What is known about the use of ondansetron during pregnancy?/nThe question concerns a woman pregnan

Fråga: What is known about the use of ondansetron during pregnancy?<br><br>The question concerns a woman pregnant in week 16-17 who has been treated with ondansetron (Zofran).

Sammanfattning: Available data do not indicate any major risk of malformations from ondansetron. However, ondanstron should generally be avoided during pregnancy, as the documentation is still to limited to ensure the safety of the drug, which is known to cross the placenta. Ondansetron is not approved for the treatment of pregnancy nausea. Occasional intake of ondansetron during pregnancy is not an indication for abortion.

Svar: The question about the use of ondansetron in pregnancy has previously been answered in Drugline. At that time, there were four case reports with normal pregnancy outcome and a small pilot study on 15 women with unknown pregnancy outcome published (1). Since then, more data on the use of ondansetron during pregnancy has been published.<br><br>A prospective observational study has been performed among women consulting a nausea and vomiting help line, the Motherrisk Program or the Mothersafe Program. Three groups, with 176 women in each, were studied. The first group included women, less than three months pregnant, who were prescribed ondansetron, the second included women treated with other antiemetics and the third included woman treated with other drugs considered safe in pregnancy and those taking no drugs. In the ondansetron group there were 169 live births, 5 miscarriages and 6 major malformations. Among the women in the second and third group there were 160 and 162 live births, 13 and 14 miscarriages respectively. Three major malformations were observed in each of these groups. There was no statistically significant difference between the groups in any of the studied parameters. Three cases of minor-moderate hypospadias were observed in the ondansetron group, which is higher than the expected number (1 of 300 boys) (2).<br><br>In the Swedish medical birth register, there are 53 ondansetron exposed children. Two were born with malformations, none with hypospadia (3).<br><br>A woman with hyperemesis gravidarum, in week 12 of pregnancy, was successfully treated with intravenous ondansetron 8mg x3 for 7 days and oral ondansetron for 2 days. The baby was delivered by caesarean section in week 35 due to premature rupture of the membranes. The baby was healthy, without malformations and developed normal at one year of age (4).<br><br>The placental transfer of ondansetron has been studied in 41 women. All received ondansetron 8mg x3 before elective surgical abortion in the first trimester. The drug concentration in fetal tissue was 41% of the concentration in maternal plasma, and significant amounts of ondansetron were present in all embryonic compartments (5).<br><br>Ondansetron does not appear to cause any major risk of malformations. However, a small increase in the risk of hypospadia cannot be excluded. The fusion of the urethral folds occurs in week 8-16 and exposure to drugs associated with hypospadia during this period increases the risk (6).<div id="referenser" style="display:none;">Drugline nr 13402 (year 1998)<br>Einarson A, Maltepe C, Navioz Y, Kennedy D, Tan MP, Koren G. The safety of ondansetron for nausea and vomiting of pregnancy: a prospective comparative study. BJOG 2004;111(9):940-3.<br>Ondansetron. Läkemedel och fosterskada. Uppdated 2003-12-29. Available from: URL: http://www.janusinfo.se<br>Siu SS, Yip SK, Cheung CW, Lau TK. Treatment of intractable hyperemesis gravidarum by ondansetron. Eur J Obstetr Gynecol Reprod Biol 2002;105:73-4.<br>Siu SS, Chan MT, Lau TK. Placental transfer of ondansetron during early human pregnancy. Clin Pharmacokinet 2006;45(4):419-23.<br>Hypospadi. Läkemedel och fosterskada. Uppdated 2003-12-29. Available from: URL: http://www.janusinfo.se</div>