Methylphenidate intoxications in children and adults: exposure circumstances and evidence-based dose threshold for pre-hospital triage.

Context: Methylphenidate intoxications mostly have a relatively mild course, although serious complications can occur.

Objective: We aimed to characterize methylphenidate exposures and reassess our current dose threshold for hospital referral (2 mg/kg).

Methods: In a prospective follow-up study, we analysed 364 consecutive methylphenidate exposures that were reported to the Dutch Poisons Information Center. Patients and/or physicians were surveyed by telephone using standardized questionnaires. Three physicians independently scored the observed severity of the intoxication of each patient as 'no/mild' (observation at home) or 'moderate/severe' (hospital referral necessary).

Results: Unintentional exposures (40%) mostly occurred at home involving the patients' own medication or those from a family member. Compared to unintentionally exposed patients, intentionally exposed patients were exposed to relatively high methylphenidate doses (3.1 vs 1.6 mg/kg), more often used immediate release methylphenidate formulations (62 vs 34%) and more frequently had concomitant exposures (71 vs 17%). Severe symptoms like convulsions or coma were reported only in patients with concomitant exposures. Following exposure to methylphenidate only (i.e. no concomitant exposures), the most commonly reported symptoms were dry mucosa, headache, agitation, sleepiness and tachycardia. Our results show that the reported methylphenidate dose is predictive of the observed severity of the intoxication and can therefore aid in pre-hospital triage.

Conclusion: We increased our current dose threshold for hospital referral from 2 to 3 mg/kg. In addition, we will refer patients at lower doses when clinical symptoms indicate the need for hospital referral. Application of this new dose threshold optimizes triage, thereby reducing unnecessary hospital referral and thus costs, without jeopardising patient safety.