Desmopressin

Desmopressin (trade names: DDAVP, DesmoMelt, Stimate, Minirin) is a synthetic replacement for vasopressin, the hormone that reduces urine production. It may be taken nasally, intravenously, or as an oral or sublingual tablet. Physicians prescribe desmopressin most frequently for treatment of diabetes insipidus, bedwetting, or nocturia.

Chemistry
Desmopressin (1-desamino-8- D -arginine vasopressin) is a modified form of the normal human hormone arginine vasopressin, a peptide containing nine amino acids.

Compared to vasopressin, desmopressin's first amino acid has been deaminated, and the arginine at the eighth position is in the dextro rather than the levo form (see stereochemistry).

Mode of action
Desmopressin works by limiting the amount of water that is eliminated in the urine.

Desmopressin binds to V2 receptors in renal collecting ducts, increasing water reabsorption. It also stimulates release of von Willebrand factor from endothelial cells by acting on the V2 receptor.

Desmopressin is degraded more slowly than recombinant vasopressin, and requires less frequent administration. In addition, it has little effect on blood pressure, while vasopressin may cause arterial hypertension. Vasopressin stimulates the release of ACTH, which indirectly increases responsiveness of alpha-1 receptor in blood vessel smooth muscle, increasing vessel tone and blood pressure. Desmopressin does not stimultate ACTH release, and therefore does not directly raise blood pressure.

Nocturnal Enuresis
Doctors prescribe desmopressin frequently for treatment. It is usually in the form of desmopressin acetate, DDAVP. Patients taking DDAVP are 4.5 times more likely to sleep without disruption than with placebo. Examples of these situations are overnight camp and sleepovers.

US drug regulators banned treating bedwetting with desmopressin nasal sprays after two patients died and 59 other patients suffered seizures. The patients were using desmopressin when they developed hyponatremia, an imbalance of the body's sodium levels.

FDA regulators said that desmopressin tablets could still be considered safe for nocturnal enuresis treatment, as long as the patient was otherwise healthy. Patients must stop taking desmopressin if they become sick and have severe vomiting and diarrhea, fever, the flu, or severe cold. They should also be very cautious during hot weather or following strenuous exercise that may make them thirsty.

A healthy body needs to maintain a balance of water and salt (sodium). If sodium levels become too low (hyponatremia) – either as a result of increased water take-up or reduced salt levels – a person may have seizures and, in extreme cases, may die.

Coagulation disorders
Desmopressin can be used to promote the release of von Willebrand factor (with subsequent increase in factor VIII survival secondary to vWF complexing) in patients with coagulation disorders such as von Willebrand disease, mild hemophilia A (factor VIII deficiency), and thrombocytopenia. It can be used with uremic induced platelet dysfunction. It is not effective in the treatment of hemophilia B (factor IX deficiency), severe hemophilia A, or von Willebrand 2B.

Diabetes insipidus
Desmopressin is used in the treatment of central diabetes insipidus (DI), to replace endogenous ADH that is missing in the central nervous system type of this disorder (decreased production of ADH from the posterior pituitary). It is also used in the diagnostic workup for diabetes insipidus, in order to distinguish central from nephrogenic DI.

Side effects

 * headaches
 * facial flushing
 * nausea
 * hyponatremia
 * seizures