What are the side effects of Forteo (teriparatide)?

Forteo (Teriparatide) Side Effects

Forteo causes common gastrointestinal symptoms, headaches, and hypercalcemia, with most side effects being mild and manageable, though patients should be monitored for transient hypotension after initial doses and the medication carries a black box warning for osteosarcoma risk based on animal studies.

Most Common Side Effects

Gastrointestinal symptoms are the most frequently reported adverse effects:

• Upper GI symptoms occur significantly more often than placebo (OR 3.26), including nausea, vomiting, and gastritis 1
• Nausea is particularly common, occurring in approximately 14% of patients 2
• Pain and joint aches are also frequently reported 2

Headache occurs with increased frequency (OR 1.46) compared to placebo 1

Musculoskeletal symptoms include:

• Leg cramps 1, 3, 4
• Arthralgias 5
• Generalized bone pain (rare but reported) 6

Metabolic and Laboratory Abnormalities

Hypercalcemia is the most significant metabolic effect:

• Occurs with markedly increased frequency (OR 12.9) compared to placebo 1
• Approximately 3% of women and 1% of men develop transient hypercalcemia on consecutive measurements 2
• Symptoms may include nausea, vomiting, constipation, low energy, or muscle weakness 2

Renal effects:

• Increased risk of renal side effects (OR 2.36) 1
• Hypercalciuria occurs more frequently (OR 2.44), which may worsen kidney stones in susceptible patients 1
• Serum uric acid increases in 3% of patients, though this rarely causes clinical gout or urolithiasis 2

Cardiovascular Effects

Transient hypotension and orthostatic symptoms:

• Dizziness, fast heartbeat, or lightheadedness can occur within 4 hours of injection, particularly with the first few doses 2, 7
• Blood pressure may decrease significantly 30-60 minutes after injection 7
• Patients should sit or lie down during initial injections to prevent falls 2
• This effect is usually transient and resolves within hours 2

Palpitations have been reported 1, 3

Serious Adverse Events

Osteosarcoma (Black Box Warning):

• Rat studies showed dose-dependent osteosarcoma development, leading to FDA black box warning 2, 5
• However, postmarketing surveillance over 9 years found no cases of osteosarcoma attributable to teriparatide use in humans 1
• Two large observational studies identified only 3 cases among 379,283 users and zero cases among 153,316 users, suggesting similar risk to non-users 2
• Patients should report persistent bone pain or new lumps under the skin 2

Treatment discontinuation:

• Withdrawal due to adverse events occurs more frequently than placebo (ARD 17-127 more events per 1000 patients at 24-36 months) 1
• Common reasons include nausea, dizziness, vomiting, headache, palpitations, and leg cramps 1

Injection Site Reactions

• Pain, swelling, and bruising at injection sites have been reported 2

Allergic Reactions (Rare)

Postmarketing reports include:

• Anaphylactic reactions 2
• Drug hypersensitivity 2
• Angioedema and urticaria 2
• Oro-facial edema 2

Important Clinical Considerations

Monitoring requirements:

• Calcium levels should be monitored, especially in patients with history of kidney stones 2
• Patients with glucocorticoid-induced osteoporosis may have slightly higher rates of pneumonia (6% vs 3%) and dyspnea (6% vs 3%) 2

Duration limitations:

• Teriparatide should not be used for more than 2 years over a patient's lifetime unless high fracture risk persists 2
• Must be followed by antiresorptive therapy to prevent rapid bone loss 1, 3

Contraindications where side effects would be particularly concerning:

• Paget's disease, prior skeletal radiation, bone metastases, or open epiphyses 3