AminobisphosphonateREQUIRES MONITORING

Alendronate

Fosamax · Alendronat Sandoz · Fosavance

First-line agent for osteoporosis and the best-documented fracture-preventing treatment in primary care. Efficacy for vertebral and hip fractures is well established, but depends on the patient's ability to follow the administration instructions and on adequate calcium and vitamin D status. After five years, treatment should be reviewed and is often paused.

BOXED WARNING

The tablet is strongly irritating to the mucous membranes. If taken lying down, with insufficient water, or by a patient with oesophageal stricture or achalasia, it can cause oesophagitis, ulcer, and stricture — hence the requirement to remain upright for 30 minutes after ingestion.

Dosing in adults

By indicationuppdaterad 2026-08-22

Indication	Regimen	Comment
Postmenopausal osteoporosis	70 mg orally once weekly	weekly dosing causes fewer oesophageal complaints than daily
Osteoporosis in men	70 mg orally once weekly	same dose as in women
Corticosteroid-induced osteoporosis	70 mg orally once weekly from initiation of steroid treatment	consider from ≥ 3 months of corticosteroid use
Concomitant supplementation	calcium 500–1000 mg and vitamin D 800 IU daily	correct deficiency before starting
Duration of treatment	review after 5 years, pause if residual risk is low	continue in very high fracture risk

Renal impairment

Not recommended at eGFR < 35 ml/min — insufficient evidence and risk of adynamic bone disease.

Hepatic impairment

No dose adjustment; not metabolised in the liver.

Children

Not used routinely in children; specialist use only in osteogenesis imperfecta.

Pitfall

Do not initiate alendronate before vitamin D deficiency is corrected — a bisphosphonate given to a patient with low 25-OH-vitamin D can precipitate symptomatic hypocalcaemia, and the treatment effect is lost regardless. Also avoid in patients who cannot sit or stand upright for 30 minutes after taking the tablet.

Pharmacokinetics

BIOAVAIL.: < 1 % fasting, near zero with food
t½ PLASMA: 1–2 hours
t½ SKELETON: > 10 years (bound to hydroxyapatite)
PROTEIN BINDING: approximately 78 %
METABOLISM: Not metabolised
EXCRETION: Renal, unchanged
ONSET: Bone density effect after 6–12 months
RESIDUAL EFFECT: Skeletal-bound effect persists 1–2 years after discontinuation

Adverse effects by frequency

≥ 10 %

Dyspepsia, abdominal pain, heartburn, musculoskeletal pain

1–10 %

Oesophagitis, dysphagia, headache, transient flu-like reaction at treatment initiation

< 1 %

Oesophageal ulcer and stricture, osteonecrosis of the jaw, atypical femoral fracture, uveitis, severe hypocalcaemia in untreated vitamin D deficiency