<prompt> Which of the following drug causes postural hypotension commonly?ACE inhibitorBeta blockerAlpha blockerAngiotensin receptor blockers.  <response>: Alpha 1A receptors are present on prostatic urethra whereas alpha 1B1D are present on blood vessels. Drugs blocking both of these like prazosin, terazosin, doxazosin and alfuzosin are useful in BHP with hypeension but cause postural hypotension First dose effect as an adverse effect due to VENODILATION -hence causing pooling of blood in extremities -decreased venous return causing postaural hypotension. Selective alpha 1A blockers tamsulosin and silodosin treat symptoms of BHP without causing postural hypotension. Other drugs causing postural hypotension - ACE inhibitors- Enalapril Sodium nitroprusside. 