Paper I — 2019 July (Supplementary) (2010 Scheme) — Q2
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Paper I
2019 July (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Read the clinical problem and answer the following question:
An elderly male aged 70 years was brought to the outpatient department with
complaints of difficulty in passing urine, poor stream & post void dribbling. Examination
revealed that he had benign prostatic hypertrophy (BPH) and his BP was 160/ 100 mm
of Hg. (2+2+2).
What drug will you prescribe to take care of both BPH & hypertension
Explain the mechanism of action of the drug in this patient
What do you understand by ‘first dose effect’ of Prazosin
Q26 marksEssays
Answer
(a) Drug for both BPH and hypertension
Prazosin (or another selective α1-blocker, e.g., Terazosin) — appropriate since a single drug can address both conditions in this elderly patient
(b) Mechanism of action in this patient
Prazosin is a selective α1-adrenergic receptor antagonist
In BPH: blocks α1 receptors in the smooth muscle of the prostate capsule, prostatic urethra, and bladder neck, relaxing this smooth muscle and reducing urethral resistance, thereby improving urine flow and relieving obstructive symptoms
In hypertension: blocks α1 receptors in vascular smooth muscle, causing arteriolar and venous vasodilatation, reducing peripheral vascular resistance and blood pressure
(c) “First-dose effect” of prazosin
Refers to the marked, sudden postural (orthostatic) hypotension, dizziness, and syncope that can occur after the very first dose (or a dose increase) of prazosin, due to profound venodilatation and a rapid, exaggerated fall in blood pressure before compensatory reflexes adapt
To avoid this, prazosin should be started at a low dose, preferably at bedtime, with the patient advised to avoid sudden standing after the first dose
