Alpha-1 Selective Antagonists

Question 1

Doxazosin, Tamsulosin, Terazosin
-zosins, -osins
MOA

Answer 1

• HTN: competitively inhibits postsynaptic alpha-1 receptors which result in vasodilation of veins and arterioles and a decrease in total peripheral resistance and BP
• BPH: competitively inhibits postsynaptic apha-1 receptor in prostatic stromal and bladder neck tissues; this reduces the sympathetic tone-induced urethral stricture caused by BPH symptoms

Question 2

Doxazosin, Tamsulosin, Terazosin
-zosins, -osins
Adverse Drug Effects

Answer 2

• fluid retention, nasal congestion, blurred vision, dry mouth, constipation, impotence, urinary frequency, headache, dizziness, fatigue
• risk for significant first-dose orthostatic hypotension (prescribe at nighttime, may experience on next dose after missing one)
• orthostatic hypotension (not Tamsulosin)
• priapism (rare), allergic reactions (rare)

Question 3

Doxazosin, Tamsulosin, Terazosin
-zosins, -osins
Caution and contraindications

Answer 3

• caution in patients with HF< angina, or recent MI
• avoid “-zosins” in the presence of volume depletion
• caution in renal and hepatic impairment
• caution in elderly patients
• limited data in pediatrics
• avoid in pregnancy and lactation