Atazanavir / ritonavir

Mirtazapine

Dose adjustment and closer monitoring are required.

No pharmaceutical opinion available for this interaction.

Mechanism

Atazanavir / ritonavir can inhibit the metabolism (CYP 3A4 and 2D6) and increase the plasma concentration of Mirtazapine.

Atazanavir / ritonavir

Pharmacodynamic effects

Recommendations

Alternative solution(s)

Mirtazapine

Pharmacodynamic effects

Possible increase of adverse effects.

Increased risk of an extension of the QT interval.

Recommendations

Start with the lowest dose possible, or in patients already on treatment, a dose reduction may be necessary.

Monitor closely clinical efficacy and appearance of adverse effects.

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

Alternative solution(s)

Monitor

Mirtazapine adverse effects: drowsiness, dry mouth, increased appetite, gain of weight, constipation, dizziness and headaches.

QT interval in patients with possible electrolyte disorders or other risk factors for QT prolongation.

Tests

Pharmacokinetic parameters

Comment

Mirtazapine product monograph recommends caution when co-administered with CYP2D6 inhibitors or strong CYP3A4 inhibitors.

Effets indésirables de la mirtazapine : somnolence, bouche sèche, augmentation de l’appétit, gain pondéral et céphalées.

Reference
  • 2580
    Mirtazapine (Remeron), Merck, Quebec, Canada, 16 Mars 2015.
  • 2626
    Spina E, Trifirò G, Caraci F. Clinically significant drug interactions with newer antidepressants. CNS Drugs. 2012 Jan 1;26(1):39-67.
  • 122
    Ritonavir (Norvir), Corporation AbbVie, Quebec, Canada, 25 septembre 2018.
  • 2839
    Siccardi M, Marzolini C, Seden K et al. Prediction of drug-drug interactions between various antidepressants and efavirenz or boosted protease inhibitors using a physiologically based pharmacokinetic modelling approach. Clin Pharmacokit 2013; 52:582-592.