Dosing and uses of Didronel (etidronate)
Adult dosage forms and strengths
tablet
- 200mg
- 400mg
Paget's Disease
Initial 5-10 mg/kg PO qDay not to exceed 6 months OR 11-20 mg/kg PO qDay not to exceed 3 months
Not to exceed 20 mg/kg/day
Retreatment should be initiated ONLY after at least 90 etidronate-free days AND evidence of active disease
Heterotopic Ossification
Total hip replacement
- 20 mg/kg PO qDay 1 month pre- and 3 months post-surgery (4 months total)
Spinal cord injury
- 20 mg/kg PO qDay for 2 weeks, THEN 10 mg/kg qDay for10 weeks (12 weeks total)
- Initiate treatment as soon as possible post-injury, preferably before diagnosis of heterotopic ossification
Renal Impairment
Safety and efficacy not established; administer a lower dose
Administration
Take 2 hours before food, milk, calcium-containing products, antacids, or multivalent metal ion-containing medication
Dose can be divided if gastric discomfort occurs
Other Indications & Uses
Off-label: prevention of PTH-induced bone resorption, myositis ossificans progressiva, calcinosis universalis
Pediatric dosage forms and strengths
Safety and efficacy not established
Didronel (etidronate) adverse (side) effects
1-10%
Convulsion
Fever
Hypocalcemia
Hypomagnesemia
Hypophosphatemia
Bone pain
Abnormal renal function
Frequency not defined
Amnesia
Confusion
Depression
Hallucination
Headache
Paresthesias
Alopecia
Rash
Altered taste
Gastritis
Glossitis
Hypocalcemia
Hypersensitivity reactions
Arthropathy
Fracture
Leg cramps
Nephrotoxicity
Renal insufficiency
Rare
- Esophageal cancer
- Peptic ulcer disease exacerbation
- Agranulocytosis
- Asthma exacerbation
Post-Marketing Reports
Skin: Alopecia
Hypersensitivity reactions, including angioedema, follicular eruption, macular rash, maculopapular rash, pruritus, epidermal necrolysis, Stevens-Johnson syndrome, and urticaria
Neuropsychiatric: Amnesia, confusion, depression, and hallucinations
Neurology: Paresthesias
Musculoskeletal: Arthropathies, including arthralgia and arthritis; bone fracture; osteomalacia
Hematology: Rare reports of agranulocytosis, pancytopenia, and a report of leukopenia with recurrence on rechallenge
Pulmonary: Exacerbation of asthma
Gastrointestinal: Exacerbation of existing peptic ulcer disease including perforation; esophagitis, glossitis
Warnings
Contraindications
Osteomalacia
Hypersensitivity
Esophagus abnormalities (eg, stricture, achalasia) that delay esophageal emptying
Cautions
Enterocolitis, renal impairment
May cause local irritation of upper GI mucosa
Potentially causes severe esophagitis, esophageal ulcers and erosions
Ensure adequate intake of calcium, vitamin d
Osteonecrosis of the jaw, can occur spontaneously and is generally associated with tooth extraction and/or local infection with delayed healing; known risk factors include invasive dental procedures (e.g., tooth extraction, dental implants, boney surgery), diagnosis of cancer, concomitant therapies (e.g., chemotherapy, corticosteroids, angiogenesis inhibitors), poor oral hygiene, and co-morbid disorders; risk of osteonecrosis of the jaw may increase with duration of exposure to bisphosphonates
Risk of severe bone, joint and/or muscle pain
At higher doses both resorption inhibition and bone growth inhibition increases
Esophageal cancer risk (July 21, 2011 FDA safety communication)
- Conflicting findings exist from studies evaluating the risk of esophageal cancer with oral bisphosphonates
- Esophagitis and other esophageal events have been reported, particularly in patients who do not follow the specific directions for use of oral bisphosphonates (eg, sit up or stand after administration, take with full glass of water)
- An ongoing review of data from published studies to evaluate whether use of oral bisphosphonate drugs is associated with an increased risk of cancer of the esophagus is currently being conducted by the FDA
- The FDA has not concluded that taking an oral bisphosphonate drug increases the risk of esophageal cancer
- There are insufficient data to recommend endoscopic screening of asymptomatic patients
- FDA will continue to evaluate all available data supporting the safety and effectiveness of bisphosphonate drugs and will update the public when more information becomes available
- Instruct patients to contact their healthcare provider if they develop symptoms of esophagitis (eg, swallowing difficulties, chest pain, new or worsening heartburn, trouble or pain when swallowing)
Pregnancy and lactation
Pregnancy category: C
Lactation: excretion in milk unknown; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Didronel (etidronate)
Mechanism of action
Bisphosphonate binds to hydroxyapatite crystals in bone and inhibits osteoclast-mediated bone resorption. Decreases mineral release and collagen or matrix breakdown in bone.
Pharmacokinetics
Half-Life elimination: 1-6 hr (PO)
Onset: Within 1-3 months of treatment
Duration: Effect can persist up to 12 months without continuous treatment
Bioavailability: 3%
Vd: 1.37 L/kg
Metabolism: None
Excretion: Primarily unchanged in urine, unabsorbed drug excreted in feces
