Nitroglycerin (rectal)

7 DRUG INTERACTIONS PDE5 inhibitors: potentiation of hypotensive effects of organic nitrates; concomitant use is contraindicated. ( 4.1 , 7.1 ) Antihypertensives: possible additive hypotensive effects. ( 7.2 ) Aspirin: increased nitroglycerin levels. ( 7.3 ) Tissue-type Plasminogen Activator (t-PA): decreased thrombolytic effect. ( 7.4 ) Heparin: anticoagulant effect of heparin may be reduced. Monitor APTT. ( 7.5 ) Ergotamine: increased bioavailability of ergotamine. ( 7.6 ) Alcohol: Additive vasodilatory effects to nitroglycerin. Consumption of alcohol should be avoided. ( 7.7 )

7.1 PDE5 inhibitors Phosphodiesterase type 5 (PDE5) inhibitors such as sildenafil, vardenafil, and tadalafil have been shown to potentiate the hypotensive effects of organic nitrates. The time course of the interaction appears to be related to the half-life of the PDE5 inhibitor, however, the dose dependence of this interaction has not been studied. Use of RECTIV within a few days of PDE5 inhibitors is contraindicated.

7.2 Antihypertensives Patients receiving antihypertensive drugs, beta-adrenergic blockers, and other nitrates should be observed for possible additive hypotensive effects when using RECTIV. Marked orthostatic hypotension has been reported when calcium channel blockers and organic nitrates were used concomitantly. Beta-blockers blunt the reflex tachycardia produced by nitroglycerin without preventing its hypotensive effects. If beta-blockers are used with RECTIV in patients with angina pectoris, additional hypotensive effects may occur.

7.3 Aspirin Coadministration of aspirin (at doses between 500 mg and 1000 mg) and nitroglycerin has been reported to result in increased nitroglycerin maximum concentrations by as much as 67% and AUC by 73% when administered as a single dose. The pharmacological effects of RECTIV may be enhanced by concomitant administration of aspirin.

7.4 Tissue-type Plasminogen Activator (t-PA) Intravenous administration of nitroglycerin decreases the thrombolytic effect of tissue-type plasminogen activator (t-PA). Plasma levels of t-PA are reduced when coadministered with nitroglycerin. Therefore, caution should be observed in patients receiving RECTIV during t-PA therapy.

7.5 Heparin Although an interaction has been reported between intravenous heparin and intravenous nitroglycerin (resulting in a decrease in the anticoagulant effect of heparin), the data are not consistent. If patients are to receive intravenous heparin and RECTIV concurrently, the anticoagulation status of the patient must be checked.

7.6 Ergotamine Oral administration of nitroglycerin markedly decreases the first-pass metabolism of dihydroergotamine and consequently increases its oral bioavailability. Ergotamine is known to precipitate angina pectoris. Therefore the possibility of ergotism in patients receiving RECTIV should be considered.

7.7 Alcohol The vasodilating effects of nitroglycerin have been shown to be additive to the effects observed with alcohol.

8.1 Pregnancy Risk Summary There are no data on the use of nitroglycerin ointment intra-anally during pregnancy to determine a drug-associated risk of major birth defects, miscarriage or other adverse maternal or fetal outcomes. In animal reproduction studies, no malformations were observed in offspring of pregnant rats and rabbits administered nitroglycerin by topical or dietary route during the period of organogenesis (see Data). The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S.

general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Data Animal Data Animal reproduction studies in rats and rabbits were conducted with topically applied nitroglycerin ointment at doses up to 80 mg/kg/day and 240 mg/kg/day, respectively. No toxic effects on dams or fetuses were seen at any dose tested. An animal reproduction study was conducted in rats with nitroglycerin administered in the diet at levels up to 1% content (approximately 430 mg/kg/day) on days 6 to 15 of gestation.

In offspring of the high-dose group, an increased but not statistically significant incidence of diaphragmatic hernias was noted together with decreased hyoid bone ossification. The latter finding probably reflects delayed development, thus indicating no clear evidence of a potential teratogenic effect of nitroglycerin.