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Bisphosphonate Pregnancy: 'There are no or limited amount of data from the use of alendronate in pregnant women. Studies in animals have shown reproductive toxicity. Alendronate given during pregnancy in rats caused dystocia related to hypocalcaemia. FOSAMAX should not be used during pregnancy.' Breast-feeding: 'It is unknown whether alendronate/metabolites are excreted in human milk. A risk to the newborns/infants cannot be excluded. FOSAMAX should not be used during breast-feeding.' Fertility: bisphosphonates are incorporated into the bone matrix and released over years; there is a theoretical risk of foetal harm, predominantly skeletal, if a woman becomes pregnant after completing a course of bisphosphonate therapy.

Alendronic Acid Weekly

Brand names: Fosamax Once Weekly, Binosto

Used in: Osteoporosis Falls & Frailty

This is the once-weekly oral alendronic acid formulation, an equivalent bisphosphonate regimen to daily dosing used for osteoporosis treatment and prevention, designed to improve adherence and reduce dosing frequency.

Adult dose

Dose: Osteoporosis: one 70 mg tablet once weekly
Route: oral — swallowed whole with a full glass of water (not less than 200 ml), on arising for the day and at least 30 minutes before the first food, beverage or medicinal product of the day
Frequency: once weekly, on the same chosen day each week
Max: 70 mg once weekly — the SPC gives a single recommended dosage and no higher dose
SCOPE: this dose is taken from the SPC for Fosamax Once Weekly 70 mg TABLETS. The effervescent alendronic acid 70 mg formulation also listed among this page's brands (Binosto) is a different licence with its own dispersion-in-water administration instructions, and is not covered by this source. VERBATIM SPC 4.2: 'The recommended dosage is one 70 mg tablet once weekly. Patients should be instructed that if they miss a dose of FOSAMAX Once Weekly, they should take one tablet on the morning after they remember. They should not take two tablets on the same day but should return to taking one tablet once a week, as originally scheduled on their chosen day. The optimal duration of bisphosphonate treatment for osteoporosis has not been established. The need for continued treatment should be re-evaluated periodically based on the benefits and potential risks of Fosamax on an individual patient basis, particularly after 5 or more years of use.' ADMINISTRATION, verbatim and load-bearing for safety: 'FOSAMAX must be taken at least 30 minutes before the first food, beverage, or medicinal product of the day with plain water only. Other beverages (including mineral water), food and some medicinal products are likely to reduce the absorption of alendronate... FOSAMAX should only be swallowed upon arising for the day with a full glass of water (not less than 200 ml). Patients should only swallow FOSAMAX whole. Patients should not crush or chew the tablet or allow the tablet to dissolve in their mouths because of a potential for oropharyngeal ulceration. Patients should not lie down for at least 30 minutes after taking FOSAMAX and until after the first food of the day. FOSAMAX should not be taken at bedtime or before arising for the day.' CALCIUM AND VITAMIN D: 'Patients should receive supplemental calcium and vitamin D if dietary intake is inadequate.' ELDERLY: 'In clinical studies there was no age-related difference in the efficacy or safety profiles of alendronate. Therefore no dosage adjustment is necessary for the elderly.' NOT STUDIED IN: 'FOSAMAX Once Weekly 70 mg has not been investigated in the treatment of glucocorticoid-induced osteoporosis.' UNDER 18s: 'The safety and efficacy of FOSAMAX in children less than 18 years of age has not been established. This medicinal product should not be used in children less than 18 years of age.' Some sections of the product information we used were incomplete — check the full SPC.

Dose adjustments

Renal

No dosage adjustment is necessary for patients with creatinine clearance greater than 35 ml/min. Alendronate is not recommended for patients with renal impairment where creatinine clearance is less than 35 ml/min, due to lack of experience.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients
  • Abnormalities of the oesophagus and other factors which delay oesophageal emptying, such as stricture or achalasia
  • Inability to stand or sit upright for at least 30 minutes
  • Hypocalcaemia
  • Not to be used in children less than 18 years of age (safety and efficacy not established)
  • Not to be used during pregnancy or breast-feeding
  • Not recommended where creatinine clearance is less than 35 ml/min

Side effects

  • Common: abdominal pain, dyspepsia, constipation, diarrhoea, flatulence, oesophageal ulcer, dysphagia, abdominal distension, acid regurgitation
  • Common: headache, dizziness; vertigo
  • Common: alopecia, pruritus
  • Common: musculoskeletal (bone, muscle or joint) pain
  • Uncommon: nausea, vomiting, gastritis, oesophagitis, oesophageal erosions, melaena
  • Uncommon: dysgeusia; eye inflammation (uveitis, scleritis or episcleritis); rash, erythema
  • Rare: oesophageal stricture, oropharyngeal ulceration, upper gastrointestinal perforation, ulcers and bleeding
  • Rare: hypersensitivity reactions including urticaria and angioedema; symptomatic hypocalcaemia, often with predisposing conditions
  • Rare: rash with photosensitivity; severe skin reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis
  • Very rare: osteonecrosis of the external auditory canal (bisphosphonate class adverse reaction)
  • Osteonecrosis of the jaw has been reported in patients with osteoporosis receiving oral bisphosphonates
  • This side-effect list may be incomplete — check the full SPC.

Monitoring

  • SPC 4.4: 'Alendronate can cause local irritation of the upper gastro-intestinal mucosa.' Use caution in active upper gastrointestinal problems (dysphagia, oesophageal disease, gastritis, duodenitis, ulcers) or a recent history within the previous year of major gastrointestinal disease such as peptic ulcer, active gastrointestinal bleeding, or upper gastrointestinal surgery other than pyloroplasty. In known Barrett's oesophagus, weigh benefits and risks individually.
  • SPC 4.4: 'Physicians should therefore be alert to any signs or symptoms signalling a possible oesophageal reaction and patients should be instructed to discontinue alendronate and seek medical attention if they develop symptoms of oesophageal irritation such as dysphagia, pain on swallowing or retrosternal pain, new or worsening heartburn.'
  • SPC 4.4: 'The risk of severe oesophageal adverse experiences appears to be greater in patients who fail to take alendronate properly and/or who continue to take alendronate after developing symptoms suggestive of oesophageal irritation. It is very important that the full dosing instructions are provided to, and understood by the patient.'
  • Osteonecrosis of the jaw: consider potency of the bisphosphonate, route of administration and cumulative dose; cancer, chemotherapy, radiotherapy, corticosteroids, angiogenesis inhibitors, smoking; and a history of dental disease, poor oral hygiene, periodontal disease, invasive dental procedures and poorly fitting dentures.
  • Correct hypocalcaemia before starting (it is a contraindication), and give supplemental calcium and vitamin D if dietary intake is inadequate.
  • Re-evaluate the need for continued treatment periodically, 'particularly after 5 or more years of use'.
  • This list may be incomplete — check the full SPC.

Clinical monograph

How it works

Like daily alendronate it binds bone mineral and inhibits osteoclast farnesyl pyrophosphate synthase, suppressing bone resorption; the larger weekly dose maintains the same antiresorptive effect.

Prescribing in practice

  • The same strict administration rules apply on the chosen weekly dosing day: take on rising with plain water and remain upright without food or other medicines until after the post-dose interval, as oesophageal injury risk is the key hazard.
  • If a weekly dose is missed it should be taken the next morning and the patient should then return to the original chosen day, not double up.
  • Ensure calcium and vitamin D sufficiency and counsel on the rare risks of osteonecrosis of the jaw and atypical femoral fracture.

Monitoring

Monitor renal function and calcium, and periodically reassess fracture risk and the case for a treatment break after extended use.

Counselling the patient

  • Take it on the same chosen day each week, first thing with plain water, then stay upright and avoid food and other tablets until after the interval.
  • If you forget, take it the next morning and then go back to your usual day.
  • Report swallowing problems, heartburn or new thigh or groin pain, and keep up good dental care.

Evidence & guidelines

Weekly dosing was shown to be therapeutically equivalent to daily alendronate on bone density and is endorsed within NICE osteoporosis guidance.

Reference: NICE NG187; RCP guidelines; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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