Food and Drug Regulations

C.04.144 The human test dose of diphtheria toxin for Schick test, when fresh toxin containing no preservative is used, shall be determined by

• (a) intracutaneous injection into normal guinea pigs in mixtures with different proportions of diphtheria antitoxin, and one test dose mixed with 1/750 or more of a unit of antitoxin must cause no local reaction, but mixed with 1/1,500 or less of a unit of antitoxin must cause a definite local reaction of the type known as the “positive Schick reaction”; and

• (b) intracutaneous injection into normal guinea pigs without admixture with antitoxin, and 1/100 of one test dose must not cause, and 1/50 of one test dose must cause, a definite local reaction of the type known as the “positive Schick reaction”.