Bedwetting medicine

What is desmopressin?

Desmopressin is the most popular medicine used to treat bedwetting. A dose is given just before bedtime. It comes in two tablet forms:

• A tablet which is swallowed.

• A melt tablet which is put under the tongue to dissolve and go straight into the bloodstream.

The advantage of the melt form is that it is not affected by food in the stomach.

How does desmopressin work?

Desmopressin works by reducing the amount of urine produced in the body at night by the kidneys. This means that the bladder then fills with less urine during the night.

Desmopressin is usually taken at bedtime. Your child should only have sips of fluid from one hour before taking desmopressin until eight hours afterwards (see below).

How effective is desmopressin?

Desmopressin works in about 7 in 10 cases.

Most children who take desmopressin will have an improvement. This may be fewer wet nights than usual rather than being totally dry every night. It tends to work only when it is taken, so once desmopressin is stopped, the bedwetting comes back. This is why it is mostly used for short periods of time, such as for sleepovers or trips. However, it can be an option for longer-term treatment if other options have not worked or cannot be used.

Alternative medicines are sometimes used if desmopressin is not effective. These are usually prescribed by specialist doctors rather than by your GP.

What are the advantages of desmopressin?

Because of the way it works (reducing the amount of urine being made), it has an immediate effect on the first night of treatment. This can be very encouraging to the child.

If it has had no effect after a few days, it is unlikely to work at all. However, sometimes the initial dose is not high enough. A doctor may advise that the dose be increased if it does not work at first.

Also, it is possible that food can affect the absorption of desmopressin tablets into the body. Therefore, if it has not worked then try giving the dose at least an hour and a half after the child last ate anything. Also, don't give food to your child just before bedtime. Alternatively, you could try the melt (under the tongue) preparation.

What are the disadvantages of desmopressin?

It does not work in all cases. Also, in children where it has worked, when it is stopped there is a chance that bedwetting will return. A permanent cure following treatment is more likely with bedwetting alarms than with desmopressin.

When and how is desmopressin used?

Treatment with a bedwetting alarm is currently recommended to be used as a first-line option. However, desmopressin is recommended first-line for children who require a rapid response or short-term control of bedwetting (for example, for sleepovers or school trips). Desmopressin is used because it has a faster response rate than using an alarm. If it is used for short-term control, it is usually recommended to take it daily from around a week before the occasion for which it is needed. This gives time to assess how effective it is.

Desmopressin is generally used only in children aged over 7 years; however, sometimes it is used in children a year or two younger. It is not used in children under the age of 5 years. Children aged 5-7 years may be given desmopressin if they are not yet considered to be mature enough to use a bedwetting alarm. It can also be used as an alternative to an alarm. Some children have desmopressin in addition to using the alarm.

If it works, it can be continued for a while. If there has been a response after four weeks then it is usually given for a total of three months. It is then stopped for a week to assess the effect and to see if it is still needed. If there is only a partial response, the dose may be increased (and also be given one to two hours before bedtime). It should then be continued for another six months. However, if there is no response after four weeks then the treatment is usually stopped. Sometimes it is recommended to try taking it one or two hours before bedtime to see if this works.

Desmopressin can also be useful for short spells. For example, it may be especially helpful for holidays or times away from home (sleepovers, etc). It may also give encouragement to a child, who is fed up with bedwetting, to have a period of dry nights.

Are there any side-effects with desmopressin?

Side-effects are rare. Possible side-effects may include headache, feeling sick and mild tummy pain. These side-effects are not serious and go away if the treatment is stopped.

The most serious possible side-effect is due to the way the medicine works - it reduces the amount of urine that is made. Very rarely, this can lead to fluid overload (too much fluid in the body). This may lead to convulsions and serious problems. It has to be stressed that this is extremely rare and unlikely to happen. However, as a precaution, it is advised that when your child takes desmopressin:

• He or she should not drink too much in the evening. Normal amounts to ease thirst are fine, but not extra drinks for pleasure, such as cans of lemonade.

• He or she should not drink more than one regular cup of water (about 240 ml) from one hour before taking desmopressin to eight hours afterwards.

In effect, this means if your child is thirsty in the night, they should have small sips of water only.

Also, do not give desmopressin to a child who has diarrhoea or is being sick (vomiting) until the illness has cleared. Children with diarrhoea and vomiting should be given plenty of fluids.