Family doctor

USE: Bedwetting (nocturnal enuresis), central diabetes insipidus (not sugar diabetes), testing kidney function (the capacity to concentrate urine), some blood disorders.

Desmopressin works like vasopressin (a natural hormone in the body) to allow the body to reabsorb water from the kidneys which increases the concentration of the urine and reduces the quantity of urine. Therefore, the need to use the toilet (urinate) is reduced. Desmopressin can be used for a short time in bedwetting in children over 5 years of age. It is also used in cases where the body is not reabsorbing enough liquid from the kidneys.

The usual dose for children for bedwetting is 10 to 40 mcg (one to four puffs of the spray) into the nose at night, and it lasts for 8 hours or more. If using 10 mcg this is just one puff into one nostril only (for this nose spray you do not have to use the same dose in both nostrils). This dose may be varied by the doctor to give best effect.

For central diabetes insipidus the usual dose is 20 to 40 mcg (two to four puffs of the spray) and children 10 to 20 mcg (one to two puffs of the spray) either given in a single dose or divided into two or three doses - according to the needs of the individual.

Minirin comes in nose spray, nose drops and tablets. In New Zealand the tablets aren't "free" on prescription and require many times more medicine for the same effect as the nose spray or drops because much of the medicine is destroyed in the stomach and intestines. Octostim also contains desmopressin but is much stronger for control of bleeding under a doctor's supervision, and must not be used in place of Minirin.

Cautions:

Do not use if:

• Excessive quantities of water are being taken all the time
• Diuretics are being taken
• You are allergic to the ingredients (chlorobutanol is the preservative in the formulation available in New Zealand)

If any of the following factors are present the doctor may not want to use this medicine, or may want to take special care:

• Young or elderly patients
• Imbalance of fluid and/or electrolytes (e.g. dehydration, or potassium or sodium not the right concentration in the body)
• Use of diuretics (fluid pills)
• If there is a risk of increased intracranial pressure
• If there are nose problems which might affect the medicine going into the blood stream, e.g. scarring inside the nose.

Side effects:

When used into the nose possible side effects include local irritation, congestion and nosebleed.

As this medicine causes increased water to be reabsorbed from the kidneys, use with other medicines which also have this same effect can increase the risk of water intoxication (too much water in the body) or low sodium in the bloodstream, e.g. tricyclic antidepressants, carbamazepine, chlorpromazine, fludrocortisone. The risk of water intoxication or low sodium can be reduced by avoiding these medicines, avoiding drinking too much (just enough to satisfy thirst) for 1 hour before and 8 hours after using, and using only the recommended dose.

Other possible side effects include headache, stomach pain and nausea.

Interactions:

As this medicine causes increased water to be reabsorbed from the kidneys, use with other medicines which also have this same effect can increase the risk of water intoxication (too much water in the body) or low sodium in the bloodstream, e.g. tricyclic antidepressants, carbamazepine, chlorpromazine, and fludrocortisone.

Patient information:

• Follow the instructions on the label of the medicine or as directed by your doctor.
• Store the nose spray and nose drops in the fridge.
• Do not give this medicine to anyone else. If two people in the family are prescribed it, make sure they use only their own nasal spray - it is not a good idea to swap nose sprays.
• If taking for bedwetting drink a minimum of fluid (just enough to satisfy thirst) from 1 hour before to 8 hours after using the nose spray or drops.
• Usually there will be a one week period without using desmopressin after three months to decide whether the medicine is still required (bedwetting only).
• If vomiting or diarrhoea occur check with your doctor or pharmacist whether you should use this medicine while sick (you may need to stop it temporarily).