Diuretics and Antidiuretics 211Adverse effects include nausea, belching,
abdominal cramps, hypersensitivity
reactions etc.
DESMOPRESSIN
Desmopressin is a synthetic analogue
of vasopressin. Two chemical changes have
been made to natural hormone, namely
dissemination of cysteine and substitution
of 8-L-arginine by 8-D-arginine. These
structural changes result in a compound
with significantly increased antidiuretic
potency, very little activity on the smooth
muscles, hence the avoidance of
undesirable pressor effects. Desmopressin
proved to be a highly selective diuretic
agent with a ratio between antidiuretic and
vasopressor activity in excess of 2,000 : 1.
Desmopressin is more stable than
vasopressin and this is reflected in its
prolonged duration of action.
Desmopressin is a pure V2 receptor
agonist. When bound to V2 receptors in the
kidney, it increases the permeability of the
collecting ducts and tubules thereby
enhancing water reabsorption and
reducing the volume of urine produced
without any pressor effects.
Oral administration of 0.1-0.2 mg
desmopressin provides an antidiuretic effect
lasting for 8-12 hours. Desmopressin does not
cross blood brain barrier and maximal plasma
concentrations are reached within 2 hours.
After oral administration, t½ varies between
2.0 hours and 3.2 hours. 65% of oral
desmopressin absorbed is excreted unchanged
in the urine. It is also used as a nasal spray.
Adverse effects include headache,
nausea and stomach pain and in very rare
cases epistaxis. Treatment without
concomitant restriction of water intake may
lead to water retention with accompanying
signs and symptoms (reduced serum
sodium, weight gain and in serious cases,
convulsions).Therapeutic Uses- Nocturia in adults.
- Primary nocturnal enuresis.
- Central diabetes insipidus: Desmo-
pressin is preparation of choice.