ISOSORBIDE DINITRATE

ISOSORBIDE DINITRATE (eye-soe-sor'bide) Coronex , Dilatrate-SR, Iso-Bid, Isordil, Novosorbide  Classifications: nitrate vasodilator; Therapeutic: vasodilator; nitrate Prototype: Nitroglycerin Pregnancy Category: C

Availability

2.5 mg, 5 mg, 10 mg sublingual tablets; 5 mg, 10 mg chewable tablets; 5 mg, 10 mg, 20 mg, 30 mg, 40 mg tablets; 40 mg sustained release tablets, capsules

Action

Relaxes vascular smooth muscle with resulting vasodilation. Dilation of peripheral blood vessels tends to cause peripheral pooling of blood, decreased venous return to heart, and decreased left ventricular end-diastolic pressure, with consequent reduction in myocardial oxygen consumption.

Therapeutic Effect

Has an antianginal effect as a result of vasodilation of the coronary arteries.

Uses

Relief of acute anginal attacks and for management of long-term angina pectoris.

Unlabeled Uses

Alone or in combination with a cardiac glycoside or with other vasodilators (e.g., hydralazine, prazosin, for refractory CHF; diffuse esophageal spasm without gastroesophageal reflux and heart failure).

Contraindications

Hypersensitivity to nitrates or nitrites; severe anemia; head trauma; increased intracranial pressure; recent MI; GI disease; pregnancy (category C).

Cautious Use

Glaucoma, hypotension, hypovolemia; hyperthyroidism; hepatic disease; elderly; lactation.

Route & Dosage

Angina Prophylaxis Adult: PO Regular tablets 2.5–30 mg q.i.d. a.c. and h.s.; Sublingual tablet 2.5–10 mg q4–6h; Chewable tablet 5–30 mg chewed q2–3h; Sustained release tablets 40 mg q6–12h Acute Anginal Attack Adult: PO Sublingual tablet 2.5–10 mg q2–3h prn; Chewable tablet 5–30 mg chewed prn for relief

Administration

Oral

• Do not confuse with isosorbide, an oral osmotic diuretic.
• Give regular oral forms on an empty stomach (1 h a.c. or 2 h p.c.). If patient complains of vascular headache, however, it may be taken with meals.
• Advise patient not to eat, drink, talk, or smoke while sublingual tablet is under tongue.
• Instruct patient to place sublingual tablet under tongue at first sign of an anginal attack. If pain is not relieved, repeat dose at 5–10 min intervals to a maximum of 3 doses. If pain continues, notify physician or go to nearest hospital emergency room.
• Chewable tablet must be thoroughly chewed before swallowing.
• Do not crush sustained release form. It must be swallowed whole.
• Have patient sit when taking rapid-acting forms of isosorbide dinitrate (sublingual and chewable tablets) because of the possibility of faintness.
• Store in tightly closed container in a cool, dry place. Do not expose to extremes of temperature.

Adverse Effects (≥1%)

Body as a Whole: Hypersensitivity reaction, paradoxical increase in anginal pain, methemoglobinemia (overdose). CNS: Headache, dizziness, weakness, lightheadedness, restlessness. CV: Palpitation, postural hypotension, tachycardia. GI: Nausea, vomiting. Skin: Flushing, pallor, perspiration, rash, exfoliative dermatitis.

Interactions

Drug: Alcohol may enhance hypotensive effects and lead to cardiovascular collapse; antihypertensive agents, phenothiazines add to hypotensive effects.

Pharmacokinetics

Absorption: Significant first pass metabolism with PO absorption, with 10–90% reaching systemic circulation. Onset: 2–5 min SL; within 1 h regular tabs; within 3 min chewable tabs; 30 min sustained release tabs. Duration: 1–2 h SL; 4–6 h regular tabs; 0.5–2 h chewable tabs; 6–8 h sustained release tabs. Metabolism: In liver. Elimination: 80–100% in urine within 24 h.

Nursing Implications

Assessment & Drug Effects

• Monitor effectiveness of drug in relieving angina.
• Note: Headaches tend to decrease in intensity and frequency with continued therapy but may require administration of analgesic and reduction in dosage.
• Note: Chronic administration of large doses may produce tolerance and thus decrease effectiveness of nitrate preparations.

Patient & Family Education

• Make position changes slowly, particularly from recumbent to upright posture, and dangle feet and ankles before walking.
• Lie down at the first indication of light-headedness or faintness.
• Keep a record of anginal attacks and the number of sublingual tablets required to provide relief.
• Do not drink alcohol because it may increase possibility of light-headedness and faintness.

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