Background/Purpose
Ethanol co-administered with immediate-release dl-methylphenidate (dl-MPH) or dexmethylphenidate (d-MPH) significantly increases the geomean maximum plasma concentration (Cmax) of d-MPH 22% and 15%, respectively, and elevates overall drug exposure and psychostimulant effects. We asked the question: Are these ethanol-MPH interactions based more fundamentally on: (1) inhibition of post-absorption d-MPH metabolism or (2) acceleration of MPH formulation gastric dissolution by ethanol in the stomach? This was investigated using the pulsatile, distinctly biphasic, Spheroidal Oral Drug Absorption Systems of dl-MPH and d-MPH.
Methods/Procedures
In a randomized, 4-way crossover study, fourteen healthy subjects received pulsatile dl-MPH (40 mg) or d-MPH (20 mg), with or without ethanol (0.6 g/kg), dosed 4 hours later. These 4 hours allowed the delayed-release second MPH pulse to reach a more distal region of the gut to preclude gastric biopharmaceutical influences. Plasma was analyzed using a highly sensitive chiral method. Subjective/physiological effects were recorded.
Findings/Results
Ethanol increased the second pulse of d-MPH Cmax for dl-MPH by 35% (P < 0.01), and the partial area under the curve (pAUC4–8h) by 25% (P < 0.05). The respective values for enantiopure d-MPH were 27% (P = 0.001) and 20% (P < 0.01). The carboxylesterase 1-mediated transesterification metabolite ethylphenidate served as a biomarker for co-exposure. Ethanol significantly potentiated stimulant responses to either formulation.
Implications/Conclusions
These findings support drug dispositional interactions between ethanol and MPH as dominant over potential biopharmaceutical considerations. Understanding the pharmacology underlying the frequent co-abuse of MPH-ethanol provides rational guidance in the selection of first-line pharmacotherapy for comorbid ADHD-alcohol use disorder.