Bisphosphonate·Endocrinology - Thyroid & Bone

Alendronate

Postmenopausal osteoporosis, male osteoporosis, glucocorticoid-induced osteoporosis

Authority requiredPBSBISPHOSPHONATEFosamax, Fosamax Plus (combo with Colecalciferol)10 mg tablet+2

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At a glance

Max Dose

70 mg/week

Caution: Half-life

10 YEARS

Caution: Esophagitis

HIGH RISK

Empty Stomach

MANDATORY

Cautions

Avoid / Cautions

Inability to stand/sit upright for 30 minutes. Esophageal stricture/achalasia. Hypocalcemia. Pregnancy Category B3. Incorporates into bone and could theoretically leach out during future pregnancies, affecting fetal skeleton.

Where it stands

Rapid Summary

Overview

Potent antiresorptive nitrogenous bisphosphonate. The first-line oral therapy for osteoporosis. Binds permanently to bone to prevent osteoclast destruction.

Clinical Focus

Has < 1% oral bioavailability. Must be taken exactly as prescribed (fasting, upright, water only) or it will completely fail to absorb and ulcerate the esophagus.

Bottom Line

Alendronate is the first-line oral bisphosphonate for osteoporosis prevention and treatment, but must be taken upright with water on an empty stomach and carries risk of oesophageal ulceration and rare osteonecrosis of the jaw.

Formulation & Access

Brand Names

Fosamax, Fosamax Plus (combo with Colecalciferol)

Oral Routes

Tablets (10 mg, 70 mg).

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Postmenopausal osteoporosis, male osteoporosis, glucocorticoid-induced osteoporosis.

Clinical Place

First-line agent. Proven to significantly reduce vertebral and non-vertebral fracture risk.

Quick reference

Class & Role

Bisphosphonate — Potent antiresorptive nitrogenous bisphosphonate.

Route / Formulation

Tablets (10 mg, 70 mg). (Fosamax, Fosamax Plus (combo with Colecalciferol))

Usual Dose & Max

PO 70 mg ONCE WEEKLY. Max 70 mg/week (Osteoporosis) or 40 mg/day (Paget's disease).

Key Indication Doses

Osteoporosis (Treatment/Prophylaxis): PO 70 mg ONCE WEEKLY. Glucocorticoid-Induced Osteoporosis: PO 70 mg ONCE WEEKLY. Renal Impairment: Avoid entirely if eGFR < 35 (risk of severe accumulation).

Best Uses

Key Risks

Gastrointestinal: Severe erosive esophagitis, esophageal ulcers, strictures. Musculoskeletal: Osteonecrosis of the jaw (ONJ), atypical femoral fractures (associated with use > 5 years). Metabolic: Hypocalcemia (transient, usually asymptomatic).

Key Interactions

Calcium supplements, antacids, food, coffee, juice. ANY multivalent cation will bind the drug in the gut, dropping absorption to zero. Must separate by at least 2 hours.

Monitoring

Must be taken first thing in the morning, on an empty stomach, with a full glass of plain tap water. Patient MUST remain fully upright for 30 minutes. Dental check-up required prior to initiation due to ONJ risk. Routine DEXA scans every 1-2 years.

Clinical Pearl

Because it remains in the bone for a decade, patients who have been on Alendronate for 5 years (or 3 years if high-risk) should have a 'drug holiday' to prevent the bone from becoming brittle and suffering an atypical femoral fracture.

Access

Authority requiredFosamax, Fosamax Plus (combo with Colecalciferol)10 mg tablet

Brand: Fosamax, Fosamax Plus (combo with Colecalciferol)
PBS status: Authority required
Formulation: Tablets (10 mg, 70 mg).

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