"Troy Brown, RN
Medscape Medical News
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Mechanism of Action
Nitroglycerin forms free radical nitric oxide (NO), which activates guanylate cyclase, resulting in an increase of guanosine 3',5'-monophosphate (cyclic GMP) in smooth muscle and other tissues. This leads to dephosphorylation of myosin light chains, which regulates the contractile state in smooth muscle and results in vasodilatation.
The principal pharmacological action of nitroglycerin is relaxation of vascular smooth muscle. Intra-anal application of nitroglycerin reduces sphincter tone and resting intra-anal pressure.
Absorption: In six healthy subjects, the average absolute bioavailability of nitroglycerin applied to the anal canal as a 0.2% w/w ointment was approximately 50% of the 0.75 mg nitroglycerin dose.
Distribution: The volume of distribution of nitroglycerin following intravenous administration is about 3 L/kg. At plasma concentrations between 50 and 500 ng/mL, the binding of nitroglycerin to plasma proteins is approximately 60%, while that of 1,2- and 1,3-dinitroglycerin is 60% and 30%, respectively.
Metabolism: Nitroglycerin is metabolized by a liver reductase enzyme to glycerol di- and mononitrate metabolites and ultimately to glycerol and organic nitrate. Known sites of extrahepatic metabolism include red blood cells and vascular walls. In addition to nitroglycerin, the two major metabolites, 1,2- and 1,3- dinitroglycerols are found in plasma. The contribution of metabolites to the relaxation of the internal anal sphincter is unknown. The dinitrates are further metabolized to nonvasoactive mononitrates and ultimately to glycerol and carbon dioxide.
Elimination: Metabolism is the primary route of drug elimination. Nitroglycerin plasma concentrations decrease rapidly with a mean elimination half-life of two to three minutes. Half-life values range from 1.5 to 7.5 minutes. Clearance (13.6 L/min) greatly exceeds hepatic blood flow.
RECTIV ointment was evaluated in a 3-week double-blind, randomized, multi-center, placebo-controlled study. Patients with a painful chronic anal fissure for at least 6 weeks and moderate or severe pain prior to treatment ( ≥ 50 mm on the 100mm visual analog scale, VAS) were randomized to receive 0.4% (1.5mg) nitroglycerin or placebo ointment applied to the anal canal every 12 hours. Pain as assessed by the change in VAS from baseline to Days 14-18 was lower in patients receiving 0.4% ointment compared to placebo. The mean change from baseline was 44mm for RECTIV and 37mm for placebo. The difference in the mean change in pain between RECTIV and placebo was -7.0mm (95% Confidence Interval: -13.6 to -0.4mm).
Last reviewed on RxList: 8/2/2011
This monograph has been modified to include the generic and brand name in many instances.
Additional Rectiv Information
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