How does it work?

Didronel tablets contain the active ingredient etidronatedisodium, which is a type of medicine known as a bisphosphonate. Bisphosphonates are medicines thatreduce the turnover of bone.

Bone is not a static structure. It is continually shaped,reformed and rebuilt by cells called osteoblasts and osteoclasts. These cellscontinously deposit and remove calcium and phophorous, stored in a proteinnetwork that makes up the structure of the bone. Old bone is broken down by theosteoclasts and new bone is formed by the osteoblasts.

In Paget's disease of bone the normal metabolism of bone isdisturbed. There is an increase in bone breakdown by the osteoclasts andincreased and irregular formation of new bone by the osteoblasts. The normalbone marrow also becomes replaced with blood vessels and fibrous tissue. Inthis disease there are often no symptoms for many years, but over time thebones can become enlarged, deformed, painful, weak and prone to breaking. Theenlarged and deformed bones can also put pressure on nerves, causing pain andmuscle weakness.

Etidronate disodium works by binding very tightly to the boneand preventing the calcium being removed by the osteoclasts. This stops theosteoclasts from breaking down the bone. It also reduces the rate of boneformation by the osteoblasts. The reduced bone turnover helps to reducedeformity and keep the bones strong and less likely to break.

What is it used for?

• Bone disease called Paget's disease, in which there is excessive breakdown of bone and increased and irregular formation of bone, causing the bones to become enlarged, deformed, painful, weak and prone to breaking.

How do I take it?

• Didronel tablets are taken once a day. The dose prescribed depends on your body weight. Follow the instructions given by your doctor. These will be printed on the dispensing label that your pharmacist has put on the packet of medicine.
• Didronel tablets should be swallowed with water on an empty stomach. You should not eat or drink anything other than water in the two hours before and the two hours after taking the tablets. This is because food and some drinks (particularly milk and dairy products) can interfere with the absorption of the medicine from the gut and hence make it less effective.
• You should not take antacids or mineral supplements in the two hours before or after taking your Didronel tablets, as these can also interfere with the absorption of the medicine from the gut. See the end of this page for more information.

Warning!

• Your doctor may want to monitor various components of your blood and urine while you are taking this medicine, to make sure it is working properly.
• If you have kidney problems or have ever had a kidney stone, the amount of calcium in your blood and urine should be regularly monitored while you are taking this medicine.
• People with Paget's disease are more likely to break bones. If you fracture a bone while taking this medicine, treatment should be stopped and not restarted until the bone is completely healed. This is because the medicine can slow down the mineralisation of newly formed bone tissue, so may make the healed bone tissue weak.
• Your course of treatment will be a maximum of either three or six months, depending on the dose your doctor has prescribed you. If your doctor decides re-treatment is necessary after this time because the disease has flared up again, etidronate should only be re-started after you have had an interval of at least three months without taking it.
• The class of medicines that etidronate disodium belongs to (bisphosphonates) has been associated with a rare condition called osteonecrosis of the jaw. The majority of cases of this condition have been in cancer patients treated with bisphosphonates by injection into a vein, and many of these people were also having treatment with chemotherapy or corticosteroids. However, the condition has also been seen in people taking bisphosphonates by mouth. The risk may also be increased by poor oral hygiene, dental problems such as gum disease or poorly fitting dentures, teeth extractions, oral surgery and smoking. For this reason, you should have a dental examination and, if necessary, appropriate preventive dentistry, before you start treatment with this medicine. Discuss this with your doctor. It is important to look after your mouth and teeth as much as possible while you are taking this medicine. You should have regular check-ups with your dentist and get advice straight away if you have any problems with your mouth or teeth. When you see a dentist during treatment, make sure they know you are taking this medicine. Invasive dental procedures such as tooth extraction or surgery should be avoided if possible.
• Some people being treated with bisphosphonates (mainly people having long-term treatment for osteoporosis) have experienced an unusual fracture of their thigh bone. For this reason it is important to let your doctor know if you get any pain in your thighs, hips or groin while you are having treatment with this medicine. These symptoms could be an early indication of a possible fracture.

Use with caution in

• Decreased kidney function.
• History of kidney stones.
• People with chronic (long-term) diarrhoea.

Not to be used in

• People with softening of the bones due to a deficiency in vitamin D or calcium (osteomalacia).
• Severely decreased kidney function.
• Pregnancy.
• Breastfeeding.
• This medicine is not recommended for children.

This medicine should not be used if you are allergic to one orany of its ingredients. Please inform your doctor or pharmacist if you havepreviously experienced such anallergy. If you feel you haveexperienced an allergic reaction, stop using this medicine and inform yourdoctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy orbreastfeeding. However, other medicines may be safely used in pregnancy orbreastfeeding providing the benefits to the mother outweigh the risks to theunborn baby. Always inform your doctor if you are pregnant or planning apregnancy, before using any medicine.

• The safety of this medicine in pregnancy has not been established. It should not be taken by women who are pregnant, and women who could get pregnant should use an effective method of contraception to prevent pregnancy while taking this medicine. Seek further medical advice from your doctor.
• It is not known if this medicine passes into breast milk. It should not be used by women who are breastfeeding. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individualpeople in different ways. The following are some of the side effects that areknown to be associated with this medicine. Just because a side effect is statedhere, it does not mean that all people using this medicine will experience thator any side effect.

• Diarrhoea.
• Feeling sick.
• Pins and needles sensations.
• Confusion.
• Increased bone pain (tell your doctor if you get this).
• Pain in the joints (arthralgia or arthritis).
• Severe swelling of lips, face or tongue (angioedema).
• Rash or itching.
• Worsening of asthma.
• Worsening of peptic ulcer.
• Decreased levels of white blood cells or platelets in the blood.
• Burning of the tongue.
• Hair loss.
• Osteonecrosis of the jaw (see warning section above).
• Unusual fracture of the thigh (see warning section above).

The side effects listed above may not include all of the sideeffects reported by the medicine'smanufacturer. For moreinformation about any other possible risks associated with this medicine,please read the information provided with the medicine or consult your doctoror pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicinesyou are already taking, including those bought without a prescription andherbal medicines, before you start treatment with this medicine. Similarly,check with your doctor or pharmacist before taking any new medicines whiletaking this one, to make sure that thecombination is safe.

The following medicines should not be taken in the two hoursbefore or the two hours after taking your Didronel tablets, as they may reduce theabsorption of the medicine from the gut and make it less effective:

• antacids (indigestion remedies)
• calcium supplements
• iron supplements
• laxatives containing magnesium
• mineral supplements
• multivitamins containing minerals such as calcium, iron, magnesium or zinc
• zinc supplements.

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that contain just etidronate disodium as the active ingredient.

Didronel PMO contains etidronate in combination with calcium carbonate.