Minirin 0.1mg (Desmopressin)

Minirin general information

What is Minirin used for?

Minirin tablets 0.1mg are used to treat several conditions characterised by over production of urine or uncontrolled release of urine.  Normally the amount of urine produced in the kidneys is controlled by vasopressin (arginine vasopressin or AVP), also known as antidiuretic hormone (ADH), a hormone produced in the hypothalamus of the brain, stored in the pituitary gland and released in response to dehydration, such as through perspiration or insufficient water intake.  AVP acts directly on the kidney tubules to cause reabsorption of water as the urine passes through. 

Central diabetes insipidus (DI) is a condition in which the body does not make enough AVP resulting in extreme thirst (polydipsia) and excessive urination (polyuria).  DI is not related to Diabetes Mellitus (DM) and is usually caused by damage to the pituitary gland or hypothalamus region of the brain due to brain trauma, surgery or infection such as meningitis.  Nocturnal enuresis, or bedwetting at night, is a common form of incontinence in children.  Primary nocturnal enuresis is involuntary urination while asleep, in children that have not achieved continence beyond the age at which bladder control should been learnt.  This may be due to several factors including more urine production than the child’s bladder has capacity for, excessive urine production, which may be due to insufficient secretion of AVP or inability to awaken from sleep in response to a full bladder.  Nocturia in adults is associated with over production of urine at night exceeding bladder capacity and requiring emptying of the bladder, which becomes more common as we age.  Although it should be possible to sleep up to 6 to 8 hours without the need to urinate, those with nocturia waken often, with a full bladder which can cause disrupted sleep patterns.  The need to urinate may be associated with already poor sleep patterns, or with the production of large volumes of urine at night (nocturnal polyuria) due to several conditions including DI and lack of the usual increase in AVP secretion at night.

Minirin tablets 0.1mg work through a common mechanism to treat central DI to help control dehydration and increased thirst, primary nocturnal enuresis to control bedwetting in children over 5 years, and nocturia in adults, to reduce urine production and control the need to urinate at night.

How does Minirin work?

Minirin tablets 0.1mg contain desmopressin, a synthetic structural analogue of arginine vasopressin (AVP) that is used to reduce urine production in conditions where there is over production of urine due to a lack of the endogenous (naturally produced) antidiuretic hormone.  Desmopressin has increased potency and stability compared to AVP, but does not have the pressor effects of AVP, which means that it does not increase blood pressure.  AVP acts directly on the tubules of the kidney at the distal portion of the nephron, which is the functional unit of the kidney, at the collecting duct where the water and salt concentration of the urine is regulated.  Binding of AVP to specific cell surface receptors (AV2) in the nephron, triggers a membrane bound enzyme, adenylate cyclase to produce cAMP (cyclic adenosine monophosphate), which activates an intracellular signal transduction mechanism to open water channels (aquaporins) through which water is reabsorbed from the urine back into the blood.  Desmopressin in Minirin tablets 0.1mg binds potently and selectively to the AV2 receptors to promote water absorption from the urine back into the blood, which reduces urine volume and is effective for between 6 and 14 hours.  Minirin tablets 0.1mg are effective in treating symptoms associated with over production of urine (polyuria) in DI, primary nocturnal enuresis and nocturia.

What does Minirin contain?

Minirin tablets 0.1mg contain the active ingredient desmopressin acetate that is used to reduce the production of urine in conditions due to insufficient AVP.  They also contain lactose monohydrate, potato starch, povidone and magnesium stearate.

Treating polyuria with Minirin

Minirin tablets 0.1mg contain desmopressin, a synthetic analogue of arginine vasopressin (AVP), which is the natural (endogenous) antidiuretic hormone (ADH) that is used to treat conditions characterised by polyuria (production of large amounts of urine and/or excessive urination) to reduce urine production.  AVP is a hormone produced in the hypothalamus of the brain, stored in the pituitary gland and released in response to dehydration, such as through perspiration or insufficient water intake.  This balance sometimes breaks down in conditions where more urine is produced that the bladder has capacity for.  These include central diabetes insipidus (DI), a condition in which the body does not make enough AVP resulting in extreme thirst (polydipsia) and excessive urination (polyuria).  Primary nocturnal enuresis or bedwetting in children that have not achieved continence beyond the age at which bladder control should been learnt.  Nocturia in adults associated with over production of urine at night exceeding bladder capacity and requiring emptying of the bladder, which becomes more common with age.  Insufficient AVP release is a key factor in each of these conditions, as well as insufficient bladder capacity and/or control. 

Desmopressin in Minirin tablets 0.1mg is a highly potent and stable analogue of AVP, with strong antidiuretic activity but it does not have the pressor effects of AVP, which means that it does not increase blood pressure.  It acts directly on the tubules of the kidney at the distal portion of the nephron, which is the functional unit of the kidney, where the water and salt concentration of the urine is regulated.  Binding of AVP to specific cell surface receptors (AV2) in the nephron, triggers an intracellular signal transduction cascade that opens water channels through which water is reabsorbed from the urine back into the blood.  Desmopressin in Minirin tablets 0.1mg binds potently and selectively to the AV2 receptors to promote water reabsorption which reduces urine volume.  Desmopressin in Minirin tablets 0.1mg helps control dehydration and increased thirst in DI, bedwetting in children with primary nocturnal enuresis, urine and production and the need to urinate at night in adults with nocturia.

What are the side effects of Minirin?

The most commonly reported side effects when taking Minirin tablets 0.1mg include hyponatraemia (low blood sodium), which may cause headache, abdominal pain, nausea, vomiting, diarrhoea, constipation weight increase, dizziness, confusion, malaise; also oedema, fatigue.

When should Minirin not be used?

You should not use Minirin tablets 0.1mg if you:

• are allergic to desmopressin, AVP or any ingredients in Minirin
• are pregnant or are breastfeeding, without discussion with your doctor
• have kidney disease
• drink large amounts of fluid
• known hyponatraemia (low blood sodium)
• have syndrome of inappropriate ADH secretion (SIADH) which causes excessive release of ADH
• cardiac insufficiency (heart failure) or other conditions requiring treatment with diuretics
• are taking medicines that interact with Minirin including tricyclic and SSRI antidepressants, anticonvulsants like carbamazepine, antipsychotics like chlorpromazine, sulfonylurea antidiabetic medications like chlorpropamide, NSAIDs for pain and inflammation, loperamide for diarrhoea,

What medications interact with Minirin?

Several medications interact with Minirin tablets 0.1mg and should either not be taken while you are taking Minirin or only after discussion and instruction from your doctor:

• Drugs that cause a serious reaction with Minirin: tricyclic and SSRI antidepressants; anticonvulsants like carbamazepine, antipsychotics like chlorpromazine, sulfonylurea antidiabetic medications like chlorpropamide, can induce release of ADH (SIADH); NSAIDs for pain and inflammation, loperamide for diarrhoea can increase risk of water retention and hyponatremia
• Drugs that affect Minirin: loperamide for diarrhoea

How should Minirin be taken?

You should take your Minirin tablets 0.1mg swallowed whole with a glass of water without food, as a meal can reduce the antidiuretic effect and its duration.  The dose you take and how often depends on what you are being treated for and your doctor’s recommendation.  For DI this is usually 3 times daily.  For nocturia and primary nocturnal enuresis you should take your Minirin tablets 0.1mg at bedtime.  While taking your Minirin tablets 0.1mg you should restrict your fluid intake and only drink enough to prevent thirst.  You should continue to take your Minirin tablets 0.1mg for as long as recommended by your doctor.

How long should you take Minirin?

You should continue to take your Minirin tablets 0.1mg for as long as recommended by your doctor.

Missed dose of Minirin

If you miss a dose of Minirin tablets 0.1mg take it as soon as you remember, unless it is time to take the next dose, then skip the missed dose.  Do not take a double dose.

How should Minirin be stored?

You should store your Minirin tablets 0.1mg below 25°C in a cool dry place.