Objective: To evaluate the efficacy and safety of tacrolimus in patients with generalized myasthenia gravis (MG).
Methods: A total of 69 cases admitted to our hospital were given 2-6 mg/day tacrolimus (FK506) for 12 months. The MG absolute and relative clinical scores were used to monitor the efficacy of tacrolimus. Clinical evaluation was conducted at month 1, 3, 6, and 12, while the serum concentration of FK506 was measured at one month after administration of tacrolimus for one month.
Results: The therapeutic response presenting as improved muscular strength showed within one month after administration of tacrolimus. The overall response rates (MG relative clinical score ≥ 25%) at month 1, 3, 6 were 81.2%, 87.6%, 92.2% respectively. It reached 93.8% by the final visit at month 12. MG score to evaluate disease severity decreased significantly as the subjects continued to take tacrolimus. Statistic analysis suggested that the serum concentration of FK506 was correlated with its therapeutic effect. Serum trough levels in remission and response groups [(7.1 ± 3.9) µg/L and (6.3 ± 3.8) µg/L, respectively] were significantly higher than that of no response group [(3.4 ± 1.3) µg/L]. The most common adverse effects included hyperglycemia (5 cases), myelosuppression (3 cases), and dizziness tinnitus (3 cases), majority of which were temporary and manageable.
Conclusions: Our study has shown that tacrolimus significantly improved muscular strength of generalized MG patients. The treatment is well tolerated. The therapeutic effect of tacrolimus is observed within 1 month after initial use. Adverse events were manageable and not common.