Total Volume of Forteo for 365 Days of Treatment
The total volume of Forteo (teriparatide) needed for a full year of treatment at 20 mcg daily is 7.3 mL.
Calculation Based on FDA Drug Information
According to the FDA drug label for teriparatide (Forteo), the medication is supplied as follows 1:
- Concentration: 250 mcg/mL
- Each pen delivers 20 mcg per dose
- Each pen contains 2.48 mL of solution
- Each pen provides 28 daily doses
To calculate the total volume needed for 365 days:
- Daily dose: 20 mcg
- Concentration: 250 mcg/mL
- Volume per day: 20 mcg ÷ 250 mcg/mL = 0.08 mL/day
- Total volume for 365 days: 0.08 mL/day × 365 days = 29.2 mL
However, since Forteo is supplied in pre-filled pens that each deliver 28 doses:
- Number of pens needed: 365 days ÷ 28 days/pen = 13.04 pens (rounded to 14 pens)
- Actual volume used from pens: 14 pens × 0.08 mL/dose × 28 doses/pen = 31.36 mL
Clinical Context and Administration
Teriparatide (Forteo) is indicated for treatment of:
- Postmenopausal women with osteoporosis at high risk for fracture
- Men with primary or hypogonadal osteoporosis at high risk for fracture
- Men and women with osteoporosis associated with sustained systemic glucocorticoid therapy 1
The American Family Physician guidelines indicate that teriparatide should be used for patients with severe osteoporosis or those who cannot tolerate other treatments 2.
Important Administration Considerations
- Teriparatide is administered as a subcutaneous injection into the thigh or abdominal region
- Each pre-filled pen delivers exactly 20 mcg per dose
- The medication should be stored in the refrigerator
- Patients should be instructed to take supplemental calcium and vitamin D if dietary intake is inadequate 1
- Treatment duration should not exceed 2 years during a patient's lifetime unless the patient remains at or has returned to having a high risk for fracture 1
Practical Dispensing Information
For a full year of therapy, patients would need:
- 13 complete pens (364 days)
- Plus 1 additional dose from a 14th pen
- Each pen contains 28 doses (2.48 mL total)
- Total actual volume used: 7.3 mL (0.08 mL × 365 doses)
Note that in practice, prescriptions are typically written for complete pens rather than specific volumes, since the medication comes in pre-filled, fixed-dose delivery devices.