"Metformin may be effective in decreasing weight gain associated with atypical antipsychotic use and is well tolerated by children and adolescents with ASD [autism spectrum disorder]."
So said the paper by Evdokia Anagnostou and colleagues  (open-access) tackling an increasingly important health issue related to the pharmacological 'management' of some aspects of some autism.
Metformin is the treatment of choice when it comes to the management of type 2 diabetes (the one where "the pancreas doesn't produce enough insulin or the body's cells don't react to insulin"). It is thought to work by helping the liver to stop producing new glucose and also helping insulin carry more glucose into muscle cells more effectively. Alongside, an increasing body of research has also suggested that metformin might be a useful intervention measure to offset one of the quite well-known side-effects associated with various antipsychotic agents: weight gain.
So Anagnostou et al set about looking to "assess the safety, tolerability, and efficacy of metformin to decrease weight gain associated with the use of atypical antipsychotic medication in children with ASD." They did this using the gold-standard in clinical trial designs: the "double-blind, placebo-controlled, randomized clinical trial" where some 60 children and young adults diagnosed with an ASD and receiving a stable dose of an atypical antipsychotic received either metformin (Riomet) or a placebo over the course of 16 weeks. "The primary outcome measure was change in body mass index (BMI) z score during 16 weeks of treatment. Secondary outcomes included changes in additional body composition and metabolic variables." The study protocol was also registered with ClinicalTrials.gov.
As per the opening sentence, there were some important differences in body mass index (BMI) z-scores suggestive that compared with a placebo, those prescribed metformin saw decreases in weight gain. The range of decrease in BMI were in some cases between about 8-9% over the course of the 16 week study period (most of the benefits seemed to be apparent after about 8 weeks of metformin use). Insofar as those secondary variables also examined during the course of the study (glucose levels, insulin, triglycerides, etc.) no significant differences were noted across the study. When it came to the important issue of side-effects, the authors noted that gastrointestinal (GI) effects seemed to be more apparent in the group taking metformin during treatment days. Aside from that, short-term side-effects seemed to be few and far between.
The authors note that their trial "did not address the question of whether coadministration of metformin at the onset of atypical antipsychotic use prevents initial weight gain" but rather whether metformin use after weight gain associated with antipsychotic use could be effective. In that light, these are important results that very much require further independent investigation.
Quite a few times on this blog I've talked about how the physical health of those on the autism spectrum is sometimes neglected as a function on the focus on mental health or behaviour. There is a growing recognition that autism, or at least some of the important comorbidities associated with autism, might somehow predispose to a more sedentary lifestyle and the accompanying health issues that this can bring. Throw into the mix the possibility that some of the pharmacotherapy used in autism might also contribute to something like weight issues , and you have a recipe for some pretty severe health issues potentially building up in later life. These latest findings are therefore welcomed as a way to potentially lower the burden of an elevated BMI in cases where such medication is prescribed.
I do have questions however about this approach and how one perhaps needs to be slightly cautious about slipping into the old 'medication to tackle medication side-effects' routine with autism in mind (something noted in an accompanying editorial to the Anagnostou study). Metformin, whilst a very useful drug, is not without side-effects as was noted in the Anagnostou study and given the quite high rates of GI issues noted in cases of autism (see here), one really does not want to make this any worse. I would also like to see more data on the use of metformin in antipsychotic-induced weight gain in autism with a focus on other parameters thought to be altered by such antipsychotic use such as the issue of prolactin levels for example (see here). Yes, there is data to suggest that metformin might more generally work on prolactin levels too  but does this similarly apply to children on the autism spectrum? And then also there is the issue of sleep ...
 Anagnostou E. et al. Metformin for Treatment of Overweight Induced by Atypical Antipsychotic Medication in Young People With Autism Spectrum Disorder. JAMA Psychiatry. 2016. Aug 24.
 Shedlock K. et al. Autism Spectrum Disorders and Metabolic Complications of Obesity. Journal of Pediatrics. 2016. Sept 2.
 Krysiak R. et al. The effect of metformin on prolactin levels in patients with drug-induced hyperprolactinemia. Eur J Intern Med. 2016 May;30:94-8.
 Kajbaf F. et al. The relationship between metformin therapy and sleep quantity and quality in patients with Type 2 diabetes referred for potential sleep disorders. Diabet Med. 2014 May;31(5):577-80.
Anagnostou E, Aman MG, Handen BL, Sanders KB, Shui A, Hollway JA, Brian J, Arnold LE, Capano L, Hellings JA, Butter E, Mankad D, Tumuluru R, Kettel J, Newsom CR, Hadjiyannakis S, Peleg N, Odrobina D, McAuliffe-Bellin S, Zakroysky P, Marler S, Wagner A, Wong T, Macklin EA, & Veenstra-VanderWeele J (2016). Metformin for Treatment of Overweight Induced by Atypical Antipsychotic Medication in Young People With Autism Spectrum Disorder: A Randomized Clinical Trial. JAMA psychiatry PMID: 27556593