The relationship of plasma levels of pyridostigmine to clinical effect in patients with myasthenia gravis.

The relationship between plasma levels of pyridostigmine to clinical evaluation of muscle power was examined in nine patients with myasthenia gravis during treatment with pyridostigmine in doses of 60 to 1040 mg daily. Five of the nine subjects demonstrated a trend towards a positive correlation, but in only two of them was this statistically significant at p < 0.05. In addition, the presence or absence of a possible correlation between muscle power and plasma concentration was not related to the duration of the disease, additional prednisolone therapy or thymectomy.