Effect of antibodies to calcitonin on the pharmacokinetics and the pharmacodynamics of the hormone.

Calcitonin pharmacokinetics and pharmacodynamics were studied in two groups of patients with postmenopausal osteoporosis, who, treated for one year with intranasal Asu1.7-eel calcitonin (eCT), had (Ab+) and had not (Ab-) developed a specific immune response to the drug. The treatment consisted of daily intranasal administrations of eCT (80 IU/die) with 1 g supplemental calcium. Eight women who had developed specific antibodies and 5 who had not, were given 50 IU of CT i.m., in order to assess the pharmacokinetics and pharmacodynamics of the drug. The rise of serum levels of the hormone was significantly greater in Ab+ than in Ab- patients. At the end of the study, no significant differences in mineral bone loss between the two groups were found. In conclusion, the presence of antibodies to eCT does not represent a negative event in the therapy of osteoporosis, but significantly affects the pharmacokinetics of the drug.