Names and pronunciation
Imdur
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Drug reference
Imdur
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Func. class.: Antianginal, vasodilator
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Chem. class.: Nitrate
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Do not confuse: Isordil/Plendil
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ACTION: Relaxation of vascular smooth muscle, which leads to decreased preload, afterload, which is responsible for decreasing left ventricular end-diastolic pressure, systemic vascular resistance, and reducing cardiac oxygen demand
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USES: Treatment, prevention of chronic stable angina pectoris
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Unlabeled uses: Heart failure (dinitrate), esophageal spasms without GERD
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CONTRAINDICATIONS: Hyper- sensitivity to this product or nitrates; severe anemia, closed-angle glaucoma Precautions: Pregnancy, breastfeeding, children, orthostatic hypotension, MI, HF, severe renal/hepatic disease, increased intracranial pressure, cerebral hemorrhage, acute MI, geriatric patients, GI disease, syncope
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SIDE EFFECTS CNS: Vascular headache, flushing, diz ziness, weakness CV: Orthostatic hypotension, tachycar- dia, collapse, syncope GI: Nausea, vomiting INTEG: Pallor, sweating, rash MISC: Twitching, hemolytic anemia, met hemoglobinemia, tolerance, xerostomia
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INTERACTIONS • Fatal hypotension: avanafil, sildenafil, tadalafil, vardenafil; do not use together hypotension—β-blockers, Increase: diuretics, antihypertensives, alcohol, cal- cium channel blockers, phenothiazines Increase: heart rate, B/P—sympathomi- metics Increase: myocardial ischemia—rosiglit azone; avoid concurrent use
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DOSAGE AND ROUTES Dinitrate • Adult: PO 5-20 mg bid-tid initially, maintenance 10-40 mg bid-tid; EXT REL 40-80 mg q8-12hr, max 160 mg/day Mononitrate • Adult: PO (tablets) 10-20 mg bid, 7 hr apart; (extended release) initiate at 30-60 mg/day as a single dose, increase q3days as needed, may increase to 120 mg/day, max 240 mg/day
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Available forms: Dinitrate: ext rel tabs 40 mg; tabs 5, 10, 20, 30, 40 mg; mononitrate: tabs 10, 20 mg; ext rel 30, 60, 120 mg
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Administer: • Do not break, crush, or chew extended- release capsules • After checking expiration date • PO with 8 oz water on empty stomach • Extended release capsule/tablet: allow dosing interval >18 hr
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Assess: • Anginal pain: duration, time started, activity being performed, character • Methemoglobinemia (rare): cyanosis of lips, nausea/vomiting, coma, shock; usually caused by high dose of product but may occur with normal dosing • B/P, pulse, respirations during begin- ning therapy and periodically thereafter • Tolerance if taken over long period; to prevent, allow intervals of 12-14 hr/day without product • Headache, light-headedness, decreased B/P; may indicate a need for decreased dosage, treat headache with OTC analgesics • Beers: use with caution in older adults; may exacerbate episodes of syncope • Pregnancy/breastfeeding: use only if benefit outweighs fetal risk; cautious use in breastfeeding, excretion unknown
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Evaluate: • Therapeutic response: decrease or prevention of anginal pain
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CLINICAL CONSIDERATIONS
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Patient and caregiver information: • To leave tabs in original container • To avoid alcohol, OTC products unless approved by prescriber • That product may cause headache; that taking with meals may reduce or elimi- nate headache; to take no later than 7 PM (last dose) • To avoid hazardous activities if dizzi- ness occurs • About the importance of complying with complete medical regimen • To make position changes slowly to prevent orthostatic hypotension • Not to use with avanafil, sildenafil, tadalafil, vardenafil with nitrates; may cause serious drop in B/P • Not to discontinue abruptly, may cause heart attack • To use at beginning of angina symp toms, may repeat every 15 min; if no relief, seek medical attention immedi ately
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PHARMACOKINETICS Dinitrate Metabolized by liver, excreted in urine as metabolites (80%-100%) PO: Onset 15-30 min, duration 4-6 hr, half-life 5-6 hr SUS REL: Onset ≤4 hr, duration 6-8 hr Mononitrate SUS REL: Onset 30-60 min, peak 1-4 hr, duration 6-8 hr, half-life 5 hr
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• Adult: PO 5-20 mg bid-tid initially, maintenance 10-40 mg bid-tid; EXT REL 40-80 mg q8-12hr, max 160 mg/day Mononitrate
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• Adult: PO (tablets) 10-20 mg bid, 7 hr apart; (extended release) initiate at 30-60 mg/day as a single dose, increase q3days as needed, may increase to 120 mg/day, max 240 mg/day
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