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FAQ

The Condition

Q: Do bedwetting children sleep deeper?

A: Parents of bedwetting children are almost unanimous in stating that their children are nearly impossible to wake up. Attempts to validate this opinion have however been largely unsuccessful and sleep patterns appear to be perfectly normal in children with PNE. Despite a normal sleep pattern, however evidence has emerged that children with night-time bedwetting may have an abnormal arousal response to a full bladder.1

Q: Is there any evidence that night-time bedwetting results from nocturnal polyuria?

A: Yes – in many studies it has been shown that a considerable number of patients with night-time bedwetting suffer from a relatively high nocturnal urine output. This does not in itself explain bedwetting, but merely that the bladder capacity is exceeded so that voiding occurs during sleep.2

Q: Is a small bladder capacity a cause of bedwetting?

A: There is certainly some evidence that the bladder muscles are not properly relaxed during sleep in some individuals with primary night-time bedwetting3. This leads to a decreased bladder capacity and earlier initiation of the micturition reflex. The balance between bladder capacity and nocturnal urine production is important in determining the onset of a bedwetting event3. If nocturnal urine production in children is higher than the bladder capacity bedwetting will occur.

A study by Vande Walle4 provides evidence of the balance between urine volume and the bladder volume. He further relates the imbalance to the age of the child and suggests it is an immaturity of the mechanism for this balance which leads to bedwetting. The mechanism usually matures during the ages of 2 to 5. However in some subjects this maturation is delayed and results in nocturnal polyuria and bedwetting.

Mode of Action

Q: How long does DesmoMelt take to work?

A: Following sublingual administration of DesmoMelt the maximum plasma levels are seen approximately 0.5 - 2 hours after administration. Most patients respond immediately to DesmoMelt. The starting dose for DesmoMelt is 1 x 120mcg Melt at bedtime. If the effect at this lowest dose is insufficient then the dose may be raised to 2 x 120mcg or 1 x 240mcg Melt at bedtime.

Q: Do DesmoMelts have any direct effect on the bladder?

A: There is no known direct effect on the smooth muscle of the bladder.

Q: Do DesmoMelts affect blood pressure?

A: Desmopressin has no direct effect on blood pressure. Desmopressin is highly specific for the V2 receptor. Compared with vasopressin it has a pressor activity of less than 0.001%.

Q: For how long will desmopressin DesmoMelt remain in the body?

A: With a half life-time of approximately 2-3 hours, the expected pharmacological duration of action is approximately 8 hours.

Q: What is the optimal treatment duration with DesmoMelt to achieve complete dryness?

A: It is not possible to recommend an optimal duration of treatment since some patients may become dry after the first 3 months of treatment, whereas others will require longer therapy. A patient can be treated for as long as the symptoms persist. The need for continued treatment should be assessed every 3 months by withholding treatment for at least a week. If the patient wets during that time then DesmoMelt treatment can recommence at the last successful dose.

Q: Can DesmoMelt be taken with meals?

A: The absorption of desmopressin from the gastrointestinal tract has been shown to be reduced and delayed if the drug is administered together with food.

Q: Can fluid retention occur during DesmoMelt treatment without excessive fluid intake?

A: Desmopressin does not create water. Water ingestion is the primary pathogenic mechanism in water intoxication, i.e. regardless of the presence of desmopressin, fluid intake must exceed loss of water for an increase of body water to occur. It is important to stress that patients on DesmoMelt treatment must limit their fluid intake from one hour before until at least 8 hours after taking a dose. It is important to assess drinking habits prior to initiating treatment with DesmoMelt to exclude polydipsia or other conditions causing fluid or electrolyte imbalance. DesmoMelt should also be discontinued during an episode of vomiting and / or diarrhoea until fluid balance is once again normal.

Dosage

Q: What is the dosage of DesmoMelt in PNE?

A: The dosage is 1 x 120mcg DesmoMelt increasing to 2 x 120mcg or 1 x 240mcg DesmoMelt only if needed.

Q: At what age can you start using DesmoMelt for night-time bedwetting?

A: DesmoMelt is licensed for treatment of night-time bedwetting (primary nocturnal enuresis, or PNE) in patients aged 5 to 65 years.

Q: For how long can DesmoMelt be used?

A: Clinical studies indicate that desmopressin can be used long-term. A patient can be treated for as long as the symptoms persist. The need for continued treatment should be assessed every 3 months by witholding treatment for at least a week. If the patient wets during that time then DesmoMelt treatment can recommence at the last successful dose.

Q: Are there any negative effects after long term treatment with desmopressin?

A: Based on the results in our post-marketing safety database and long-term studies, there appear to be no specific long term side effects.

Q: Is there any difference between doses for adults and children?

A: There does not seem to be evidence of increased dosage needs in adults compared to children. At any age group patients doses appear to be individual.

Q: What is the maximum dose?

A: The maximum recommended dosage of DesmoMelt for night-time bedwetting is 240mcg at bedtime.

Q: What happens if a patient overdoses?

A: An overdose of DesmoMelt leads to a prolonged duration of action with an increased risk of water retention and/or hyponatraemia. Although the treatment of hyponatraemia should be individualised, the following general recommendations can be given: hyponatraemia is treated by discontinuing the desmopressin treatment, fluid restriction and symptomatic treatment if needed.

Precautions

Q: Which drugs should not be taken in combination with DesmoMelt?

A: Substances which are known to induce SIADH eg, tricyclic antidepressants, selective serotonin re-uptake inhibitors, chlorpromazine and carbamazepine, may cause an additive antidiuretic effect leading to an increased risk of water retention and/or hyponatraemia. NSAIDs may induce water retention and/or hyponatraemia. Concomitant treatment with loperamide may result in a 3-fold increase of desmopressin plasma concentrations, which may lead to an increased risk of water retention and/or hyponatraemia. Although not investigated, other drugs slowing transport might have the same effect. If you have any queries or specific interactions please contact the Medical Information department: medical@ferring.com.

Q: Can you give DesmoMelt together with anticholinergics such as oxybutynin?

A: Formal interaction studies have not been performed on this combination so far. However, good clinical results are reported in patients characterised as not responding to desmopressin as mono therapy.

Q: Can DesmoMelt be used in patients with asthma and PNE?

A: There are no specific reasons why a patient with asthma cannot be treated with DesmoMelt for PNE provided they fulfil all the other conditions outlined in the Summary of Product Characteristics

Side Effects

Q: Are there any side effects?

A: Side-effects include headache, stomach pain and nausea. Isolated cases of allergic skin reactions and more severe general allergic reactions have been reported. Very rare cases of emotional disturbances in children have been reported. Treatment with desmopressin without concomitant reduction of fluid intake may lead to water retention/hyponatraemia with accompanying symptoms of headache, nausea, vomiting, weight gain, decreased serum sodium and in serious cases, convulsions. If a patient reports any suspected side effects with desmopressin please contact the Medical Information Department at medical@ferring.com. Information about adverse event reporting can be found at www.yellowcard.gov.uk. Adverse events should also be reported to Ferring Pharmaceuticals Ltd.: Medical Information, Ferring Pharmaceuticals Ltd., Drayton Hall, Church Road, West Drayton, UB7 7PS, United Kingdom. Email: medical@ferring.com.

Q: Does Desmopressin affect endogenous hormone?

A: Desmopressin has not been shown to impair the body's ability to produce vasopressin or affect circulating levels of other hormones.

Q: Does Desmopressin have any effect on electrolytes?

A: Desmopressin exerts its main effect in the distal tubule in the kidney where it reabsorbs water. Excessive water re-absorption might result in drops in serum electrolyte concentrations by dilution.

Q: If a patient complains of a headache, should the medication be stopped?

A: A recent review showed 2% of patients report headaches while on desmopressin 4. They tend to be mild and self limiting in nature. However if a patient complains of a severe or prolonged headache this can be one of the signs of hyponatraemia. Treatment should be stopped, fluid restricted and the patient should speak with their Doctor or should visit their hospital for further assistance. A mention of this is made on the Patient Information Leaflet for DesmoMelt.

General

Q: What is the recommended fluid intake over a day?

A: We do not give a recommended fluid intake over 24 hours as each person had his or her own "normal" intake. What we would recommend is sensible drinking during the day. The patient should restrict fluid from 1 hour before taking the Melt at bedtime until the next morning and in any case for a minimum of 8 hours after a dose of DesmoMelt. Desmopressin should not be used to treat bedwetting in patients with an unusually high fluid intake. It is important to assess drinking habits prior to initiating treatment with DesmoMelt to exclude polydipsia or other conditions causing fluid or electrolyte imbalance.

Butler 2000
Rittig 1989
Norgaard 1985
Vande Walle 1998
van Kerrebroeck2002