Alendronic acid: osteoporosis tablet and how to take it safely

Alendronic acid is a bisphosphonate used to treat osteoporosis and to prevent bones from deteriorating in people at risk, for example after the menopause, with a low body mass index, heavy alcohol or tobacco use, long-term steroid treatment or certain cancer treatments.

It works by slowing down how quickly bone is broken down, helping to maintain bone strength. Brand names listed by the NHS are Fosamax and Binosto, along with Fosavance and Bentexo, which contain vitamin D3. It is prescription-only and comes as tablets, water-soluble tablets and a liquid.

The usual dose is 70 mg once a week, or a 10 mg tablet every day, and your prescriber will confirm which. Take it at the same time each day or on the same day each week, on an empty stomach, usually 30 minutes before breakfast and before any other food, drink or medicine.

Use only plain tap water. Mineral water, tea, coffee, juice and milk reduce how much is absorbed. You must stay sitting up or standing for 30 minutes after taking it, and it must never be taken at bedtime, because the tablet can irritate the food pipe if it lingers.

• Missed a daily dose? Skip it and resume the next morning. Missed a weekly dose? Take it the morning after you remember, and never double up on the same day.

• If you take too much, drink a full glass of milk, do not make yourself sick, stay upright for 30 minutes and contact NHS 111.

• Leave at least 30 minutes between alendronic acid and other oral medicines.

Most adults can take it, and children with osteoporosis only if a specialist prescribes it. Tell your doctor or pharmacist if you have had an allergic reaction to it, problems with digestion or swallowing that affect the food pipe, previous dizziness from it, an inability to stay upright for 30 minutes, low blood calcium, kidney problems, active cancer or chemotherapy or radiotherapy, dental problems or planned dental work, or a smoking history, which raises the dental risk. Pregnancy, planning pregnancy and breastfeeding should be mentioned too.

More common effects are indigestion, bloating and wind, constipation, diarrhoea, dizziness, headaches, muscle and joint pain, swollen joints or limbs, tiredness and hair loss. Staying upright for at least 30 minutes and eating smaller meals slowly help with indigestion.

Contact a doctor or call NHS 111 for heartburn or difficulty swallowing, which can signal ulcers in the food pipe, flu-like symptoms with fever, loose teeth or mouth sores or swelling (and tell your dentist), pain in the thigh, hip or groin, severe joint, muscle or bone pain, black or red stools, blurred or painful red eyes, or muscle cramps with tingling that may point to low calcium. Call 999 for a serious allergic reaction.

Suspected side effects can be reported through the Yellow Card scheme.

Treatment usually lasts at least 3 to 5 years. In rare cases, use beyond 2 years may increase the risk of inner-ear bone damage or certain thigh-bone fractures. After 3 to 5 years your doctor may suggest a break or stopping, as the benefit continues for 2 to 3 years after treatment ends, and a bone density scan is usually done to reassess.

The NHS advises keeping your teeth clean, having a dental check-up every 6 months, reporting any mouth or teeth problems at once and telling your dentist before dental procedures because of the small jawbone risk.

Alendronic acid is not recommended in pregnancy because of insufficient safety research. It is usually fine to take while breastfeeding after talking to a professional. There is no evidence it reduces fertility, but people planning pregnancy should talk to their doctor, as they typically need to stop it before conception.

Antacids and magnesium-containing laxatives should not be taken at the same time. The NHS also lists the cancer medicines bevacizumab and thalidomide, steroids such as prednisolone and dexamethasone (which may raise jawbone risk), ibuprofen (more stomach irritation; low-dose aspirin is fine), the antibiotics gentamicin, amikacin and tobramycin, deferasirox and chemotherapy. Calcium, iron, magnesium and zinc supplements need to be mentioned.

You can drink alcohol, but too much weakens bones and raises fracture risk, so stay under 14 units a week. Alendronic acid can cause dizziness and blurred vision; if so, do not drive. Eat calcium-rich foods such as milk, cheese and broccoli, but wait 30 minutes after the tablet before eating or drinking anything other than tap water.