indication

For the treatment of post-menopausal osteoporosis

pharmacology

Calcitonin inhibits bone removal by osteoclasts (bone remodeling cells) and promotes bone formation by osteoblasts. This leads to a net increase in bone mass. Calcitonin also reduces plasma calcium levels and enhances secretion of ions in the kidney.

mechanism of action

Calcitonin binds to the calcitonin receptor (found primarily in osteoclasts) which then enhances the production of vitamin D producing enzymes (25-hydroxyvitamine D-24-hydroxylase), leading to greater calcium retention and enhanced bone density. Binding of calcitonin to its receptor also activates adenylyl cyclase and the phosphatidyl-inositol-calcium pathway.

toxicity

Salmon calcitonin is devoid of embryotoxic, teratogenic and mutagenic potential.

biotransformation

Salmon calcitonin is primarily and almost exclusively degraded in the kidneys, forming pharmacologically inactive fragments of the molecule.

absorption

Salmon calcitonin is rapidly absorbed and eliminated. Bioavailability following subcutaneous and intramuscular injection in humans is high and similar for the two routes of administration (71% and 66%, respectively).

half life

50-80 minutes

route of elimination

Studies with injectable calcitonin show increases in the excretion of filtered phosphate, calcium, and sodium by decreasing their tubular reabsorption in the kidney.