Products
Nitroglycerin is commercially available in many countries in the form of chewable capsules (Nitroglycerin Streuli). The active ingredient was produced and used medicinally as early as the 19th century.
Structure and properties
Nitroglycerin or glycerol trinitrate (GTN, C3H5N3O9, Mr = 227.1 g/mol) is an organic nitrate. It is nitrated glycerol. Nitroglycerin exists as an oily liquid and is explosive unless stabilized with suitable excipients.
Synthesis
Effects
Nitroglycerin (ATC C01DA02) has vasodilator, antihypertensive, antianginal, and antispasmodic properties. It relaxes vascular smooth muscle as well as smooth muscle of the bronchi, urinary tract, gallbladder, bile duct, esophagus, and intestines. Nitrates are prodrugs with high first-pass metabolism. The effects are due to the release of nitric oxide (NO), which relaxes smooth muscle. NO stimulates guanylate cyclase and increases the intracellular concentration of cyclic guanosine monophosphate (cGMP). Nitrates are active on veins, arterioles, arteries, and coronary arteries and mediate the following effects:
- Dilatation of blood vessels; at low doses, this is primarily veins, but at higher doses, it is also arteries
- Lowering blood pressure
- Reduction of preload, reduction of blood return to the heart.
- Reduction of oxygen consumption of the heart muscle.
- Reduction of peripheral resistance (reduction of afterload).
Indications
- Seizure treatment of angina pectoris.
- Severe left heart failure with or without pulmonary edema.
Dosage
According to the professional information. Usually one capsule is sufficient to stop an attack of angina. The capsule is bitten and the contents mixed with saliva are kept in the mouth. The empty capsule is spat out again after the onset of the effect. The active ingredient rapidly enters the bloodstream through the mucous membrane and the effects occur within two to four minutes. The capsules should not be swallowed due to high first-pass metabolism and low oral bioavailability. Because of the effects on the circulation, ingestion is best done while seated.
Contraindications
- Hypersensitivity
- Certain cardiovascular diseases, e.g. hypotension, circulatory failure.
- Combination with phosphodiesterase-5 inhibitors such as sildenafil (Viagra, generics).
Full precautions can be found in the drug label.
Interactions
Drug-drug interactions have been described with the following substances:
- Antihypertensive agents, alcohol
- Phosphodiesterase-5 inhibitors can cause a dangerous drop in blood pressure and are therefore contraindicated.
- Other nitrates, NO donors, amyl nitrite.
- Dihydroergotamine
- Heparin
Adverse effects
The most common possible adverse effects include headache (nitrate headache), low blood pressure with a rapid pulse, drowsiness, dizziness, and weakness.