Isoproterenol

INDICATIONS AND USAGE Isoproterenol hydrochloride injection is indicated: For mild or transient episodes of heart block that do not require electric shock or pacemaker therapy. For serious episodes of heart block and Adams-Stokes attacks (except when caused by ventricular tachycardia or fibrillation). (See CONTRAINDICATIONS.) For use in cardiac arrest until electric shock or pacemaker therapy, the treatments of choice, is available. (See CONTRAINDICATIONS.) For bronchospasm occurring during anesthesia. As an adjunct to fluid and electrolyte replacement therapy and the use of other drugs and procedures in the treatment of hypovolemic and septic shock, low cardiac output (hypoperfusion) states, congestive heart failure, and cardiogenic shock. (See WARNINGS.)

DOSAGE AND ADMINISTRATION Start isoproterenol hydrochloride injection at the lowest recommended dose and increase the rate of administration gradually if necessary while carefully monitoring the patient. The usual route of administration is by intravenous infusion or bolus intravenous injection. In dire emergencies, the drug may be administered by intracardiac injection. If time is not of the utmost importance, initial therapy by intramuscular or subcutaneous injection is preferred. Recommended dosage for adults with heart block, Adams-Stokes attacks, and cardiac arrest : Route of Administration Preparation of Dilution Initial Dose Subsequent Dose Range* Bolus intravenous injection Dilute 1 mL (0.2 mg) in 9 mL of Sodium Chloride Injection, USP, or 5% Dextrose Injection, USP 0.02 mg to 0.06 mg (1 mL to 3 mL of diluted solution) 0.01 mg to 0.2 mg (0.5 mL to 10 mL of diluted solution) Intravenous infusion Dilute 10 mL (2 mg) in 500 mL of 5% Dextrose Injection, USP 5 mcg/min. (1.25 mL of diluted solution per minute) Intramuscular Use Solution undiluted 0.2 mg (1 mL) 0.02 mg to 1 mg (0.1 mL to 5 mL) Subcutaneous Use Solution undiluted 0.2 mg (1 mL) 0.15 mg to 0.2 mg (0.75 mL to 1 mL) Intracardiac Use Solution undiluted 0.02 mg (0.1 mL) * Subsequent dosage and method of administration depend on the ventricular rate and the rapidity with which the cardiac pacemaker can take over when the drug is gradually withdrawn. There are no well-controlled studies in children to establish appropriate dosing; however, the American Heart Association recommends an initial infusion rate of 0.1 mcg/kg/min, with the usual range being 0.1 mcg/kg/min to 1 mcg/kg/min. Recommended dosage for adults with shock and hypoperfusion states: Route of Administration Preparation of Dilution † Infusion Rate †† Intravenous infusion Dilute 5 mL (1 mg) in 500 mL of 5% Dextrose Injection, USP 0.5 mcg to 5 mcg per minute(0.25 mL to 2.5 mL of diluted solution) † Concentrations up to 10 times greater have been used when limitation of volume is essential. †† Rates over 30 mcg per minute have been used in advanced stages of shock. The rate of infusion should be adjusted on the basis of heart rate, central venous pressure, systemic blood pressure, and urine flow. If the heart rate exceeds 110 beats per minute, it may be advisable to decrease or temporarily discontinue the infusion. Recommended dosage for adults with bronchospasm occurring during anesthesia: Route of Administration Preparation of Dilution Initial Dose Subsequent Dose Bolus intravenous injection Dilute 1 mL (0.2 mg) in 9 mL of Sodium Chloride Injection, USP, or 5% Dextrose Injection, USP 0.01 mg to 0.02 mg (0.5 mL to 1 mL of diluted solution) The initial dose may be repeated when necessary Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Such solution should not be used.

WARNINGS AND PRECAUTIONS WARNINGS AND PRECAUTIONS • Cardiac arrhythmias and ischemia may be induced by Isoproterenol Hydrochloride Injection ( 5.1 ) • Sulfite: Isoproterenol Hydrochloride Injection contains metabisulfite, which may cause allergic reaction ( 5.2 ) 5.1 Cardiac Arrhythmias and Ischemia Isoproterenol may induce cardiac arrhythmias and myocardial ischemia in patients, especially patients with coronary artery disease, or cardiomyopathy. 5.2 Allergic Reactions associated with Sulfite Isoproterenol hydrochloride injection contains sodium metabisulfite, which may cause mild to severe allergic reactions including anaphylaxis or asthmatic episodes, particularly in patients with a history of allergies. However, the presence of metabisulfite in this product should not preclude its use for treatment in emergency situations, even if the patient is sulfite-sensitive, as the alternatives to using isoproterenol in a life-threatening situation may not be satisfactory.

CONTRAINDICATIONS Isoproterenol hydrochloride injection is contraindicated in patients with: • Tachycardia • Ventricular arrhythmias • Angina pectoris CONTRAINDICATIONS Isoproterenol hydrochloride injection is contraindicated in patients with: • Tachycardia ( 4 ) • Ventricular arrhythmias ( 4 ) • Angina pectoris ( 4 )

DRUG INTERACTIONS Table 1. Clinically Relevant Interactions with Isoproterenol Epinephrine Clinical Impact Both drugs are direct cardiac stimulants, and their combined effects may induce serious arrhythmias upon simultaneous administration. Intervention Isoproterenol hydrochloride injection and epinephrine should not be administered simultaneously. Drugs that may potentiate clinical response of Isoproterenol Clinical Impact The effects of isoproterenol may be potentiated by tricyclic antidepressants, monoamine oxidase inhibitors, levothyroxine sodium, and certain antihistamines, notably chlorpheniramine, tripelennamine, and diphenhydramine. Intervention Monitor hemodynamic parameters in patients who concurrently are taking tricyclic antidepressants, monoamine oxidase inhibitors, levothyroxine sodium and certain antihistamines. Adjust doses appropriately. Drugs that may reduce clinical response of Isoproterenol Clinical Impact The cardiostimulating and bronchodilating effects of isoproterenol are antagonized by beta-adrenergic blocking drugs, such as propranolol. Intervention Monitor for hemodynamic response and relief of bronchospasm and adjust dose appropriately. Do not administer isoproterenol hydrochloride injection and epinephrine simultaneously due to combined effects may induce serious arrhythmias. ( 7 ) Concomitant use of tricyclic antidepressants, monoamine oxidase inhibitors, levothyroxine sodium and certain antihistamines; hemodynamic parameters may potentiate a clinical response of isoproterenol. ( 7 ) Beta-adrenergic blocking drugs may reduce cardiostimulating and bronchodilating effects of isoproterenol. ( 7 ) See 17 for PATIENT COUNSELING INFORMATION.

ADVERSE REACTIONS The following adverse reactions have been associated with use of isoproterenol. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to estimate their frequency reliably or to establish a causal relationship to drug exposure. Nervous system disorders: Nervousness, headache, dizziness, visual blurring Cardiovascular: Tachycardia, tachyarrhythmias, palpitations, angina, ventricular arrhythmias, Adams-Stokes attacks, pulmonary edema Respiratory: Dyspnea Other: Flushing of the skin, sweating, mild tremors, pallor, nausea ADVERSE REACTIONS Common adverse reactions with isoproterenol include tachycardia and palpitations ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact KVK-Tech Inc at 1-800-862-3895 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

CLINICAL PHARMACOLOGY Isoproterenol is a potent nonselective beta-adrenergic agonist with very low affinity for alpha-adrenergic receptors. Intravenous infusion of isoproterenol in man lowers peripheral vascular resistance, primarily in skeletal muscle but also in renal and mesenteric vascular beds. Diastolic pressure falls. Renal blood flow is decreased in normotensive subjects but is increased markedly in shock. Systolic blood pressure may remain unchanged or rise, although mean arterial pressure typically falls. Cardiac output is increased because of the positive inotropic and chronotropic effects of the drug in the face of diminished peripheral vascular resistance. The cardiac effects of isoproterenol may lead to palpitations, sinus tachycardia, and more serious arrhythmias; large doses of isoproterenol may cause myocardial necrosis in animals. Isoproterenol relaxes almost all varieties of smooth muscle when the tone is high, but this action is most pronounced on bronchial and gastrointestinal smooth muscle. It prevents or relieves bronchoconstriction, but tolerance to this effect develops with overuse of the drug. In man, isoproterenol causes less hyperglycemia than does epinephrine. Isoproterenol and epinephrine are equally effective in stimulating the release of free fatty acids and energy production. Absorption, Fate, and Excretion. Isoproterenol is metabolized primarily in the liver and other tissues by COMT. Isoproterenol is a relatively poor substrate for MAO and is not taken up by sympathetic neurons to the same extent as are epinephrine and norepinephrine. The duration of action of isoproterenol may therefore be longer than that of epinephrine, but is still brief.