Alendronic acid

Generic Name

Alendronic acid

Brand Names

Fosamax

Binosto (effervescent formulation)

Adrofos

Alendronate generics available in many countries

Drug Class

Bisphosphonate

Bone resorption inhibitor

Anti-osteoporotic agent

Mechanism of Action

Alendronic acid is a synthetic analog of pyrophosphate that binds to hydroxyapatite crystals in bone

It inhibits the activity of osteoclasts, the cells responsible for bone resorption

By reducing osteoclastic bone turnover, alendronic acid increases bone mineral density and prevents bone loss

Its action helps restore the balance between bone formation and resorption, particularly in postmenopausal women and elderly patients with osteoporosis

It remains in bone tissue for extended periods, providing long-lasting antiresorptive effects

Indications

Osteoporosis in Postmenopausal Women

First-line treatment to increase bone mass and reduce the incidence of vertebral and hip fractures

Osteoporosis in Men

Used to increase bone mass in men with primary or hypogonadal osteoporosis

Glucocorticoid-Induced Osteoporosis

Prevention and treatment in patients receiving systemic corticosteroids for ≥3 months

Paget’s Disease of Bone

Reduces bone turnover and relieves bone pain associated with Paget’s disease

Osteogenesis Imperfecta (Off-label in select cases)

May be used under specialist supervision

Dosing and Administration

Osteoporosis (Adults)

Once-weekly dosing: 70 mg orally once weekly

Once-daily dosing: 10 mg orally once daily

To be taken in the morning with plain water at least 30 minutes before food, beverage, or other medications

Patient must remain upright (sitting or standing) for at least 30 minutes after ingestion to prevent esophageal irritation

Paget’s Disease

40 mg orally once daily for 6 months

Retreatment may be considered after several months if relapse occurs

Renal Impairment

Not recommended in patients with creatinine clearance <35 mL/min

Use cautiously with monitoring in mild to moderate renal impairment

Hepatic Impairment

No dose adjustment necessary

Administration Instructions

Use only plain water (not mineral water, juice, coffee, or tea)

Swallow whole tablet with a full glass of water

Do not chew or suck the tablet

Do not lie down for at least 30 minutes and until after first food of the day

Pharmacokinetics

Oral bioavailability: <1% under fasting conditions

Peak serum concentration: 1 to 3 hours

Elimination half-life in bone: estimated to be over 10 years

Excreted unchanged in urine

Minimal hepatic metabolism

Contraindications

Esophageal abnormalities delaying emptying such as stricture or achalasia

Inability to sit or stand upright for at least 30 minutes

Hypocalcemia

Known hypersensitivity to alendronic acid or other bisphosphonates

Severe renal impairment (CrCl <35 mL/min)

Precautions

Ensure adequate calcium and vitamin D intake before initiating therapy

Caution in patients with active upper GI disorders (e.g. Barrett’s esophagus, ulcers)

Risk of osteonecrosis of the jaw, especially in cancer patients or those undergoing dental procedures

Risk of atypical femoral fractures with long-term use

Consider drug holiday after 3–5 years of treatment in low-risk patients

Monitor for musculoskeletal pain, which can be severe

Use caution in patients with poor oral hygiene or dental disease

Adverse Effects

Common

Gastrointestinal discomfort

Abdominal pain

Dyspepsia

Constipation or diarrhea

Nausea

Musculoskeletal pain

Headache

Acid reflux

Less Common

Esophagitis

Esophageal ulceration

Hypocalcemia

Skin rash

Alopecia

Dizziness

Serious

Osteonecrosis of the jaw

Atypical subtrochanteric or femoral shaft fractures

Severe musculoskeletal pain

Esophageal perforation or bleeding

Uveitis or scleritis

Allergic reactions

Pregnancy and Lactation

Pregnancy

Not recommended

Animal studies show skeletal abnormalities

Should only be used if potential benefit outweighs risk

Lactation

Not known whether alendronate is excreted in human milk

Use caution or consider alternative agents in breastfeeding women

Use in Special Populations

Geriatric

Commonly used in postmenopausal women

Effective and safe with monitoring

Evaluate fall risk and kidney function regularly

Renal Impairment

Avoid use in severe impairment

Monitor creatinine and adjust hydration

Pediatric

Limited use in children with severe bone disorders under specialist guidance

Not routinely recommended in general pediatric use

Drug Interactions

Calcium Supplements and Antacids

Reduce absorption of alendronic acid

Separate administration by at least 30–60 minutes

Iron, Magnesium, or Multivitamin Products

Interfere with absorption

Take at a different time of day

NSAIDs

Increased risk of GI irritation or ulceration

Use cautiously and monitor for upper GI symptoms

Aminoglycosides

Potential additive effect on lowering calcium levels

Monitor calcium closely

PPI or H2 Blockers

May mask GI symptoms or modify esophageal pH

Monitor for esophagitis or related symptoms

Monitoring Parameters

Bone mineral density (BMD) every 1–2 years

Serum calcium and 25-hydroxyvitamin D before initiation and periodically during treatment

Renal function at baseline and periodically

Signs of esophageal irritation or GI bleeding

Dental exam prior to initiation in high-risk patients

Formulations

Tablets: 5 mg, 10 mg, 35 mg, 40 mg, 70 mg

Effervescent tablets: 70 mg (Binosto – to be dissolved in water)

Combination formulations:

Alendronate + Cholecalciferol (Vitamin D3)

Patient Counseling Points

Take tablet in the morning on an empty stomach with plain water

Wait at least 30 minutes before consuming food, drinks, or other medications

Stay upright for at least 30 minutes after taking the dose

Report any chest pain, difficulty swallowing, or new hip or thigh pain

Maintain adequate calcium and vitamin D intake throughout therapy

Inform dentist of bisphosphonate use prior to invasive procedures

Report signs of jaw pain or loosening teeth

Do not take at bedtime or before rising

Keep hydrated to reduce risk of kidney side effects