This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
An alkaloid obtained from nux vomica, and also obtainable from other plants of the Loganiaceae.
Properties : Strychnin occurs as colorless, transparent crystals or a white crystalline powder, odorless and having an intensely bitter taste. It is very slightly soluble in water (1:6400) and soluble in alcohol (1:110).
Incompatibilities: The salts of strychnin are incompatible with alkalies, alkali carbonates, iodids, bromids, arsenates and arsenites.
Action and Uses: Strychnin stimulates the reflex activity of the spinal cord, but produces little or no effect on the higher nervous centers. Both the sensory and motor centers are affected. Small doses increase the acuity of both sight and hearing. Large doses raise the blood-pressure by causing a constriction of the arterioles. It seems to have little direct effect on the heart. It stimulates the respiratory center, increasing the rapidity of the respirations. In poisonous doses it produces tonic convulsions similar to those of tetanus, but the trismus is less marked. Between the attacks there is usually complete relaxation of the affected muscles. The convulsions are spinal, but not cerebral in origin. Death may occur during a convulsion from fixation of the chest by spasm of the respiratory muscles or during the interval from medullary paralysis.
Strychnin is used as a bitter tonic, generally in the form of a preparation of nux vomica. It is also serviceable as a tonic to the muscular system. It is chiefly employed as a respiratory stimulant in cases of depression of the respiratory center by narcotic or other poisoning. It is used for this purpose in several diseases of the respiratory organs, such as bronchitis, especially senile, pneumonia, etc.
Strychnin is much employed as a heart tonic, but in many cases improperly. It acts as a heart tonic chiefly by raising the blood-pressure. It should be used for its cardiac effect, if at all, in conditions of low blood-pressure. Thus it may be employed in pneumonia, diphtheria and other infections in which death results from the lowered blood-pressure. Even in these conditions its utility has been overestimated. It has been recommended in conditions of shock and collapse, but in the experience of some it is not effective in these conditions (Crile).
Strychnin is serviceable in some forms of paralysis. It is of no value when the paralysis results from an organic lesion and should not be used in conditions of inflammation of the nerve centers. It may be employed in paralysis due to poisons, such as lead, and in postdiphtheric paralysis. It is also of value in paralysis due to the cortical lesions, if used in moderate doses, to maintain the nutrition of the paralyzed muscles. In incontinence of urine, due to paresis of the vesical sphincter, it is useful, but if the incontinence depends on spasm atropin is more serviceable. Strychnin is useful in amblyopia, acting best in disturbance of vision unattended by changes visible with the ophthalmoscope, especially hysteric and neurasthenic forms. In lesions of the optic nerve it frequently produces an improvement in vision which, however, is only temporary. It is used in acute and chronic alcoholism. It is added to cathartics in the treatment of chronic constipation.
Dosage: From 0.0005 to 0.005 gm. or from 1/100 to 1/10 grain, three times a day or even as often as once in three hours.
In threatening respiratory or cardiac paralysis, strychnin must sometimes be used in quite large doses. In these cases it has been advised to push the remedy until twitching of the fingertips occurs. Too large doses, however, should not be given, as it is possible to bring about a strychnin paralysis of the respiratory center. In such cases the strychnin should always be given hypodermically. In cardiac failure, strychnin, if given too frequently or in too large doses, may do more harm than good by causing irritability of the heart. In toxic amblyopia it is sometimes desirable to use large doses. It has been recommended to give as much as 1/13 grain per day (Nagel)