Nitrite of amyl (C3H11-O-NO). Dilutions with alcohol.
THE pharmacopoeial amyl nitrite is a mixture of the nitrites of amyl, butyl, propyl and ethyl. They resemble each other closely; the more unstable the compound the more rapid and evanescent is the effect produced by it, and amyl nitrite is the most unstable of them all.
Circulation.-When amyl nitrite is inhaled there immediately takes place hot flushing of the head and neck, throbbing of the arteries all over the body, tumultuous action of the heart with a sensation of constriction in the cardiac region and an accelerated. full, dicrotic pulse of low tension; the head feels intensely full and the temporal arteries visibly pulsate, the eyes protrude, ophthalmoscopic examination shows the veins of the disc to be enlarged, varicose and tortuous, and there is a bursting-outwards sensation in the ears. There is a full feeling in the throat along the pulsating carotids, and the collar must be loosened; dyspnoea and asthmatic breathing occur the patient feels he must have fresh air.
These symptoms are due to the action of amyl nitrite on unstriped muscle, which it depresses and thus causes dilation of both arteries and veins, especially those of the head and neck and of the abdominal organs. The systemic system of vessels is more affected than the pulmonary. The nervous system is not affected except secondarily to the circulatory, and the terminations of the nerves remain intact; it is upon the unstriped muscle of the blood-vessels that amyl nitrite exerts blood-vessels is a fall in blood-pressure; this produces anaemia of the brain, which in turn (1) depresses the tone of the inhibitory cardiac centre and so leads to quickening of the heart beats, and (2) rouses the respiratory centre and causes acceleration of the respiration. The cutaneous vessels of the head and neck only are affected, and therefore these are the only parts where visible blushing occurs. The bronchial muscle tissue is relaxed. Larger doses depress the cardiac muscle and consequently slow and weaken its action. The convulsions that occur after large doses are of cerebral origin and are probably due to anaemia of the brain.
The fall of blood-pressure caused by amyl nitrite mostly passes off in about five minutes and entirely in twenty minutes or less.
The nitrites change haemoglobin to met-haemoglobin and nitric-oxide haemoglobin, which gives the blood a dark chocolate colour; but in man too little is thus transformed to produce any physiological effect. In the blood amyl nitrite breaks up with the formation of nitrites of the alkalis which undergo partial oxidation and appear in the urine as nitrites and nitrates. Amyl nitrite affects the sight curiously: when a dark object is looked at on a white background it seems surrounded by a yellow ring and that again by a blue one.
Amyl nitrite is used antipathically and homoeopathically.
ANTIPATHICALLY it is principally employed to relieve the paroxysms of pain in angina pectoris; a capsule is broken in a handkerchief and the vapour inhaled; it seems to act by relieving the tension of the circulation. It also temporarily relieves cardiac dyspnoea when the heart is failing from the excessive work thrown upon it by a high blood-pressure.
It is used for migraine and other neuralgias associated with pallor of the the surface due to the constriction of the arterioles. It is sometimes useful in asthma by relaxing bronchial spasm. It has been used to forestall an epileptic attack when there is a sufficient interval between the aura and the paroxysms to enable it to be administered. Other uses have been to warm the patient in the shivering stage of the ague fever and to relieve pain in spasmodic gastrodynia and dysmenorrhoea. In all these cases the action is palliative and temporary, not curative. It is contra-indicated in accidents from chloroform poisoning, in anaesthesia, and whenever there is degeneration of cardiac muscle.
HOMOEOPATHICALLY its chief employment has been to cure flushings, whether occurring at the menopause or at other times. It has cured habitual blushing from slight cause. It calms a heart whose beats are at once tumultuous and feeble, and also some of the subjective symptoms of exophthalmic goitre. It is useful in congested headaches, especially those originating from an attack of sunstroke, but its value here is exceeded by glonoin.
1) Flushings of head and neck. Menopausic flushings.
2) Palpitations, with low tension pulse felt all over body.
3) Pulse quick, full and dicrotic.
4) Headaches from sunstroke.
5) Frequent deep yawning (kali carb.). Constant stretching.
6) Antipathically used for angina pectoris, cardiac dyspnoea, asthma.
From a warm room, mental and physical exertion.
From open-air exercise, cold air, cold water.