BMA Concise Guide to Medicine & Drugs

Alendronic Acid

Brand names Fosamax, Fosamax Once Weekly

Used in the following combined preparation Fosavance


Drug group Drug for bone disorders

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Alendronic acid is used to treat osteoporosis. It is also used in the treatment and prevention of corticosteroid-induced osteoporosis and to prevent postmenopausal osteoporosis in women at risk of developing the disease. A calcium supplement and vitamin D may be prescribed with the drug if dietary amounts are not adequate, but calcium should not be taken at the same time as alendronic acid because calcium is one of many substances that reduce its absorption. Combined use of alendronic acid with HRT in postmenopausal women is more effective than either treatment alone. Alendronic acid tablets should be taken on getting up in the morning, swallowed whole with a full glass of tap water (not even mineral water is acceptable because of the minerals’ possible effect on absorption). After taking the tablet(s), remain upright for at least 30 minutes. This is to prevent the drug from sticking in the oesophagus, where it could cause ulcers or irritation.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets.

Frequency and timing of doses Once daily, first thing in the morning. Once weekly, first thing in the morning (post-menopausal women). Take with water.

Adult dosage range Treatment: men: 10mg daily; postmenopausal women: 10mg daily or 70mg weekly. Prevention: 5mg (postmenopausal women). Prevention and treatment of corticosteroid-induced osteoporosis: 5mg; postmenopausal women not taking HRT, 10mg.

Onset of effect It may take months to notice an improvement.

Duration of action Some effects may persist for months or years.

Diet advice Do not eat or take other medicines for at least 30 minutes after doses.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take the next dose at the usual time next morning.

Stopping the drug Do not stop the drug without consulting your doctor. Stopping the drug may lead to worsening of the underlying condition.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause stomach problems including heartburn, irritation, and ulcers. Notify your doctor at once, and try to remain upright.


The most frequent adverse effect of alendronic acid is abdominal pain and distension. Discuss with your doctor if abdominal pain is severe. Other adverse effects include diarrhoea or constipation; muscle, joint, or bone pain; headache; and nausea or vomiting. Discuss with your doctor if any of these are severe. If the drug causes a rash, abnormal sensitivity to light, eye inflammation, or jaw pain, consult your doctor. Rarely it can cause severe irritation and inflammation of the oesophagus that may lead to pain or difficulty in swallowing, or new or worsening heartburn. If any of these occur, stop taking the drug and consult your doctor.


Antacids and products containing calcium or iron These reduce the absorbtion of alendronic acid and should be taken at a different time of day.


Be sure to tell your doctor if:

· You have pain or difficulty in swallowing, or problems with your oesophagus.

· You have a history of peptic ulcers or stomach problems.

· You have long-term kidney problems.

· You have low calcium levels in your blood.

· You are/may be pregnant or are planning pregnancy.

· You are unable to sit or stand upright for at least 30 minutes.

· You are taking other medicines.

Pregnancy Not recommended.

Breast-feeding Not recommended.

Infants and children Not recommended.

Over 60 No special problems.

Driving and hazardous work No special problems.

Alcohol Avoid. May cause further stomach irritation.


Alendronic acid is usually prescribed indefinitely for osteoporosis without causing any problems.

Monitoring Blood and urine tests may be carried out at intervals.