Diphtheria Antitoxin. - Not official. - When the bacillus of diphtheria grows in the body it produces toxins, albumoses, and an organic acid, and provokes the formation of a substance (called an antitoxin) which is found in the blood. This antitoxin is an antidote to the toxin of the diphtheria bacillus, and it is largely owing to the production of it that the patient is enabled to survive, and his chances of surviving are enhanced if antitoxin is administered to him to aid that which is formed in his body.

Source

Diphtheria bacilli are grown in a flask containing some nutrient broth {e.g., meat broth), to which 0.5 per cent. of sodium chloride and 2 per cent. of commercial peptone have been added. At the end of some weeks the bacilli are filtered off, and the fluid left contains a large amount of diphtheria toxin, and it should be of such strength that .01 c.c. 1 1/2 m. of it will kill a good-sized guinea pig. From .02 to 1.00 c.c. 3 to 15 m. of it is aseptically injected into the jugular vein of ahorse; this produces slight symptoms. As soon as they are past a larger dose is injected, and so the dose is gradually increased until 100 c.c. 25 fl. dr. or more are given at each injection. This leads to the formation of a large amount of antitoxin in the blood serum. At the end of some months the horse is bled to 8 liters quarts in a sterilized vessel, the blood coagulates, and the antitoxic serum is put into sterilized bottles and hermetically sealed, a little carbolic acid or other antiseptic being added to prevent decomposition.

The details may be modified, as horses vary in their reaction to the toxin, and toxins vary in strength, but the essentials of the method always remain the same.

Mode of Administration. - The antitoxic serum has been shown to be useless when given by the mouth, perhaps because it is destroyed in the liver. Therefore it is always injected subcutaneously; usually between the shoulders or on the side of the abdomen. Before injection the skin must be thoroughly washed with an antiseptic, and all ordinary antiseptic precautions should be taken. After injection the puncture should be healed with antiseptic gauze, iodoform and collodion. The antitoxin should be taken from a fresh bottle. A special syringe, so constructed that all the parts of it can be boiled before use is employed.

Dose. - It is better to give a small dose of a concentrated rather than a large dose of a dilute antitoxin. The dose is the same for children and adults. The strength of it, which is stated on the bottle, varies between 200 and 2500 units per cubic centimeter, but it is usually about 500. The antitoxin must be obtained from a reliable source. The quantity given should be such that from 4000 to 12,000 units or even more are injected in the first twenty-four hours after the patient comes under treatment. This amount may be divided into two or three doses, but should be repeated on the second and third days, if accessary. A unit is the smallest quantity of antitoxic serum, which when mixed with a certain quantity of a standard diphtheritic toxin and with it injected into the subcutaneous tissue of a healthy guinea-pig weighing from 250 to 300 grammes 8 to 10 oz. , protects the animal from death within four days.

It is impossible in a work like this to give a more precise definition, for all diphtheritic toxin consists of a toxin proper, which is poisonous, and toxoid bodies which, although not poisonous, will neutralize the antitoxic properties of antitoxic serum. Therefore, to standardize antitoxic serum it must be tested against diphtheritic toxin in which the proportion of toxins proper and toxoids and the neutralizing activity of the latter as regards antitoxin are known and constant. Such a standard toxin is kept in the Government testing department in Berlin, and the strength of all diphtheritic antitoxins should be expressed in terms of it.