This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
When treating hypeension chronically, ohostatic hypotension is maximum with: 
Select and explain. 
A. Clonidine, B. Guanethidine, C. Prazosin, D. Propanolol
B: Guanethidine
Answer: B: Guanethidine 
Explanation: Postural hypotension cause by a-blockers is called first dose hypotension because tolerance occurs to this adverse effect on chronic use. On the other hand, adrenergic neuron blockers continue to produce ohostatic hypeension even on chronic use.