Tetanus Immunoglobulin Dosing for Established Tetanus
Recommended Therapeutic Dose
For active tetanus disease, administer 3,000-6,000 units of human tetanus immunoglobulin (TIG) intramuscularly, which is 12-24 times higher than the 250-unit prophylactic dose used in wound management. 1
Administration Protocol
Give TIG as soon as possible after diagnosis to neutralize circulating tetanus toxin, though it cannot reverse toxin already bound to nerve endings 1
Administer TIG at a different anatomic site than tetanus toxoid-containing vaccine using separate syringes to prevent interference with the immune response 1
Always give concurrent tetanus toxoid vaccine (preferably Tdap if not previously received) at a separate site, as passive immunization does not confer long-term immunity and natural tetanus infection does not provide immunity 2
Alternative When Human TIG Is Unavailable
If human TIG is unavailable, equine antitetanus serum (ATS) can be used at 10,000-20,000 IU for treatment of established tetanus, though this is significantly less preferred due to higher rates of allergic reactions and shorter duration of protection 2
Human TIG is strongly preferred over equine ATS when available due to the substantially better safety profile 2
Intrathecal Administration Consideration
While the CDC guideline establishes the standard intramuscular dose of 3,000-6,000 units 1, older research suggests potential benefit from intrathecal administration:
Intrathecal TIG 250 IU showed superior outcomes compared to intramuscular TIG 1,000 IU in early tetanus, with only 6% worsening (3/49 patients) versus 31% worsening (15/48 patients) in the intramuscular group 3
Intrathecal administration was devoid of side effects and associated with lower mortality (2% vs 21%) 3
A more recent study using intrathecal TIG 1,000 IU plus intramuscular TIG 3,000 IU demonstrated 9% mortality and was cost-saving by preventing disease progression 4
However, intrathecal TIG requires preservative-free formulation to prevent meningeal irritation 4
Critical Clinical Pearls
Despite proper treatment with TIG, tetanus still carries significant mortality risk, emphasizing the critical importance of prevention through proper immunization 1
TIG only neutralizes circulating toxin and cannot reverse damage from toxin already bound to neural tissue, which explains why early administration is crucial 1, 2
Patients must complete a full 3-dose primary tetanus vaccination series after recovery, as neither natural infection nor passive immunization provides long-term immunity 2