What is the recommended dosage and frequency of Fosamax (Alendronate) for osteoporosis treatment?

Fosamax (Alendronate) Dosing for Osteoporosis

For treatment of established osteoporosis, the recommended dose is alendronate 70 mg once weekly, which is therapeutically equivalent to 10 mg daily dosing while offering superior convenience and adherence. 1, 2, 3

Treatment Dosing Regimens

Standard Treatment Options

• 70 mg once weekly is the preferred regimen for treating osteoporosis in postmenopausal women and men, demonstrating equivalent efficacy to daily dosing with lumbar spine BMD increases of 5.1-6.8% over 1-2 years 3, 4, 5
• 10 mg daily is an alternative treatment option, though less convenient for long-term adherence 3
• Alendronate/cholecalciferol combination (Fosamax Plus D) 70 mg plus 2,800-5,600 IU vitamin D once weekly is recommended by the American Academy of Family Physicians for comprehensive osteoporosis treatment 1

Prevention Dosing

• 35 mg once weekly for prevention of osteoporosis in postmenopausal women 1, 2
• 5 mg daily as an alternative prevention regimen 1, 2

Essential Concurrent Supplementation

All patients must receive adequate calcium and vitamin D supplementation to optimize therapeutic outcomes and prevent hypocalcemia. 1

• Calcium: 1,000-1,200 mg daily 1
• Vitamin D: 800-1,000 IU daily (or 400-800 IU in clinical trials) 1, 3
• Check serum 25(OH)D levels before starting therapy with target ≥30 ng/mL 1
• For vitamin D deficiency (25(OH)D <30 ng/mL): ergocalciferol 50,000 IU weekly for 8 weeks, then recheck 1

Special Populations

Glucocorticoid-Induced Osteoporosis

• 5 mg daily is strongly recommended for adults ≥40 years with moderate-to-high fracture risk receiving glucocorticoids, with demonstrated BMD increases of 2-4% at spine and hip sites 6, 3
• 10 mg daily may be preferred in postmenopausal women not on estrogen therapy, showing greater BMD increases (4.1% vs 1.6% at lumbar spine) 3

Men with Osteoporosis

• 70 mg once weekly or 10 mg daily, both demonstrating significant BMD increases (lumbar spine 2.8-5.3%, femoral neck 1.9-2.6%) regardless of age or gonadal function 3

Cancer Treatment-Induced Bone Loss

• 70 mg once weekly is effective for patients on androgen deprivation therapy, increasing hip BMD by 2.3% and spine BMD by 5.1% after 12 months 1

Critical Contraindications and Precautions

Absolute Contraindications

• GFR <35 mL/min/1.73 m² - alendronate is not recommended in significant renal impairment 1, 2
• Esophageal abnormalities that delay esophageal emptying 1
• Inability to stand or sit upright for at least 30 minutes 1
• Hypocalcemia (must be corrected before initiating therapy) 1

Administration Requirements

• Take in the fasting state with a full glass (6-8 oz) of plain water 3, 7
• Administer at least 30 minutes before first food, beverage, or other medication of the day 7, 8
• Patient must remain upright (sitting or standing) for at least 30 minutes after dosing 1

Duration of Therapy and Drug Holidays

• Consider drug holidays or dose reduction after 5 years of continuous therapy, as fracture protection may persist for up to 5 years after discontinuation 1
• The American Geriatrics Society recommends reassessing risk-benefit after 5-10 years due to rare adverse effects with long-term use 1
• For patients continuing beyond 5 years, careful monitoring for atypical femoral fractures (3.0-9.8 per 100,000 patient-years) and osteonecrosis of the jaw (<1-28 per 100,000 person-years) is warranted 1

Clinical Efficacy

• Vertebral fracture risk reduction: 47-56% in postmenopausal women with existing vertebral fractures 8
• Hip fracture risk reduction demonstrated in large randomized controlled trials 9, 8
• BMD increases are evident as early as 3 months and continue throughout treatment 3
• Bone histology remains normal with no impairment of bone quality 3, 8

Common Pitfalls to Avoid

• Do not administer to patients with GFR <35 mL/min/1.73 m² - this is a critical safety concern 2
• Never allow inadequate calcium/vitamin D supplementation - this reduces treatment efficacy and increases hypocalcemia risk 1
• Avoid abrupt discontinuation without considering sequential therapy - particularly important after denosumab, which requires bisphosphonate at 6-7 months to prevent rebound vertebral fractures 6
• Ensure proper administration technique to minimize esophageal adverse events 1, 8

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