This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
These are remedies which prevent or relieve spasm.
Spasm is contraction of voluntary or involuntary muscles, in a way that is unnecessary or injurious to the organism generally. The spasmodic contraction of muscles may sometimes be excessive in degree, as in the calves of the legs in cramp, or in the fibres of the intestinal walls in colic. Sometimes it is not excessive in degree, but are merely out of place, as, for example, in the slight twitchings of the face or fingers which occur in mild cases of chorea.
Spasm may affect single muscles, or it may affect groups of muscles and the nerve-centres by which they are set in action; these centres may sometimes be very limited in extent, but sometimes a great number, or indeed most of the motor centres in the body, may be involved, as in the convulsions of hysteria. Spasm is, indeed, a kind of insubordination in which the individual muscles or nerve-centres act for themselves without reference to those higher centres which ought to co-ordinate their action for the general good of the organism. It may be due, therefore, either to excess of action in the muscles or local centres, or diminished power of the higher co-ordinating centres. As a rule it is due to diminished action of the co-ordinating or inhibitory centres, rather than to excess of action in the motor centres; it is, therefore, a disease rather of debility and deficient co-ordination than of excessive strength.
Cramps in the muscles may come on from their exhaustion by excessive exertion, the waste products of their functional activity appearing to act as local irritants. This is relieved by the removal of these waste products; as, for example, by shampooing. In the intestine, cramp may be due to the presence of a local irritant, which ought in the normal condition to produce increased peristalsis, and thus ensure the speedy removal of the offending substance. From some abnormal condition the muscular fibres around the irritant contract excessively, and do not pass on the stimulus to those adjoining. From this want of co-ordination painful and useless spasm occurs. In order to remove it we apply warmth to the abdomen so as to increase the functional activity, both of the muscular fibres and of the ganglia of the intestine (pp. 138, 140). Peristalsis then occurring instead of cramp, the pain disappears, and the offending body is passed onwards and removed. Or we give internally aromatic oils, which will have a tendency to increase the regular peristalsis; or yet again, we may give opium for the purpose of lessening the sensibility of the irritated part, or the nerves connected with it, and thus again bringing it into relationship with other parts of the body. General antispasmodics may act either
(1) By increasing the power of the higher nervous centres to keep the lower ones and the muscles in proper subordination, or (2) By lessening the activity of over-excited muscles or lower nervous centres.
On this account we find stimulants and antispasmodics very much classed together. Those drugs which stimulate the circulation and increase the nutrition of the higher nerve-centres and the co-ordinating power, tend to prevent spasm. Thus, small quantities of alcohol and ether, by acting in this way, tend to prevent general spasm, as in hysteria, nervous agitation, or trembling, or remove local spasm, as in colic.
Camphor, which is frequently used as an antispasmodic, has a stimulant action on the brain, spinal cord, circulation, and respiration. It is probable that such antispasmodic powers as it possesses are due to its exciting the higher centres, and increasing their inhibitory powers over the lower (p. 214). Bromo-camphor has a somewhat similar action.
Valerian, asafoetida, musk, castor, and other aromatic substances, have an antispasmodic action which we do not understand. It is possible that they affect some part of the brain particularly, so as to increase its regulating power, in much the same way as camphor.
Other antispasmodics, such as bromide of potassium, lessen the irritability of motor centres. Borneol and menthol have a depressing and finally paralysing effect upon motor, sensory, and reflex centres in the brain and spinal cord. In this respect they differ greatly from ordinary camphor, which has an exciting action upon these structures, though they may perhaps be still more useful as antispasmodics.
Other antispasmodics, instead of lessening the irritability of nerve-centres, may paralyse the structures through which the nerves act. Thus, nitrite of amyl appears to arrest the spasm of the vessels in angina pectoris, by causing paralysis of the vessels themselves or of the peripheral ends of the vaso-motor nerves.
It has already been mentioned, that a healthy condition of the various parts of the body depends on proper nutrition and proper removal of waste. Therefore, when there is a tendency to spasm, the diet should be plain, but nutritious. Those conditions which tend to cause excessive waste should be avoided, such as exciting emotions, excessive bodily or mental work, a close atmosphere, and late hours. Attention must be paid also to the proper removal of all waste, by the use of purgatives, cholagogues, or diuretics if necessary.
Great irritability of the nervous system is usually observed in gouty subjects before an attack of gout comes on. It is uncertain to what this irritability is due, but it may not improbably be caused by the retention within the body of the products of tissue-waste. Some years ago there was considerable discussion regarding the active ingredient of bromide of potassium, some attributing its antispasmodic action to the bromine, and others to the potassium. It occurred to me that possibly its action might be partly due simply to its action as a saline leading the patient to drink more water, and thus assisting the elimination of the products of tissue-waste. I accordingly tried 30-grain doses of chloride of sodium in cases of epilepsy. In some it did little or no good, but in a few it appeared to have nearly as powerful an action as bromide of potassium.
Antispasmodics are used in convulsive diseases.
The antispasmodics used in hysteria may be divided into substances which exert on the higher nerve-centres a sedative, tonic, or stimulant action, thus :
which have a power-ful odour, and probably act on the higher centres through the olfac-tory organs, either by direct application or during their elimination (p. 41).
Derived from the genital organs of animals.
Similar in the nature of their odour to the above, though derived from plants.
Containing sulphur oils.
In chorea, arsenic, conium, the salts of copper and zinc.
In spasmodic asthma, lobelia, stramonium.
In spasm of the blood-vessels, nitrite of amyl and other nitrites.