Teriparatide administration

Tumorigenidty Osteosarcoma is postulated as a potential adverse reaction to parathyroid hormone analogues, based on animal studies, and another case has been reported in a 67-year-old man who took teriparatide 20 micrograms/day subcutaneously for 2 months, 7 years after a course of radiotherapy for recurrent prostate cancer [65 ]. However, the osteosarcoma occurred within the field of previous radiotherapy and the time course suggested that the osteosarcoma may have been present before teriparatide administration. The authors noted that 430 000 patients have been treated with teriparatide for osteoporosis and that there have been only two reported cases of osteosarcoma, which is consistent with the expected population incidence of 4-5 per million. However, the effect of teriparatide on the growth of an undiagnosed osteosarcoma is unknown, and so teriparatide should be used with caution in patients who have had previous radiotherapy. 

Cosman F, Lane NE, Bolognese MA, Zanchetta JR, Garcia-Hemandez PA, Sees K, Matriano JA, Gaumer K, Daddona PE. Effect of transdermal teriparatide administration on bone mineral density in postmenopausal women. J Clin Endocrinol Metab 2010 95(1) 151-8. 

Teriparatide (Forteo) [Antiosteoporotic/Parathyroid Hormono] WARNING T Osteosarcoma risk in animals, therefore only use in pts for whom the potential benefits outweigh risks Uses Severe/refractory osteoporosis Action PTH (recombinant) Dose 20 meg SQ daily in thigh or abd Caution [C, /-] Contra w/ Paget Dz, prior radiation, bone metastases, T Ca caution in urolithiasis Disp Inj SE Orthostatic X BP on administration, N/D, T... 

Fig. 12.3 Effects of daily teriparatide (TPTD) administration on biomarkers of bone formation (bone ALP and PICP) and bone resorption (DPD/Cr and NTx/Cr) in postmenopausal women with osteoporosis. Changes in bone formation markers at 1 month were significantly correlated with improvements in bone structure after 22 months of treatment (from [48]). 

First, Mrs TY should be advised that teriparatide is only available as an injection and, therefore, Mrs TY may not find this an acceptable route of administration. Second, the NICE guidelines state that teriparatide should only be used in postmenopausal women who are unable to take bisphosphonates or strontium or who have had an unsatisfactory response bisphosphonates. They must also have experienced more than two fractures and have a T-score which fits into the range specified in the NICE guidance (NICE 2008). 

The polypeptide parathormone is released from the parathyroid glands when the plasma Ca2+ level falls. It stimulates osteoclasts to increase bone resorption in the kidneys it promotes calcium reabsorption, while phosphate excretion is enhanced. As blood phosphate concentration diminishes, the tendency of Ca2+ to precipitate as bone mineral decreases. By stimulating the formation of vitamin D hormone, parathormone has an indirect effect on the enteral uptake of Ca2+ and phosphate. In parathormone deficiency, vitamin D can be used as a substitute that, unlike parathormone, is effective orally. Teriparatide is a recombinant shortened parathormone derivative containing the portion required for binding to the receptor. It can be used in the therapy of postmenopausal osteoporosis and promotes bone formation. While this effect seems paradoxical in comparison with hyperparathyroidism, it obviously arises from the special mode of administration the once daily s.c. injection generates a quasi-pulsatile stimulation. Additionally, adequate intake of calcium and vitamin D must be ensured. 

I Administration. Teriparatide is contraindicated in patients with Paget s disease of the bone, unexplained elevations in alkaline phosphatase, or a history of previous skeletal radiation therapy (a blackbox warning from the manufacturer). Osteosarcoma was seen in a small number of rats, but the incidence in humans is unknown but of potential concern. 

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