ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Bisphosphonate Pregnancy: Contraindicated — teratogenic in animal studies; bisphosphonates incorporate in bone and may persist. Use calcium and vitamin D in pregnancy instead.

Alendronic Acid (Alendronate)

Brand names: Fosamax, Binosto (effervescent)

Adult dose

Dose: Osteoporosis treatment: 70mg once weekly. Osteoporosis prevention (postmenopausal): 70mg once weekly. Glucocorticoid-induced osteoporosis: 70mg once weekly.
Route: Oral
Frequency: Once weekly (on the same day each week)
Max: 70mg once weekly
Administration: take on an empty stomach with a full glass of plain water (not mineral water, coffee, or juice) at least 30 minutes before first food, drink, or medication of the day. Remain upright (sitting or standing) for at least 30 minutes after dose — risk of oesophageal ulceration if patient lies down. Do not take within 2 hours of calcium supplements, antacids, or other oral drugs.

Paediatric dose

Route: Oral
Frequency: Weekly or daily
Max: Individualised
Not licensed for routine use in children. Used under specialist supervision in osteogenesis imperfecta and other metabolic bone diseases. Seek specialist paediatric endocrinology/metabolic bone opinion.

Dose adjustments

Renal

eGFR <35 mL/min/1.73m²: avoid — risk of accumulation; bisphosphonates renally cleared.

Hepatic

No dose adjustment required — not hepatically metabolised.

Clinical pearls

  • Prescribe calcium and vitamin D alongside bisphosphonate — must correct hypocalcaemia before starting (can precipitate severe symptomatic hypocalcaemia)
  • ONJ risk: advise dental check before starting long-term bisphosphonate; inform dentist of bisphosphonate use before any tooth extractions — consider drug holiday 3 months before invasive dental work
  • Drug holiday: after 5 years oral or 3 years IV bisphosphonate — consider reassessing fracture risk (NICE CG146); continued benefit without ongoing dosing due to incorporation in bone
  • Atypical femoral fracture: groin/thigh pain in long-term users is red flag — X-ray both femurs; characteristic transverse subtrochanteric fracture

Contraindications

  • eGFR <35
  • Oesophageal abnormalities (stricture, achalasia)
  • Inability to stand/sit upright for 30 minutes
  • Hypocalcaemia (must correct before starting)
  • Hypersensitivity to alendronate

Side effects

  • Oesophageal ulceration/erosion (serious — requires correct administration technique)
  • GI upset, dyspepsia, abdominal pain
  • Hypocalcaemia
  • Osteonecrosis of the jaw (ONJ — rare, risk with dental extractions)
  • Atypical femoral fractures (rare, long-term use >5 years)
  • Acute phase reaction (flu-like symptoms — mainly IV bisphosphonates)
  • Musculoskeletal pain

Interactions

  • Calcium supplements, antacids — chelate alendronate; reduce absorption — separate by ≥2 hours
  • NSAIDs — additive GI irritation
  • Ranitidine IV — increases alendronate bioavailability (not clinically relevant for oral use)

Monitoring

  • DEXA scan at baseline and every 2 years
  • Calcium and vitamin D (correct deficiency before starting)
  • Renal function (eGFR) before and periodically
  • Dental assessment
  • Symptom review (atypical bone pain)

Reference: BNFc; BNF 90; NICE CG146 (Osteoporosis); NICE TA160; FRAX tool. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Drugs
Pathways