: 200 mg
In combination with: levodopa/carbidopa (Stalevo), see combination drugs.

Nursing implications

Nursing assessment

  • Assess parkinsonian and extrapyramidal symptoms (restlessness or desire to keep moving, rigidity, tremors, pill rolling, mask-like face, shuffling gait, muscle spasms, twisting motions, difficulty speaking or swallowing, loss of balance control) prior to and during therapy. Dyskinesia may increase with therapy.
  • Monitor patient for development of diarrhea. Usually occurs within 4 to 12 wk of start of therapy, but may occur as early as the first week and as late as months after initiation of therapy.
  • Monitor patient for signs similar to neuroleptic malignant syndrome (elevated temperature, muscular rigidity, altered consciousness, elevated CPK). Symptoms have been associated with rapid dose reduction or withdrawal of other dopaminergic drugs. Withdrawal should be gradual.

Potential Nursing Diagnoses

Impaired physical mobility (Indications)
Risk for injury (Indications)

Implementation

  • Oral: Always administer entacapone with levodopa/carbidopa. Entacapone has no antiparkinsonism effects of its own.

Patient/Family Teaching

  • Encourage patient to take entacapone as directed. Take missed doses as soon as possible, up to 2 hr before the next dose. Taper gradually when discontinuing or a withdrawal reaction may occur.
  • May cause dizziness or hallucinations. Advise patient to avoid driving or other activities that require alertness until response to the drug is known.
  • Inform patient that nausea may occur, especially at initiation of therapy and diarrhea. Advise patient with diarrhea to drink fluids to maintain adequate hydration and monitor for weight loss. If diarrhea is prolonged, may resolve with discontinuation. Therapy may cause change in urine color to brownish orange.
  • Caution patient to change positions slowly to minimize orthostatic hypotension.
  • Advise patient to notify health care professional if suspicious or unusual skin changes, hallucinations, or new or increased gambling, sexual, or other intense urges occur.
  • Instruct patient to notify health care professional if pregnancy is planned or suspected, or if breast feeding.
  • Emphasize the importance of routine follow-up exams.

Evaluation/Desired Outcomes

  • Decreased signs and symptoms of Parkinson’s disease.
Drug Guide, © 2015 Farlex and Partners

entacapone

A nitrocatechol-class COMT (catechol-O-methyltransferase) inhibitor used to improve motor performance in Parkinson patients receiving l-DOPA/carbidopa.

Adverse effects
Dyskinesia, which often resolves with ongoing therapy; diarrhoea, nausea and abdominal pain; asymptomatic red-brown urine.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

Comtan®

Entacapone Neurology A COMT inhibitor which may improve motor performance in Parkinson Pts receiving levodopa/carbidopa. See Parkinson's disease.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

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