Mirtazapine and Sexual Side Effects
Mirtazapine has minimal to no sexual side effects and may actually improve sexual function in depressed patients, making it an excellent alternative for patients experiencing sexual dysfunction from other antidepressants. 1
Sexual Function Profile
Mirtazapine stands out among antidepressants for its favorable sexual side effect profile:
In depressed women treated with mirtazapine, sexual desire improved by 41%, arousal/lubrication by 52%, and ease/satisfaction of orgasm by 48%. 2
In depressed men, desire improved by 10%, arousal/erection by 23%, and ease/satisfaction of orgasm by 14%. 2
When patients with SSRI-induced sexual dysfunction were switched to mirtazapine, 58% had complete return of normal sexual functioning and another 11% reported significant improvement, while all maintained their antidepressant response. 3
Mechanism Explaining Low Sexual Side Effects
The favorable sexual profile is explained by mirtazapine's unique mechanism of action:
Mirtazapine blocks postsynaptic 5-HT2 and 5-HT3 receptors, which are responsible for sexual dysfunction seen with SSRIs. 4
It enhances noradrenergic and specific 5-HT1 receptor-mediated serotonergic neurotransmission without the broad serotonergic effects that cause sexual problems. 5, 4
Unlike SSRIs, mirtazapine does not inhibit serotonin reuptake, avoiding the excessive serotonergic stimulation that impairs sexual function. 6
Comparison to Other Antidepressants
When considering sexual side effects across antidepressants:
Paroxetine has the highest sexual dysfunction rate at 70.7% among all SSRIs. 1
Bupropion remains the single best option when sexual function is the primary concern, with an 8-10% sexual dysfunction rate. 1
Bupropion has significantly lower rates of sexual adverse events than fluoxetine or sertraline. 7
Paroxetine has higher rates of sexual dysfunction than fluoxetine, fluvoxamine, nefazodone, or sertraline. 7
Important Side Effects to Consider
While sexual side effects are minimal, mirtazapine has other notable adverse effects:
Weight gain is a primary concern, as mirtazapine causes more weight gain than sertraline, trazodone, or venlafaxine. 8, 1
Sedation occurs commonly, especially at lower doses, though this can be therapeutically beneficial for patients with insomnia. 1
The most common side effects include drowsiness (23%), excessive sedation (19%), dry mouth (25%), increased appetite (11%), and weight gain (10%). 6
Dosing Recommendations
Start mirtazapine at 7.5 mg at bedtime, with a maximum dose of 30 mg at bedtime. 1
The recommended initial dosage is 15 mg once daily at bedtime, with an effective daily dosage range of 15-45 mg. 4
When switching from SSRIs due to sexual dysfunction, mirtazapine can be titrated from 7.5 mg to 45 mg daily as tolerated. 3
Clinical Application
For patients experiencing sexual dysfunction on SSRIs or SNRIs, switching to mirtazapine is an evidence-based strategy that preserves antidepressant efficacy while restoring sexual function. 3 The main trade-off is potential weight gain and sedation, which should be discussed with patients before switching. 1, 6