The increase of bone mineral density in the hip was also statistically significant compared to placebo, but only around 1.0% at study endpoint. Continued treatment up to 24 months lead to a continued increase in bone mineral density. Pharmacokinetics
Absorption
Subcutaneous administration of parathyroid hormone into the abdomen produces a rapid increase in plasma parathyroid hormone levels which reach peak at 1 to 2 hours after dosing. The mean half-life is approximately 1.5 hours. The absolute bioavailability of 100 micrograms of Preotact after subcutaneous administration in the abdomen is 55%. Distribution
The volume of distribution at steady-state following intravenous administration is approximately 5.4 liters. Intersubject variability is about 40%. Biotransformation
Parathyroid hormone is efficiently removed from the blood by a receptor-mediated process in the liver and is broken down into smaller peptide fragments. The fragments derived from the amino-terminus are further degraded within the cell while the fragments derived from the carboxy-terminus are released back into the blood and cleared by the kidney. These carboxy-terminal fragments are thought to play a role in the regulation of parathyroid hormone activity. Under normal physiological conditions full-length parathyroid hormone H constitutes only 5-30% of the circulating forms of the molecule, while 70-95% is present as carboxy-terminal fragments. Following administration of Preotact, carboxy-terminal fragments make up about 60-90% of the circulating forms of the molecule. Intersubject variability in systemic clearance is about 15%. Elimination
Parathyroid hormone is metabolised in the liver and to a lesser extent in the kidney. It is not excreted from the body in its intact form.
Circulating carboxy-terminal fragments are filtered by the kidney, but are subsequently broken down into even smaller fragments during tubular reuptake. No studies have so far been performed in patients with severe hepatic impairment. The pharmacokinetics of parathyroid hormone in patients with severe chronic kidney disease (creatinine clearance of less than 30 ml/min) has not been investigated either. Pharmaceutical particulars
Preotact is delivered in a two chamber, glass ampoule. One chamber contains the active substance in the form of a white powder (with excipients: mannitol, citric acid monohydrate, NaCl, NaOH, HCl). And the other contains the solvent; water for injection. The powder is mixed with the solvent when the ampoule is inserted into the injection device. Storage and shelf-life
The mixed solution is stable for 28 days when stored between 2 and 8 °C. During this 28-day period the mixed solution may be stored for up to 7 days at room temperature, allowing the patient the freedom to travel. Unmixed ampoules have a shelf-life of 30 months. The products should not be frozen and should be protected from light. See also
Teriparatide, another parathyroid hormone

References
External links
"Parathyroid hormone". Drug Information Portal. U.S. National Library of Medicine.