How Many Pens Needed for a 3-Month Supply of Forteo
For a standard 3-month supply of Forteo (teriparatide), patients need 3 pens, with each pen providing a 28-day supply of daily injections. 1
Understanding Forteo Pen Specifications
Forteo (teriparatide) is administered as a subcutaneous injection at a dose of 20 mcg once daily. Each Forteo pen is designed as a single-patient-use delivery device with the following specifications:
- Each pen contains 2.48 mL of solution
- Each pen delivers 20 mcg of teriparatide per dose daily
- Each pen provides up to 28 days of treatment 1
- Each mL contains 250 mcg of teriparatide (as a free base)
Calculation of Supply Needed
For a 3-month (approximately 90-day) supply:
- Number of pens needed = Total days ÷ Days per pen
- Number of pens needed = 90 days ÷ 28 days per pen
- Number of pens needed = 3.21 pens
Since partial pens cannot be prescribed and medication continuity is essential, 3 complete pens are required for a 3-month supply. This provides 84 days of treatment (28 days × 3 pens).
Important Considerations
- Forteo pens should be stored in the refrigerator when not in use
- Each pen should be discarded after 28 days of use, even if some medication remains
- Patients should be instructed to take supplemental calcium and vitamin D if dietary intake is inadequate 2
- Forteo is indicated for treatment of osteoporosis in postmenopausal women at high risk for fracture, men with primary or hypogonadal osteoporosis, and patients with glucocorticoid-induced osteoporosis 2
Clinical Pearls
- Forteo is limited to a lifetime maximum treatment duration of 2 years due to the potential risk of osteosarcoma
- The medication should be administered at approximately the same time each day
- Patients should be trained on proper injection technique and pen handling
- Unused medication should be properly disposed of after the 28-day usage period