In patients with the adrenogenital syndrome, a single intramuscular injection of 40 mg every two weeks may be adequate. For maintenance of patients with rheumatoid arthritis , the weekly intramuscular dose will vary from 40 to 120 mg. The usual dosage for patients with dermatologic lesions benefited by systemic corticoid therapy is 40 to 120 mg of methylprednisolone acetate administered intramuscularly at weekly intervals for one to four weeks. In acute severe dermatitis due to poison ivy, relief may result within 8 to 12 hours following intramuscular administration of a single dose of 80 to 120 mg. In chronic contact dermatitis, repeated injections at 5 to 10 day intervals may be necessary. In seborrheic dermatitis, a weekly dose of 80 mg may be adequate to control the condition.
Mechanism of action: Topical immunotherapy acts by varied mechanisms of action. The most important mechanism is a decrease in CD4 to CD8 lymphocyte ratio which changes from 4:1 to 1:1 after contact immunotherapy. A decrease in the intra-bulbar CD6 lymphocytes and Langerhan cells is also noted. Happle et al, proposed the concept of ‘antigenic competition’, where an allergic reaction generates suppressor T cells that non-specifically inhibit the autoimmune reaction against a hair follicle constituent. Expression of class I and III MHC molecules, which are normally increased in areas affected by alopecia areata disappear after topical immunotherapy treatment 34 .A ‘cytokine inhibitor’ theory has also been postulated 34 .