[Assessment of different regimens of diphtheria serotherapy]

Efficacy of different treatment regimens with equine diphtheria antitoxin (EDA) was assessed on clinical samples as well as in experiments on animals.

Protective properties and serum concentration kinetics of heterologous antibodies was studied on 12 rabbits and 51 guinea pigs after intramuscular injection of different doses of EDA, in serum samples from 26 patients, which received one intramuscular injection of EDA in various doses as well as in serum samples from 10 patients with diphtheria of different severity, which were treated with EDA in total course dose 100,000-1,500,000 IU. Antitoxin concentration in serum sample was measured with passive hemagglutination assay as well as Jensen toxin neutralization test on rabbits.

Experiments on laboratory animals received EDA in dose 150 IU/kg showed high protective effect. For example, rabbits with antitoxin level 1.0-1.25 IU/ ml in serum 24 hours after injection of EDA were 50-250 times resistant to dermonecrotic effect of diphtheria toxin compared with rabbits not received EDA. Guinea pig with antitoxin level 0.5-2.0 IU/ ml in serum 2-48 hours after injection of EDA in dose 150 IU/kg were all protected against 35-50 LD50 of diphtheria toxin. After termination of EDA injection there was sharp decrease of antitoxin level and it was not detected in serum 7 days after. Increase of antitoxin level in serum of animals was not adequate to quantity of injected EDA. Study of serum samples from 26 patients received one intramuscular injection of different doses of EDA showed that doses of antitoxin from 20,000 to 30,000 IU resulted in its presence in serum in concentration 0.5-3.0 IU/ml whereas injection of 50,000 IU or 70,000-100,000 IU resulted in serum concentrations 1.25-10.0 IU/ ml and 2.5-20.0 IU/ml respectively.

Relatively low doses of EDA provided relatively high level of protection against diphtheria toxin that should be taken into account during treatment of diphtheria patients.