Onely Einmal Wöchentlich (Alendronic Acid)

Alendronic acid is indicated for conditions affecting bone remodeling and mineral density.

• Osteoporosis: reduces the risk of vertebral and hip fractures in post‑menopausal women and men.
• Paget’s disease of bone: normalises elevated bone turnover markers and improves radiographic appearance.
• Osteopenia with high fracture risk: helps maintain bone mineral density and lowers fracture incidence.
• Glucocorticoid‑induced osteoporosis: mitigates bone loss associated with long‑term corticosteroid therapy.
• Secondary osteoporosis: supports bone strength in patients with endocrine or metabolic disorders that predispose to fractures.

• Alendronic acid binds selectively to hydroxyapatite crystals at sites of active bone resorption. When osteoclasts attach to the drug‑coated bone surface, the compound is internalised, inhibiting farnesyl pyrophosphate synthase within the mevalonate pathway. This disruption impairs osteoclast maturation and induces apoptosis, leading to decreased bone resorption and a net increase in bone mineral density.

Adverse reactions to alendronic acid may range from mild to serious and are reported in clinical use.

Common Side Effects

• Gastrointestinal irritation: dyspepsia, abdominal pain, or heartburn.
• Musculoskeletal pain: transient bone, joint or muscle aches.
• Esophageal ulceration: irritation or ulcer formation when tablets are not taken with sufficient water.
• Nausea or vomiting: occasional upset stomach.
• Headache: mild to moderate intensity.

Serious or Rare Side Effects

• Osteonecrosis of the jaw (ONJ): exposed bone in the jaw, often after dental procedures.
• Atypical femoral fractures: low‑energy fractures of the subtrochanteric region.
• Severe esophageal erosion or perforation.
• Acute phase reactions: fever, myalgia, or flu‑like symptoms after the first dose.
• Hypocalcaemia: low serum calcium levels, especially in patients with vitamin D deficiency.

When prescribing alendronic acid, clinicians should consider several safety measures.

• Renal function: assess baseline kidney function and avoid use in severe impairment.
• Gastro‑esophageal disease: evaluate for active ulcer disease or strictures before initiating therapy.
• Calcium and vitamin D status: ensure adequate supplementation to reduce hypocalcaemia risk.
• Dental health: advise patients to complete any invasive dental work before starting treatment.
• Concomitant medications: review for drugs that may affect absorption or increase esophageal irritation.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and heat.

Alendronic acid may interact with several medicines, altering its absorption or increasing adverse effects.

Major Interactions (Avoid)

• Antacids containing calcium, magnesium or aluminium: reduce oral absorption of alendronic acid.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of gastrointestinal ulceration.
• Corticosteroids: synergistic effect on gastric mucosa, raising ulcer risk.

Moderate Interactions (Monitor Closely)

• Proton pump inhibitors (PPIs): may diminish drug efficacy by raising gastric pH.
• Loop diuretics: potentiate hypocalcaemia.
• Thyroid hormones (levothyroxine): may interfere with absorption if taken concurrently.