Forteo (Teriparatide)

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Vol. 11 •Issue 9 • Page 18
Drug Data

Forteo (Teriparatide)

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Forteo brand of teriparatide (rDNA origin) injection, from Eli Lilly and Co., was approved by the FDA in December 2002 for the treatment of osteoporosis in postmenopausal women who are at high risk of fracture. Teriparatide is also indicated and FDA-approved for the treatment of primary or hypogonadal osteoporosis in men at high risk for fractures.1-4 The drug also has a non-FDA-approved indication for hypoparathyroidism.4

Pharmacology

The pharmacologic action of teriparatide is mediated through the binding of the drug to specific high-affinity cell-surface receptors. This action results in increase in skeletal mass, markers of bone formation and resorption, and bone strength.1-4

Dosage and Administration

The normal dose of teriparatide is 20 µg once daily via subcutaneous injection in the thigh or abdomen. The length of treatment should not exceed two years. Because of teriparatide’s potential to cause orthostatic hypotension, it is recommended that the patient should sit or lie down for the administration of the initial dose to avoid unexpected falling. Teriparatide is available as a 3 mL prefilled pen with a concentration of 250 µg/mL.1-4

Adverse Drug Reactions

Chest pain, syncope, dizziness, depression, vertigo, rash, hypercalcemia, nausea, dyspepsia, vomiting, arthralgia, weakness, rhinitis, pharyngitis, dyspnea and pneumonia were the most common side effects reported in clinical trials, with incidences ranging from 1% to 10% of subjects.1-4

Interactions

Use caution in patients taking digoxin, since teriparatide causes increased serum calcium levels, leading to digitalis toxicity in patients concomitantly taking digoxin and teriparatide. Clinical trials reported an increase of 2% in serum calcium levels and an increase 37% in 24-hour urine calcium levels when intravenous furosemide (20 mg to 100 mg) was given to healthy patients and patients with various stages of renal impairment taking teriparatide.1-4 However, this result did not seem to be clinically significant. Teriparatide is contraindicated in patients with Paget’s disease.2-4

Patient Education

• Patients should sit or lie down for the initial dose of teriparatide in case of orthostatic hypotension.

• Patients should contact their provider if any signs of hypercalcemia occur, such as nausea, vomiting, muscle weakness or constipation.

• Patients can take teriparatide without regard to food.

• Teriparatide should be injected in the thigh or abdomen.

• Teriparatide should be injected shortly after removal from the refrigerator.

• Teriparatide should not be used if it is cloudy or has solid particles in it.

• Patients should be instructed on how to correctly use the pen for injection.1-4

Place in Therapy

Drugs such as conjugated estrogens (e.g., Premarin), bisphosphonates (such as alendronate and risedronate), raloxifene and calcitonin have been approved for the treatment and prevention of osteoporosis. Premarin prevents bone loss through estrogen-like effects. However, HRT has been associated with an increased risk of thrombosis, breast cancer and heart disease.5

Risedronate has fewer gastrointestinal side effects and has proven to be more potent than alendronate. However, compliance is an issue with this class of agents. They must be taken after an overnight fast in the morning with six to eight ounces of water.5

Raloxifene offers the estrogen-like effects without the risk associated with HRT. However, it does increase the risk of deep thrombosis.5

Calcitonin is safer to use, but it has proven to be less effective than the aforementioned agents for the treatment of osteoporosis.5,6

Teriparatide is relatively expensive compared with the other agents, costing approximately $600 for a month supply. Despite the high cost of teriparatide, it is the only agent that directly stimulates the formation of new bone rather than just decreasing the progression of bone loss. It also has fewer side effects. If cost is an issue, it should be considered for patients who fail therapy with the other agents.5,6

Yolanda D. Williams is a 2003 doctor of pharmacology candidate at Hampton University in Hampton, Va. Miriam S. Ansong and Maurice W. Landers Jr. are assistant professors of pharmacy practice in the school of pharmacy at Hampton University.

References

1. Osteoporosis Management Quick Reference. Clinical Reference Online 2002. Hudson, Ohio: Lexi-Comp Inc. Available at: http://www.crlonline.com. Accessed January 10, 2003.

2. Forteo [package insert]. Indianapolis, Ind: Eli Lilly and Co; 2002.

3. Drug Facts and Comparisons 2003. St. Louis, Mo: Facts and Comparisons; 2002:333a-333c.

4. Teriparatide. In: Reents S, ed. Clinical Pharmacology 2002. Tampa, Fla: Gold Standard Multimedia Inc. Available at: http://cp.gsm.com. Accessed January 10, 2003.

5. Pharmacologic options. National Osteoporosis Foundation Web site. Available at: http://nof.org/physguide/pharmacologic.htm. Accessed February 1, 2003.

6. Alendronate, risedronate, raloxifene and calcitonin. In: Reents S, ed. Clinical Pharmacology 2002. Tampa, Fla: Gold Standard Multimedia Inc. Available at: http://cp.gsm.com. Accessed February 3, 2003.

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