Growth hormone OK'd for adults and kids

July 10, 2006

After almost three years, the Food & Drug Administration has approved Omnitrope (somatropin, Sandoz) as a follow-on version of Pfizer's Genotropin. "Its approval is beneficial for everyone. It also increases competition in the growth hormone market, which will hopefully reduce the price of growth hormones," stated Anita Siu, Pharm.D. and clinical neonatal/ pediatric pharmacotherapy specialist and assistant clinical professor at the Ernest Mario School of Pharmacy, Rutgers, the state university of New Jersey.

Omnitrope is a polypeptide hormone of recombinant DNA origin synthesized in a strain of E. coli that has been modified by the addition of the gene for human growth hormone. The drug is indicated for the long-term treatment of pediatric patients with growth failure due to an in-adequate secretion of endogenous growth hormone and for long-term replacement therapy in adults with growth hormone deficiency (GHD).

Omnitrope was approved through section 505(b)(2) of the Food, Drug & Cosmetic Act. It is characterized as a follow-on protein product similar to one already approved, with its safety and effectiveness based on the approved product. It is not rated therapeutically equivalent to or even substitutable for any other approved human growth hormone product.

The safety and efficacy of Omnitrope, compared with another somatropin comparator, showed similar effects on growth during nine months of treatment. The most frequently reported adverse events in pediatric patients were hypothyroidism, elevated HbA1c, eosinophilia, hematoma, headache, hypertriglyceridemia, and leg pain.

Somatropin-treated adults had beneficial changes in body composition compared with placebo at the end of the six-month treatment period. Lean body mass, total body water, and lean/fat ratio increased; total body fat mass and waist circumference decreased. Most adverse events reported were mild to moderate fluid retention, including arthralgia; pain and stiffness in the extremities; peripheral edema; myalgia; paresthesia; and hypoesthesia. Pfizer recommends that patients have periodic thyroid function tests and be treated with thyroid hormone if hypothyroidism develops.

The dosage needs to be individualized for each patient. In pediatric patients, the recommended dose is 0.16-0.24 mg/kg/ week. In adults, the recommended dosage at the start of therapy should not exceed 0.04 mg/kg/week. The dosage may be increased at four- to eight-week intervals, with a maximum of 0.08 mg/ kg/week. The weekly dose should be divided into daily subcutaneous injections, preferably in the evening. The preferred administration sites are thigh, buttocks, and abdomen, rotating the site to prevent lipoatrophy.

Omnitrope is supplied in 1.5-mg or 5.8-mg vials. The diluent for 1.5-mg vials is sterile water for injection; the diluent for 5.8- mg vials is bacteriostatic water for injection containing benzyl alcohol. The drug is light-sensitive and should be refrigerated. Omnitrope 1.5 mg should be used within 24 hours after reconstitution, and Omnitrope 5.8 mg within three weeks of reconstitution when stored under refrigeration.

THE AUTHOR is a writer based in New Jersey.

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