Reduced retention makes buprenorphine a poor second to methadone in pregnancy.
Jones HE, Kaltenbach K, Heil SH, Stine SM, Coyle MG, Arria AM, O'Grady KE, Selby P, Martin PR, Fischer G. Neonatal Abstinence Syndrome after Methadone or Buprenorphine Exposure. NEJM 2010; 363:2320-2331
Dear Colleagues,
These authors assessed 1074 pregnant women from clinics in Austria, Canada and the USA for this comparison of methadone and buprenorphine regarding neonatal abstinence syndrome (NAS). There were 250 who declined to participate and another 650 did not fit inclusion criteria (alcohol, benzo use, medical conditions, for example) leaving 175 in the randomised comparison groups, blinded by a morphine wash-out period in hospital and use of ‘double dummy’ placebo. Pure buprenorphine (Subutex) was used to avoid prenatal exposure to naloxone (Suboxone is contraindicated in pregnancy). Over $1000 was available to subjects contingent on clear urine toxicology during the trial.
There were two peri-natal deaths reported from those who remained in the study, one from each group. There were two miscarriages (both in the MMT group). “The percentage of neonates requiring NAS treatment did not differ significantly between groups (P = 0.26), nor did the groups differ significantly with respect to the peak NAS score (P = 0.04) or head circumference (P = 0.04).” However, two other primary outcomes were significantly better in the buprenorphine group: (1) quantities of morphine used for neonatal abstinence syndrome (NAS) and (2): ‘total hospital stay’. The prognostic significance of these outcomes is unknown to my best knowledge.
The numbers of enrolled subjects were not large enough to show anything but very major outcome effects as being statistically significant. Previous experience has consistently shown only modest differences between methadone and buprenorphine regarding neonatal outcomes. Hence this trial was under-powered on the numbers to find minor differences to statistical significance.
Aside from the unsurprising neonatal outcomes, there were some dramatic and remarkable maternal findings which are mentioned but not brought to the prominence they deserve in my view. These differences are so great that they may even invalidate the neonatal findings (for example if those with high tolerance or rapid metabolism were more likely to drop out).
To my mind the two most important findings of the study are as follows:
The methadone group (n=89) had 16 drop-outs (18%) while the buprenorphine group (n=86) had 28 drop-outs (33%) [p=0.02]. Even more dramatic, of the 16 methadone drop-outs, 2 were due to ‘dissatisfaction with the medication’ while the corresponding number for the buprenorphine candidates was 20, a massive difference. These findings are discussed in the text but should probably also be enshrined in the title of the article. There is no point in having favourable neonatal outcomes if a third of the mothers have left treatment before term.
Even with its failings, I believe that this study provides the most persuasive evidence to date showing the safety and effectiveness of methadone in pregnancy. Indeed, it clearly demonstrates that, in the absence of contraindications, methadone should be the first line drug for opiate dependence in pregnancy (as in the non-pregnant). Yet despite their finding that almost twice as many women dropped out in the buprenorphine group, these authors state, somewhat clumsily: “Although there were no significant differences in overall rates of NAS among infants exposed to buprenorphine and those exposed to methadone, the benefits of buprenorphine in reducing the severity of NAS among neonates with this complication suggest that it should be considered a first-line treatment option in pregnancy.”
Rather than an option, “first line” status implies an obligation in my book. Since buprenorphine is the only alternative medication licensed for opioid dependence then it is obviously an ‘option’, if a somewhat less effective one. This RCT confirms that during pregnancy, consistent with the existing body of research evidence, (pure) buprenorphine should be the second line drug and only used when methadone is found to be clinically inappropriate. I believe that it is unethical to prescribe Suboxone (buprenorphine/naloxone).
Comments by Andrew Byrne ..
http://methadone-research.blogspot.com/
