Frågedatum: 2001-03-05
RELIS database 2001; id.nr. 17505, DRUGLINE
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Is there any known risk of interaction between Viagra (sildenafil) and Remeron (mirtazapine)?/nA ma



Fråga: Is there any known risk of interaction between Viagra (sildenafil) and Remeron (mirtazapine)? A man with hypertension and slightly reduced renal function is suffering from total erectile dysfunction and is also treated with mirtazapine. His physician is considering treatment with Viagra 50 mg (sildenafil) but is concerned about the risk of a possible interaction since both mirtazapine and sildenafil are metabolised by CYP3A4. Concomitant drugs: Tenormin (atenolol) 25mgx1.

Sammanfattning: There is no information on drug interactions between mirtazapine and sildenafil. There is a slight theoretical risk of pharmacokinetic drug interactions since both drugs are metabolised by the CYP3A4.

If co-medication is initiated, monitoring of mirtazapine plasma levels is recommended. The dose of sildenafil can be adjusted based on the clinical effect. Dose titration is recommended.

Svar: There is no information on drug interactions between mirtazapine and sildenafil in Medline, Embase, Drugline or standard pharmacological literature.

In vitro studies have shown that sildenafil is extensively metabolised by cytochrome P450 isoenzyme CYP3A4 and to some extent by CYP2C9 (1-2).

The antidepressant mirtazapine is mainly metabolised by the same cytochrome P450 isoenzyme CYP3A4 (3).

In an open trial, 14 patients were treated with oral sildenafil 50 mg for antidepressant-induced sexual dysfunction (4). Twelve of the patients were treated with SSRI and two with mirtazapine. Oral sildenafil treatment appeared to be well tolerated and there were no signs of increased adverse reactions.

There is no theoretical ground for a pharmacodynamic interaction on receptor or transduction levels.

There is a theoretical risk of pharmacokinetic drug interactions since both drugs are metabolised by the same cytochrome isoenzyme CYP3A4. However, since neither of these two drugs is a potent inhibitor of CYP mediated drug metabolism the risk is probably small (5). Sildenafil has a half-life of 3-5 hours and is given as single doses and is therefore unlikely to affect steady state plasma concentration of mirtazapine.

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