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Alendronate

Class
Indications
  • Treatment and prevention of osteoporosis in women
  • Paget's disease of bone
  • To reduce hypercalcemia in tumor-induced bone disease
Administration/Absorption
  • Mean oral bioavailability of alendronate in women was 0.7%
Dosage
  • Prophylaxis of osteoporosis in women: 5–10 mg daily or 35–70 mg weekly
  • Paget's Disease: 40 mg daily for 6 months
Distribution
  • 78% protein bound
  • VOD 28 L
Mechanism
  • Based partly on its affinity for hydroxyapatite, which is part of the mineral matrix of bone
  • Also targets farnesyl pyrophosphate (FPP) synthase
    • Acts as a analogue of isoprenoid diphosphate lipids, thereby inhibiting FPP synthase
      • An enzyme in the mevalonate pathway
    • Inhibition of this enzyme in osteoclasts prevents the biosynthesis of isoprenoid lipids (FPP and GGPP)
      • Essential for the post-translational farnesylation and geranylgeranylation of small GTPase signalling proteins
    • This activity inhibits osteoclast activity and reduces bone resorption and turnover
Excretion
  • There is no evidence that alendronate is metabolized in humans or animals
  • Approximately 50% excreted in the urine within 72 hours
Side effects
  • Can damage the esophagus
    • By toxicity from the medication itself
    • Also by nonspecific irritation secondary to contact between the pill and the esophageal mucosa
  • Rash
  • Osteonecrosis of the Jaw
  • Rare instances of auditory hallucinations and visual disturbances
Interactions
  • Milk, diet, and drugs containing high amounts of calcium, magnesium or aluminium decrease absorption
  • The combination of NSAIDs and alendronate may increase the risk of gastric ulcers
Contraindications
  • Acute inflammations of the gastrointestinal tract (esophagitis, gastritis, ulcerations)
  • Clinically manifest osteomalacia
  • Certain malformations and malfunctions of the esophagus (strictures, achalasia)
  • Inability to stand, walk, or sit for 30 minutes after oral administration
  • Renal impairment with a creatinine clearance below 30ml/min
  • Hypersensitivity to alendronate or another ingredient
  • Hypocalcemia
  • Pregnancy and breastfeeding
  • Patients below 18 yrs. of age, as no clinical data exists
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