This section is designed to inform professionals.
(Consumers, see Fact Sheet on Mirtazapine)
Available as Remeron
- Centrally active antagonist at pre-synaptic Š1 hetero- and auto-receptors, an action which is thought to increase central noradrenergic and serotonergic neurotransmission.
- Enhances serotonergic neurotransmission via 5-HT1 receptors, and blocks 5-HT2 and 5-HT3 receptors. (5-HT3 blockade is associated with anti-nausea properties.)
- Histamine H1-antagonist which is associated with sedative properties.
- Indicated for use in depression.
- In New Zealand it is not yet funded but may become funded in 2009. If it becomes funded it is likely that to qualify for a full subsidy, 2 other antidepressants must have been trialled unsuccessfully and an application to Pharmac for Special Authority will probably be necessary.
There is limited data available on the safety of Mirtazapine in pregnancy.
- There are case reports of 11 women in which Mirtazapine was used to treat depression or anxiety and Hyperemesis gravidarum (2,3,4). There were no major abnormalities; 1 woman had weight gain of 19kg and developed gestational diabetes; 1 infant developed Persistent Pulmonary Hypertension of the Newborn and required treatment in NICU for 3 days before being discharged healthy. There is no evidence that this was related to the Mirtazapine.
- A prospective, comparative, observational study followed 104 pregnancies in which the foetus was exposed to Mirtazapine, and compared them to a group who took other antidepressants and a group taking known non-teratogens 5. 95% of the women took Mirtazapine in the first trimester; 25% took it throughout pregnancy.
- There was no increase in the rate of major malformations. There was an increase in the rates of spontaneous abortions in the Mirtazapine group compared to women taking non-teratogens but it was not statistically significant (19% vs 10%). This was similar to rates in women taking other antidepressants (17%). There was also an increased risk of preterm births (before 37 weeks) compared to women taking non-teratogens (13% vs 2%).
- A UK study followed up 41 pregnant women who took Mirtazapine in the first trimester(6). There were 8 spontaneous abortions, 8 therapeutic abortions, 24 live births of which 4 were premature. 1 premature baby had a patent ductus arteriosus.
- Another study followed an additional 7 women who were exposed to Mirtazapine either alone or in combination with other drugs, during the first trimester(7). Duration of exposure varied from 1 to 11 weeks. All had healthy babies at term.
- It is unknown whether babies exposed to Mirtazapine towards the end of pregnancy are at risk of the neonatal adaption syndrome associated with the SSRIs. It is suggested that as a precaution, these babies are observed carefully in the post partum.
- There is data on 9 breastfeeding women who were being treated with Mirtazapine suggesting that Mirtazapine is safe in breastfeeding (8,9).
- The mean relative infant dose of 1.9% is below the national level of safety of < 10%
- There were no adverse drug-related effects in the babies and all were achieving developmental milestones. As a precaution, babies should be observed for sedation (10).
1. Remeron data sheet. http://www.medsafe.govt.nz/profs/datasheet/r/remerontab.htm
2. Saks et al. Treatment of depression, anxiety and hyperemesis gravidarum in the pregnant patient. A report of 7 cases. Arch Women Mental Health 2001:3 (4):165-70
3. Rodhe et al. Mirtazapine for treatment resistant hyperemesis gravidarum: rescue of a twin pregnancy. Arch Gynecol Obstet 2003;268 (3):219-21
4. Kesim et al. Mirtazapine use in 2 pregnant women: is it safe? [letter] Teratology 2002;66:204
5. Djulus et al. Exposure to mirtazapine during pregnancy: a prospective, comparatice study of birth outcomes. J Clin Psychiatry 2006;67:1280-4.
6. Biswas et al. The pharmacovigilance of Mirtazapine: results of a prescription event monitoring study on 13,554 patients in England. J Psychopharmacol 2003;17:121-6.
7. Yaris et al. Newer antidepressants in pregnancy: prospective outcome of a case series. Reproductive Toxicology 19 (2004)235-238.
8. Kristensen et al. Transfer of the antidepressant Mirtazapine into breast milk. Br J Clin Pharmacol 63:3 322-327
9. Aichorn et al. Mirtazapine and Breastfeeding. Am L Psychiatry 2004; 161:2325.
10. Hale T W. Medications and Mothersí Milk. Hale Publishing 2006.