Basis:
Vasopressin anti diuretic hormone of the posterior pituitary gland.
It has a potent vasoconstriction + antidiuretic activity.
It isused for upper esophageal bleeding (20units/ 15 mints).
And also used for diabetes insipidus (5-20units/4hrs)
Desmopressin
An analogue of vasopressin
Has anti diuretic activity
Has no vasoconstrictor activity
Used as nasal spray
For maintenance therapy in diabetes insipidus
Type of Assay:
2x2 randomized graded response assay.
Reference Standard:
Similar to oxytocin,
Freeze / acetone dried powder in ampoule containing 0.05mg of standard preparation = 1 unit.
1 ampoule contains 8.2 units
Methods of Bioassay:
Official:
Rat blood pressure method
Antidiuretic activity in ethanol rats
Unofficial:
RIA
Method Using Blood Pressure Of Anesthetized Rats:
Rats weighing 300gm are anesthetized with 1.75ml/kg of 25% urethane (I.P).
It is treated with ganglion blocker like hexamethonium (1mg) to produce a steady base line.
External jugular vein cannulated for injection of drug.
Internal carotid artery cannulated for recording blood pressure.
Doses of references standard + test drug injected in a randomized 2x2 assay.
Volume of injection 0.1-0.5ml.
Initial dose of reference standard may be tried in the range of 6-10 micro units.
Relative potency is calculated.
This method can also be used for the assay of Epinephrine & Norepinephrine.
Method Using Anti Diuretic Activity Highly Anesthetized Rats:
Rat weighing 250-300 grams are hydrated and anesthetized with oral dose of 5ml/100g of 2.5% ethanol.
Urinary bladder cannulated for the collection of urine.
Tail vein is cannulated for injection of drugs.
Urine output is replaced by oral administration of 0.5% ethanol.
Decrease in urine output is taken as a parameter anti diuretic activity.
The
of standard & test drug are injected for a 2x2 assay & relative potency is calculated.
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