Adult: 5 mg once daily or 35 mg once weekly. Re-evaluate therapy periodically according to individual benefits and potential risks.
Oral Osteoporosis
Adult: In males and in postmenopausal females: 10 mg once daily or 70 mg once weekly. Re-evaluate therapy periodically according to individual benefits and potential risks.
Oral Paget's disease of bone
Adult: 40 mg once daily for 6 months; may be repeated if necessary after 6-month post-treatment evaluation period.
Oral Corticosteroid-induced osteoporosis
Adult: 5 mg once daily or 10 mg in postmenopausal women not receiving HRT.
Renal Impairment
CrCl (mL/min)
Dosage
<35
Not recommended.
Administration
Should be taken on an empty stomach. Take w/ a full glass of plain water at least 30 min before the 1st food/drink/medication of the day & remain in sitting/upright position for at least 30 min. Swallow whole, do not chew/crush.
Reconstitution
Effervescent tab: Dissolve tab in a half glass of plain water (at least 120 mL). Once effervescence stops, wait ≥5 minutes and stir the buffered solution for approx 10 seconds if the tab does not dissolve completely until it is clear to slightly cloudy.
Contraindications
Hypocalcaemia, abnormalities of the oesophagus which delay oesophageal emptying (e.g. stricture, achalasia); increased risk of aspiration (effervescent tab, oral solution). Patient who is unable to stand or sit upright for at least 30 minutes.
Special Precautions
Patient with active upper gastrointestinal problems (e.g. dysphagia, other oesophageal disease, ulcers, duodenitis, gastritis, recent history of major gastrointestinal disease, known Barrett’s oesophagus), risk factors for developing osteonecrosis of the jaw (e.g. cancer, history of dental disease, periodontal disease) or external auditory canal (e.g. infection, trauma); other disorders affecting mineral metabolism (e.g. hypoparathyroidism, vitamin D deficiency). Renal impairment CrCl <35 mL/min. Pregnancy and lactation.
Adverse Reactions
Significant: Local irritation of the upper gastrointestinal mucosa, oesophageal reactions (e.g. oesophageal ulcers, oesophagitis, oesophageal erosions); decreased serum Ca and phosphate; severe bone, joint and/or muscle pain; atypical subtrochanteric and diaphyseal femoral fractures (prolonged use), osteonecrosis of the jaw and external auditory canal. Rarely, gastric and duodenal ulcers, Stevens-Johnson syndrome, toxic epidermal necrolysis. Ear and labyrinth disorders: Vertigo. Gastrointestinal disorders: Abdominal pain, abdominal distension, acid regurgitation, constipation, diarrhoea, dyspepsia, flatulence. General disorders and administration site conditions: Asthenia, peripheral oedema. Musculoskeletal and connective tissue disorders: Joint swelling. Nervous system disorders: Dizziness, headache. Skin and subcutaneous tissue disorders: Alopecia, pruritus.
Ensure adequate intake of Ca and vitamin D; take supplements if dietary intake is insufficient.
Monitoring Parameters
Assess serum Ca (prior to and during treatment) and 25-hydroxyvitamin D for all indications; correct hypocalcaemia before initiation of therapy. Osteoporosis: Evaluate serial BMD at baseline and every 1-3 years during treatment then every 2-4 years during a drug holiday. In patients on combined alendronate and glucocorticoid therapy: Assess BMD at the beginning of glucocorticoid therapy then after 6-12 months; then every 2-3 years if patient continues to have significant osteoporosis risk. Monitor height and weight (annually), biochemical markers of bone turnover (e.g. fasting serum C-terminal cross-linked telopeptide [CTX] or urinary N-terminal telopeptide [NTX]) at baseline, 3 months, and 6 months; signs of chronic back pain. Monitor possible malabsorption. Perform routine dental check-ups. Paget’s disease: Monitor serum total alkaline phosphatase at 6-12 weeks and potentially at 6 months; then at approx 6-12-month intervals following treatment completion; symptoms of pain. Monitor specific biochemical markers of bone turnover (e.g. NTX, serum β-CTX, serum procollagen type 1 N-terminal propeptide [P1NP]) in patients with abnormal liver or biliary tract function or when early assessment of treatment is needed.
Overdosage
Symptoms: Hypophosphataemia, hypocalcaemia, upper gastrointestinal effects (e.g. heartburn, upset stomach, gastritis or ulcer, oesophagitis). Management: Do not induce vomiting to prevent oesophageal irritation; remain patient in a fully upright position. Milk or antacids may be given to bind alendronate.
Drug Interactions
Antacids, Ca supplements or other oral medications containing multivalent cations may interfere with the absorption of alendronic acid. Increased risk of gastrointestinal irritation with aspirin or NSAIDs. Decreased bioavailability with levothyroxine.
Food Interaction
Food and beverages (including mineral water) may reduce the absorption of alendronic acid.
Lab Interference
May interfere with diagnostic imaging agents in bone scans.
Action
Description: Alendronic acid is an aminobisphosphonate which inhibits the activity on osteoclasts or osteoclast precursors, thus decreasing the rate of bone resorption leading to an indirect increase in bone mineral density. Its mechanism of action in Paget’s disease is characterised by inhibition of resorption leading to an indirect decrease in bone formation but the newly formed bone has a more normal structure.
Synonym: alendronate. Pharmacokinetics: Absorption: Poorly absorbed from the gastrointestinal tract. Bioavailability: 0.6% (fasted state). Food and products containing calcium or polyvalent cations may decrease absorption. Distribution: Volume of distribution: 28 L (exclusive of bone). Plasma protein binding: Approx 78%. Metabolism: Not metabolised. Excretion: Via faeces (as unabsorbed drug); urine. Elimination half-life: >10 years.
Chemical Structure
Alendronic acid Source: National Center for Biotechnology Information. PubChem Database. Alendronic acid, CID=2088, https://pubchem.ncbi.nlm.nih.gov/compound/Alendronic-acid (accessed on Jan. 20, 2020)
Storage
Store between 15-30°C. Protect effervescent tab from moisture.
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