propafenone hydrochloride

propafenone hydrochloride

Arythmol (UK), Rythmol

Pharmacologic class: Direct membrane stabilizer

Therapeutic class: Antiarrhythmic (class IC)

Pregnancy risk category C

FDA Boxed Warning

• In study of patients with asymptomatic, non-life-threatening ventricular arrhythmias who'd had myocardial infarctions more than 6 days but less than 2 years previously, excessive mortality or nonfatal cardiac arrest rate occurred in those treated with encainide or flecainide, compared with patients in carefully matched placebo groups. Given drug's known proarrhythmic properties and lack of evidence of improved survival for any antiarrhythmic in patients without life-threatening arrhythmias, reserve drug for patients with life-threatening ventricular arrhythmias.

Action

Slows conduction velocity in atrioventricular (AV) node, decreases automaticity, and increases ratio of effective refractory period to action potential duration; also has mild beta-adrenergic blocking properties

Availability

Tablets: 150 mg, 225 mg, 300 mg

⊘Indications and dosages

➣ Life-threatening ventricular arrhythmias; paroxysmal atrial fibrillation or flutter; paroxysmal supraventricular tachycardia

Adults: Dosage highly individualized based on response and tolerance. Initially, 150 mg P.O. q 8 hours (450 mg/day); may increase after 3 to 4 days to 225 mg P.O. q 8 hours (675 mg/day) or, if necessary, up to 300 mg P.O. q 8 hours (900 mg/day). Don't exceed 900 mg/day P.O.

Dosage adjustment

• Hepatic disease
• Supraventricular tachycardia, arrhythmias associated with Wolff-Parkinson-White syndrome
• Elderly patients

Contraindications

• Hypersensitivity to drug
• Sick-sinus syndrome, sinoatrial or AV block (unless patient has artificial pacemaker)
• Cardiogenic shock
• Bradycardia
• Uncontrolled heart failure
• Marked hypotension
• Bronchospastic disorders
• Electrolyte imbalances

Precautions

Use cautiously in:
• hepatic or renal impairment, myasthenia gravis
• pregnant or breastfeeding patients
• children.

Administration

• Give with food (but not with grapefruit juice) in three divided doses daily, once every 8 hours.

Route	Onset	Peak	Duration
P.O.	Variable	3.5 hr	Unknown

Adverse reactions

CNS: headache, dizziness, drowsiness, syncope, vertigo, confusion, asthenia, speech disturbances, memory loss, ataxia, paresthesia, anxiety, abnormal dreams, insomnia, tremor

CV: palpitations, angina, chest pain, hypotension, bradycardia, premature ventricular contractions, first-degree AV block, supraventricular or ventricular arrhythmias, heart failure, atrial fibrillation, intraventricular conduction delay

EENT: blurred vision, tinnitus

GI: nausea, vomiting, diarrhea, constipation, dyspepsia, abdominal pain or cramps, flatulence, dry mouth, anorexia

GU: reversible disorders of spermatogenesis

Hematologic: purpura, hemolytic anemia, leukopenia, agranulocytosis, thrombocytopenia, neutropenia

Hepatic: cholestasis, abnormal hepatic function

Musculoskeletal: muscle weakness, myalgia, leg cramps, myasthenia gravis exacerbation

Respiratory: dyspnea

Skin: rash, alopecia, diaphoresis

Other: altered taste, edema

Interactions

Drug-drug. Beta-adrenergic blockers: increased blood level and effects of beta-adrenergic blockers metabolized by liver

Cimetidine: increased propafenone blood level

Cyclosporine, desipramine, digoxin, theophylline, warfarin: increased blood levels of these drugs

Quinidine: delayed propafenone metabolism

Rifampin: decreased blood level and antiarrhythmic efficacy of propafenone

Drug-diagnostic tests. Antinuclear antibody: positive titer

Bleeding time: prolonged

Creatine kinase, glucose: increased levels

Granulocytes, white blood cells: decreased counts

Drug-herbs. Aloe, buckthorn, cascara sagrada, senna pod or leaf: increased antiarrhythmic action, decreased potassium level

Patient monitoring

• Monitor ECG and vital signs.
• Evaluate neurologic status. Stay alert for decreasing level of consciousness.
☞ Monitor CBC and liver function tests. Watch for evidence of blood dyscrasias and abnormal hepatic function.
• Monitor respiratory status for dyspnea.

Patient teaching

☞ Tell patient which cardiac, neurologic, and respiratory adverse effects to report immediately.
☞ Instruct patient to immediately report unusual bleeding or bruising.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.