DESCRIPTION
Tetanus Immune Globulin (Human) -- BayTet® treated with solvent/detergent is a sterile solution of tetanus hyperimmune immune globulin for intramuscular administration; it contains no preservative. BayTet is prepared by cold ethanol fractionation from the plasma of donors immunized with tetanus toxoid. The immune globulin is isolated from solubilized Cohn Fraction II. The Fraction II solution is adjusted to a final concentration of 0.3% tri-n-butyl phosphate (TNBP) and 0.2% sodium cholate. After the addition of solvent (TNBP) and detergent (sodium cholate), the solution is heated to 30°C and maintained at that temperature for not less than 6 hours. After the viral inactivation step, the reactants are removed by precipitation, filtration and finally ultrafiltration and diafiltration. BayTet is formulated as a 15-18% protein solution at a pH of 6.4-7.2 in 0.21-0.32 M glycine. BayTet is then incubated in the final container for 21-28 days at 20-27°C. The product is standardized against the U.S. Standard Antitoxin and the U.S. Control Tetanus Toxin and contains not less than 250 tetanus antitoxin units per container.
The removal and inactivation of spiked model enveloped and non-enveloped viruses during the manufacturing process for BayTet has been validated in laboratory studies. Human Immunodeficiency Virus, Type 1 (HIV-1), was chosen as the relevant virus for blood products; Bovine Viral Diarrhea Virus (BVDV) was chosen to model Hepatitis C virus; Pseudorabies virus (PRV) was chosen to model Hepatitis B virus and the Herpes viruses; and Reo virus type 3 (Reo) was chosen to model non-enveloped viruses and for its resistance to physical and chemical inactivation. Significant removal of model enveloped and non-enveloped viruses is achieved at two steps in the Cohn fractionation process leading to the collection of Cohn Fraction II: the precipitation and removal of Fraction III in the processing of Fraction II + IIIW suspension to Effluent III and the filtration step in the processing of Effluent III to Filtrate III. Significant inactivation of enveloped viruses is achieved at the time of treatment of solubilized Cohn
Fraction II with TNBP/sodium cholate.
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CLINICAL PHARMACOLOGY
The occurrence of tetanus in the United States has decreased dramatically from 560 reported cases in 1947, when national reporting began, to a record low of 48 reported cases in 1987 1 . The decline has resulted from widespread use of tetanus toxoid and improved wound management, including use of tetanus prophylaxis in emergency rooms. 2
BayTet supplies passive immunity to those individuals who have low or no immunity to the toxin produced by the tetanus organism, Clostridium tetani. The antibodies act to neutralize the free form of the powerful exotoxin produced by this bacterium. Historically, such passive protection was provided by antitoxin derived from equine or bovine serum; however, the foreign protein in these heterologous products often produced severe allergic manifestations, even in individuals who demonstrated negative skin and/or conjunctival tests prior to administration. Estimates of the frequency of these foreign protein reactions following antitoxin of equine origin varied from 5%-30%. 3-6 If passive immunization is needed, human tetanus immune globulin (TIG) is the product of choice. It provides protection longer than antitoxin of animal origin and causes few adverse reactions. 2
Several studies suggest the value of human tetanus antitoxin in the treatment of active tetanus. 7,8 In 1961 and 1962, Nation et al, 7 using Hyper-Tet treated 20 patients with tetanus using single doses of 3,000 to 6,000 antitoxin units in combination with other accepted clinical and nursing procedures. Six patients, all over 45 years of age, died of causes other than tetanus. The authors felt that the mortality rate (30%) compared favorably with their previous experience using equine antitoxin in larger doses and that the results were much better than the 60% national death rate for tetanus reported from 1951 to 1954. 9 Blake et al, 10 however, found in a data analysis of 545 cases of tetanus reported to the Centers for Disease Control from 1965 to 1971 that survival was no better with 8,000 units of TIG than with 500 units; however, an optimal dose could not be determined.
Serologic tests indicate that naturally acquired immunity to tetanus toxin does not occur in the United States. Thus, universal primary vaccination, with subsequent maintenance of adequate antitoxin levels by means of appropriately timed boosters, is necessary to protect persons among all age groups. Tetanus toxoid is a highly effective antigen; a completed primary series generally induces protective levels of serum antitoxin that persist for >/= 10 years. 2
Passive immunization with BayTet may be undertaken concomitantly with active immunization using tetanus toxoid in those persons who must receive an immediate injection of tetanus antitoxin and in whom it is desirable to begin the process of active immunization. Based on the work of Rubbo, 11 McComb and Dwyer, 12 and Levine et al, 13 the physician may thus supply immediate passive protection against tetanus, and at the same time begin formation of active immunization in the injured individual which upon completion of a full toxoid series will preclude future need for antitoxin.
Peak blood levels of IgG are obtained approximately 2 days after intramuscular injection. The half-life of IgG in the circulation of individuals with normal IgG levels is approximately 23 days. 14
In a clinical study in eight healthy human adults receiving another hyperimmune immune globulin product treated with solvent/detergent, Rabies Immune Globulin (Human), BayRab®, prepared by the same manufacturing process, detectable passive antibody titers were observed in the serum of all subjects by 24 hours post injection and persisted through the 21 day study period. These results suggest that passive immunization with immune globulin products is not affected by the solvent/detergent treatment.
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