BMA Concise Guide to Medicine & Drugs


Brand name Didronel

Used in the following combined preparation Didronel PMO


Drug group Drug for bone disorders

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic No


Etidronate is given for the treatment of bone disorders such as Paget’s disease. It acts only on the bones, reducing the activity of bone cells that break down bone tissue and thereby stopping the progress of the disease. This action also stops calcium from being released from the bones into the bloodstream, so it reduces the amount of calcium in the blood. Etidronate is also used together with calcium tablets to treat osteoporosis in postmenopausal women and to prevent and treat steroid-induced osteoporosis. Generally, the drug’s side effects are mild. The most common is diarrhoea, which is more likely with higher doses. If taken at high doses (20mg/kg body weight daily), the drug inhibits bone formation, which can lead to thinning of the bones and fractures. For this reason, high doses must be carefully monitored and used for as short a time as possible. The effect is reversed on stopping the drug.


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 on an empty stomach, 2 hours before or after food or dietary supplements.

Dosage range Paget’s disease 5–20mg/kg body weight daily for a maximum of 3–6 months. Courses may be repeated after a break of at least 3 months. Osteoporosis 400mg daily for 2 weeks, repeated every 3 months.

Onset of effect Within 1 month.

Duration of action Some effects may persist for several weeks or months.

Diet advice Absorption of etidronate is reduced by foods, especially those containing calcium (e.g. dairy products), so the drug should be taken on an empty stomach. Iron and antacids also reduce absorption. The diet must contain adequate calcium and vitamin D; supplements may be given.

Storage Keep in original container below 30°C out of the reach of children. Protect from light.

Missed dose Take as soon as you remember. If your next dose is due within 6 hours, take a single dose now and skip the next.

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 numbness and muscle spasm. Notify your doctor.


The most common side effect, diarrhoea, is more likely to occur if the dose of etidronate is increased above 5mg/kg daily. Other common side effects include nausea, constipation, and abdominal pain. If any of these side effects are severe, or if you experience rash, itching, facial swelling, severe headaches, or jaw pain, discuss with your doctor. In some patients with Paget’s disease, bone pain may be increased initially but usually disappears with further treatment. However, if you experience bone pain, bruising, fever, or a sore throat, you should notify your doctor without delay.


Antacids and products containing calcium, magnesium, or iron These products should be given at least 2 hours before or after etidronate to minimize the risk of reduced absorption of etidronate.


Be sure to tell your doctor if:

· You have kidney problems.

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

· You have low calcium levels in your blood.

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

· You have colitis.

· 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 No special problems.


In patients with Paget’s disease, courses of treatment longer than 3 to 6 months are not usually prescribed, but repeat courses may be required. When used to treat or prevent osteoporosis, however, etidronate may be taken long-term, in cycles.

Monitoring Your doctor may monitor your bone mineral density. Blood and urine tests may be carried out at intervals.