What is the recommended treatment and dosage for Fosamax (alendronate) in patients with osteoporosis?

Fosamax (Alendronate) Treatment for Osteoporosis

For treating established osteoporosis, prescribe alendronate 70 mg once weekly, which is the standard evidence-based regimen that maximizes convenience while maintaining therapeutic efficacy. 1, 2, 3

Standard Dosing Regimens

Treatment of Established Osteoporosis

• 70 mg once weekly is the recommended dose for postmenopausal women and men with osteoporosis 1, 2, 3
• This weekly regimen is therapeutically equivalent to 10 mg daily dosing, producing identical increases in bone mineral density (5.1% vs 5.4% at lumbar spine after one year) 3, 4
• Alternative daily dosing of 10 mg is available but offers no advantage over weekly dosing 3

Prevention of Osteoporosis

• 35 mg once weekly for postmenopausal women at risk but without established osteoporosis 1, 2
• Alternative daily dosing of 5 mg is available for prevention 2

Combination Formulation

• Alendronate/cholecalciferol (Fosamax Plus D) 70 mg plus 2,800 IU or 5,600 IU vitamin D once weekly is an option that ensures adequate vitamin D supplementation 2

Essential Supplementation Requirements

All patients must receive adequate calcium and vitamin D supplementation, as failure to do so significantly reduces treatment efficacy. 2

• Calcium: 1,000-1,200 mg daily for all patients 5, 2
• Vitamin D: 800-1,000 IU daily (some guidelines recommend up to 800 IU) 5, 2
• Check serum 25-hydroxy vitamin D levels before initiating therapy; target level ≥30 ng/mL 2
• For vitamin D deficiency (25-OH vitamin D <30 ng/mL), prescribe ergocalciferol 50,000 IU weekly for 8 weeks, then recheck 2

Critical Contraindications and Precautions

Absolute Contraindications

• Renal impairment with GFR <35 mL/min/1.73 m² - do not prescribe alendronate in this population 1, 2
• Abnormalities of the esophagus that delay esophageal emptying 2
• Inability to stand or sit upright for at least 30 minutes 2
• Hypocalcemia (must be corrected before initiating therapy) 2

Administration Instructions to Prevent Esophageal Complications

• Take with a full glass (6-8 oz) of plain water only, after an overnight fast 6
• Remain upright (sitting or standing) for at least 30 minutes after taking the medication 2
• Take at least 30 minutes before the first food, beverage, or other medication of the day 7, 6
• Do not lie down until after eating the first meal of the day 2

Special Populations

Men with Osteoporosis

• 70 mg once weekly is equally effective in men with hypogonadal or idiopathic osteoporosis 3
• At one year, produces 2.8% increase in lumbar spine BMD and 1.9% increase at femoral neck 3

Glucocorticoid-Induced Osteoporosis

• 5 mg daily is the standard dose for patients on ≥7.5 mg/day prednisone or equivalent 5, 3
• 10 mg daily may be considered for postmenopausal women not receiving estrogen therapy 3
• Initiate therapy at the start of glucocorticoid treatment for patients at high fracture risk 2

Cancer Patients on Androgen Deprivation Therapy

• 70 mg once weekly when 10-year probability of hip fracture is ≥3% or major osteoporotic fracture is ≥20% using FRAX algorithm 5
• Consider ADT as "secondary osteoporosis" when calculating FRAX scores 5
• Obtain baseline DEXA scan before starting ADT in men at increased fracture risk 5

Duration of Therapy and Monitoring

Treatment Duration

• Consider drug holidays after 5 years of continuous therapy due to concerns about rare adverse effects with long-term use, though fracture protection may persist for up to 5 years after discontinuation 2
• The optimal duration is not definitively established, but trends favor interrupting therapy after 5-10 years 2

Monitoring Strategy

• Repeat BMD measurement after 1-2 years of initiating therapy 8
• Follow-up DEXA scan after 1 year is recommended by the International Society for Clinical Densitometry 5
• Biochemical markers of bone turnover are not recommended for monitoring response 5

Rare but Serious Adverse Effects

Osteonecrosis of the Jaw (MRONJ)

• Incidence: <1 to 28 cases per 100,000 person-years 2
• Risk increases with duration of therapy beyond 2 years 2

Atypical Femoral Fractures

• Incidence: 3.0 to 9.8 cases per 100,000 patient-years 2
• Requires careful risk-benefit assessment in long-term users 2

Clinical Efficacy Data

Alendronate reduces vertebral fracture risk by 47-48% and multiple vertebral fractures by 87-90% in postmenopausal women with osteoporosis. 3

• Hip fracture risk reduction of 44-47% in women with existing vertebral fractures 3
• Increases lumbar spine BMD by 5-8% over 1-3 years 3
• Bone histology remains normal with no evidence of impaired bone quality 3

Common Pitfalls to Avoid

• Never prescribe alendronate to patients with GFR <35 mL/min/1.73 m² - this is a critical safety issue 1, 2
• Do not initiate therapy without correcting hypocalcemia first - risk of severe hypocalcemia 2
• Ensure patients understand proper administration technique - improper dosing significantly increases risk of esophageal complications 2
• Do not discontinue calcium and vitamin D supplementation - this reduces treatment efficacy 2
• Avoid concurrent use with proton pump inhibitors when possible - PPIs decrease calcium absorption and may increase fracture risk 8