Decreased serum glucose levels after initiation of methylphenidate in a patient status post-cerebellar tumour resection: a potential interaction with glipizide.

Pharmacological intervention with methylphenidate to address the neurobehavioural deficits associated with various neurological disorders has increased during the past decade. One potential effect of methylphenidate use is its possible influence on serum glucose. This case report illustrates a significant post-intervention decrease in blood glucose levels subsequent to initiation of methylphenidate to address neurocognitive deficits, status post-acute cerebellar tumour resection, in a 38-year-old female with type 2 diabetes mellitus. A decrease of 26% in serum glucose values was seen from the pretreatment to the post-treatment phase (p = 0.003). Hypotheses concerning drug-drug interactions are offered to explain this unusual outcome. Although anecdotal, this finding has important implications for use of methylphenidate in the treatment of persons with diabetes and should be considered in light of the recent vote of the Drug Safety and Risk Management Advisory Committee of the US FDA urging 'black box' warnings on stimulant medications used to treat attention-deficit/hyperactivity disorder.