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Glyceryl Trinitrate - page 1
Keywords: GTN, Glyceryl trinitrate, Nutrition and Energy
By Einstein10 on 30/12/2009
Level: Foundation Degree
Page Number: 1 of 6 pages: 1 2 3 4 5 6
Title: Introduction to Pharmacokinetics and the factors affecting pharmacokinetic processes
1) Briefly explain why there are a number of different formulations of glyceryl trinitrate and compare the onset and duration of action from a sublingual tablet and Transdermal patch
Nitroglycerin (GTN), also known as glyceryl trinitrate is a nitric oxide donor commonly prescribed for the therapy of myocardial ischaemia, congestive heart failure, angina pectoris and pulmonary hypertension. It works by decreasing cardiac oxygen demand by reducing left ventricular pressure and systemic vascular resistance, and thereby dilating coronary arteries which improves collateral blood flow to the ischemic region/s.
The duration of GTN action is greatly depends on metabolism, not only by first-pass metabolism in the liver by the action of glutathione-nitrate reductase but also by extra hepatic tissues such as blood vessels.
Why there are a number of different formulations of glyceryl trinitrate
GTN can be administered by a number of routes and formulations’. These include; Sublingual tablet, Lingual spray, Buccal tablet, Sustained release, Topical ointments, Aerosol sprays Transdermal patches and intravenous administration. Table 1 summarises the different formulations and their effects, and shows that onset and duration of action depends on formulation.
Table 1
Glyceryl trinitrate (GTN)
Formulation Onset of Effect (min) Peak Effect (min) Lasting Duration
Sublingual tablet 1-3 4-8 30-60 min
Lingual spray 2 4-10 30-60 min
Buccal tablet 2-5 4-10 2 Hours
Sustained release 20-45 45-120 4-8 Hours
Topical 15-60 30-120 2-12 Hours
Transdermal patch 40-60 60-180 8-24 Hours
I.V Drip Immediate Immediate 3-5 min
Having various formulations of GTN can be very advantageous because firstly, it increases the options of administrating the drug via a number of routes and secondly, the formulations can be tailored from patient to patient. Depending on the severity of the situation and taking into account the patient’s medical history GTN can be administered for immediate relief in the case of an angina attack or prolonged use for acute angina. For acute angina attacks’ that have already begun, an immediate-acting formulation is required. In contrast, preventative therapy requires a long lasting formulation with more emphasis on duration and little emphasis on onset. The formulations used in immediate relief usually are in small doses, modified to last a few minutes or under an hour. Formulations for prolonged use are usually of higher doses and have a longer duration of action.
If the patient has a history of angina or myocardial infarction they will usually be prescribed a sublingual tablet, lingual spray or buccal tablet for personal use in case of an emergency as there may not be enough time to wait for an ambulance. These formulations are administered to avoid
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