amyl nitrite

Available forms
Available by prescription only
Nasal inhalant: 0.3 ml

Indications and dosages
 Angina pectoris. Adults: 0.18 to 0.3 ml by inhalation (one glass ampule inhaler), p.r.n.
 Adjunct treatment of cyanide poisoning. Adults and children: 0.3 ml by inhalation for 15 to 30 seconds; repeat q 60 seconds until I.V. sodium nitrite infusion and I.V. sodium thiosulfate infusion are available.

Pharmacodynamics
Vasodilating action: Drug reduces myocardial oxygen demand by decreasing left ventricular end-diastolic pressure (preload) and systemic vascular resistance and arterial pressure (afterload). It also increases collateral coronary blood flow. By relaxing vascular smooth muscle, it produces generalized vasodilation. Amyl nitrite also relaxes all other smooth muscle, including bronchial and biliary smooth muscle. In cyanide poisoning, it converts hemoglobin to methemoglobin, which reacts with cyanide to form cyanmethemoglobin.

Pharmacokinetics
Absorption: Inhaled drug is absorbed readily through the respiratory tract.
Distribution: No information available.
Metabolism: Amyl nitrite, an organic nitrite, is metabolized by the liver to form inorganic nitrites, which are much less potent vasodilators than the parent drug.
Excretion: One-third of the inhaled dose is excreted in urine.

Contraindications and precautions
Contraindicated in pregnant patients, patients hypersensitive to nitrites, and patients with severe anemia, angle-closure glaucoma, orthostatic hypotension, or increased intracranial pressure.
  Use cautiously in patients with glaucoma, volume depletion, and hypotension.

Interactions
Drug-drug. Antihypertensives, beta blockers, phenothiazines, sildenafil: May cause excessive hypotension. Monitor blood pressure.
Drug-lifestyle. Alcohol use: May cause excessive hypotension. Discourage alcohol use.

Adverse reactions
CNS: headache, sometimes with throbbing; dizziness; weakness.
CV: orthostatic hypotension, tachycardia, flushing, palpitations, fainting.
GI: nausea, vomiting.
Hematologic: methemoglobinemia.
Skin: cutaneous vasodilation, rash.
Other: hypersensitivity reactions.

Effects on lab test results
None reported.

Overdose and treatment
Overdose may cause methemoglobinemia, characterized by blue skin and mucous membranes, hypotension, tachycardia, palpitations, skin changes, diaphoresis, dizziness, syncope, vertigo, headache, nausea, vomiting, anorexia, increased intracranial pressure, confusion, moderate fever, and paralysis. Hypoxia may lead to metabolic acidosis, cyanosis, seizures, coma, and cardiac collapse.
 Treat with high flow oxygen and methylene blue. Usual dose of methylene blue for adults and children is 1 to 2 mg/kg I.V. given slowly over several minutes. In severe cases, this dose may be repeated only once; doses exceeding 4 mg/kg may produce methemoglobinemia.

Special considerations
• Amyl nitrite therapy alters the Zlatkis-Zak color reaction, causing a false decrease in serum cholesterol levels.
• Drug is rarely used as an antianginal.
• Keep patient sitting or lying down during and immediately after inhalation. Crush ampule (has a woven gauze covering) between fingers and hold to nose for inhalation.
• Monitor patient for orthostatic hypotension; don’t allow patient to make rapid postural changes while inhaling drug.
• Drug is highly flammable; keep away from open flame and extinguish all cigarettes before use.
• Drug is used illegally to enhance sexual pleasure. Street names include Amy and poppers.
Breast-feeding patients
• It isn’t known if amyl nitrite appears in breast milk; risk and benefit must be considered.
Pediatric patients
• Safety and efficacy haven’t been established.
Geriatric patients
• Orthostatic hypotensive effects may be more likely to occur in elderly patients.

Patient education
• Explain that ampule must be crushed to release drug.
• Warn patient to use drug only when seated or lying down.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use