Atazanavir / ritonavir

Terazosin

Use with caution.

No pharmaceutical opinion available for this interaction.

Mechanism

Atazanavir / ritonavir can inhibit the metabolism (CYP 3A4) and increase the plasma concentration of Terazosin.

Atazanavir / ritonavir

Pharmacodynamic effects

Recommendations

Alternative solution(s)

Terazosin

Pharmacodynamic effects

Possible increase of adverse effects including hypotension.

Clinical significance unknown.

Recommendations

Use this combination with caution.

Start with a lower dose and adjust the dosage as a function of efficacy and the occurence of adverse effects.

Monitor effect on blood pressure and the occurrence of orthostatic hypotension.

In patients already being treated with this combination and tolerating it, if deemed appropriate, keep actual treatment and exercise close monitoring of adverse effects.

A decrease in dosage may be necessary.

Alternative solution(s)

Monitor

Side effects of terazosin: dizziness, asthenia, orthostactic hypotension, tachycardia, syncope, vertigo and headaches.

Tests

Pharmacokinetic parameters

Comment

In a study (n=24), terazosin was administered concomitantly with verapamil, a CYP3A4 inhibitor. Terazosin AUC increased by 24% with associated increases in Cmax by 25% and Cmin by 32%. Statistically significant differences were not found in verapamil levels. Cases of symptomatic hypotension, and sometimes even tachycardia, have been observed.

Reference
  • 2558
    Terazosin (Hytrin), BGP Pharma, Québec, Canada, 9 avril 2015.