Nitroglycerin

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[edit] BRAND NAMES

[edit] STRUCTURE

Nitroglycerin.jpg

[edit] MECHANISM OF ACTION

Angina is usually caused by insufficient blood supply and oxygen to the heart. Nitrates work by relaxing the blood vessels to the heart, so that the blood and oxygen supply to the heart is increased.

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. These events lead to dephosphorylation of myosin light chains, which regulate the contractile state in smooth muscle, and result in vasodilatation.

[edit] INDICATIONS

Nitrates are used to prevent and treat the symptoms of angina (chest pain).

Nitrates come in several forms, including regular, extended-release or sublingual tablets, transdermal patch and oral spray.

Depending on the type of dosage form and how it is taken, nitrates are used to treat angina in 3 ways:

  • To relieve an attack that is occurring by using the medicine when the attack begins;
  • To prevent attacks (prophylaxis) from occurring by using the medicine just before an attack is expected to occur; r
  • To reduce the number of attacks that occur by using the medicine regularly on a long-term basis.

[edit] DOSAGE

Sublingual tablets:

  • Treatment of acute attacks: When angina starts, 0,5 mg or 0,6 mg should be taken every 3 minutes untill cessation of pain or limiting side effects, such as headache or light headedness supervene. The patient should preferably rest in the sitting position because of the risk of symptomatic postural hypotension. The onset of the vasodilatory effect occurs approximately 1 to 3 minutes after sublingual nitroglycerin administration and reaches a maximum by 5 minutes postdose. Effects persist for at least 25 minutes.
  • Prophylaxis: 0,5 mg or 0,6 mg may be used prior to activity which is likely to precipitate angina pectoris.


Transdermal patch: Transdermal patch is not intended for the immediate relief of acute attacks of angina pectoris; if these occur, rapid-acting nitrate preparations should be used. the lowest effective dose should be prescribed. The application site should be changed regularly to prevent local irritation. Development of tolerance or attenuation of therapeutic effect commonly occurs with prolonged or frequent administration of long-acting nitrates, including transdermal systems.
Treatment should be initiated with one Transdermal patch TTS 5 (25 mg/ 10 cm2) daily. According to the clinical response the daily dose can then be titrated upwards to:

  • One Transdermal patch TTS 10 (50 mg/ 20 cm2) (normal maintenance dose)
  • One Transdermal patch TTS 10 plus one Transdermal patch TTS 5
  • Two Transdermal patch TTS 10

[edit] CONTRAINDICATIONS

  • Allergic reactions to organic nitrates are extremely rare, but they do occur. Nitroglycerin is contraindicated in patients who are allergic to it.
  • Sublingual nitroglycerin therapy is contraindicated in patients with early myocardial infarction, severe anemia and increased intracranial pressure.
  • Administration of Nitroglycerin is contraindicated in patients who are using a phosphodiesterase-5 (PDE-5) inhibitor (e.g., sildenafil, tadalafil, vardenafil and avanafil) since these compounds have been shown to potentiate the hypotensive effects of organic nitrates.
  • Acute circulatory failure associated with marked hypotension (shock).

[edit] PRECAUTIONS

[edit] INTERACTIONS

  • Nitroglycerin is contraindicated for use with sildenafil, tadalafil, vardenafil and avanafil. When these drugs are taken with nitrates, blood pressure can lower drastically resulting in dizziness, lightheadedness or fainting.
  • Concomitant treatment with calcium antagonists, ACE inhibitors, beta-blockers, diuretics, antihypertensives, tricyclic antidepressants and major tranquillisers may potentiate the blood pressure-lowering effect of nitroglycerin, as may alcohol.
  • Concurrent administration of Nitroglycerin with dihydroergotamine may increase the bioavailability of dihydroergotamine. This warrants special attention in patients with coronary artery disease, because dihydroergotamine antagonises the effect of nitroglycerin and may lead to coronary vasoconstriction.

[edit] PREGNANCY AND LACTATION

[edit] SIDE EFFECTS

Nitroglycerin commonly causes dose-dependent headaches due to cerebral vasodilatation. These often regress after a few days despite the maintenance of therapy. If headaches persist during intermittent therapy, they should be treated with mild analgesics. Other possible adverse reactions include flushing or redness of the skin, dizziness, weakness or fainting, rapid heart beat, nausea or vomiting.

[edit] RELATED LINKS

[edit] BIBLIOGRAPHY

[edit] REFERENCES

Antianginals
Beta blockers Cardioselectives Acebutolol   Atenolol   Metoprolol
Non-Cardioselectives Oxprenolol  Nadolol   Propranolol   Sotalol
Calcium channel blockers Class I agents (potent negative inotropic effect) Verapamil
Class II agents (do not depress conduction or contractility) Amlodipine   Nifedipine
Class III agent (negligible inotropic effect and causes almost no reflex tachycardia) Diltiazem
Nitrates Isosorbide dinitrate   Isosorbide mononitrate  Nitroglycerin   Pentaerythritol tetranitrate
Others Ranolazine