Is methamphetamine blood concentration in emergency department patients associated with the clinical picture?

Abstract

Aims: This study aimed to describe clinical features and outcomes of patients presenting to the emergency department with analytically confirmed methamphetamine intoxication, to determine the blood concentration of methamphetamine and to test its association with clinical findings.

Design: The Western Australian Illicit Substance Evaluation (WISE) study is a prospective observational cohort study.

Setting: Royal Perth Hospital Emergency Department, Perth, Australia, between 2016 and 2018.

Participants: Patients suspected to be intoxicated with a stimulant, hallucinogenic or cannabinoid substance and who required intravenous access or blood tests as part of standard care. Those predominantly alcohol intoxicated, behaviourally disturbed or opioid intoxicated were excluded. The 431 participants with detectable methamphetamine (> 0.001 mg/l) included in this analysis had a mean age of 33.2 (9.4) years and 286/431 (66.4%) were male.

Measurements: Concentration was reported for methamphetamine and other illicit drugs detected. Univariate associations of symptoms and signs, and physiological and laboratory parameters with methamphetamine concentration were determined and used to develop a multivariable model.

Findings: The median concentration of methamphetamine was 0.12 mg/L [Q1,Q3: 0.05, 0.27]. Psychotic symptoms were seen in 265/431 (61.5%) patients and intravenous or intramuscular sedation was required in 280/431 (65.0%). Mean heart rate was elevated at 105.9 (21.5) beats per minute, but other mean or median physiological parameters were within normal limits. A multivariable model showed that methamphetamine concentration was 27% lower in males (P = 0.026), 60% higher in those with palpitations (P = 0.013), 62% higher in those with choreoathetoid movements (P = 0.002) and increased by 1% for each unit (μg/L) increment in creatinine (P = 0.001).

Conclusions: In a cohort of emergency department patients with methamphetamine exposure, a multivariable model inferred a significant association between higher methamphetamine concentration and female sex, the presence of palpitations and choreoathetoid movements and creatinine concentration. The model showed no significant association with agitation, psychotic symptoms or other physiological or clinical parameters.

Keywords: amphetamines; emergency medical services; illicit drugs; methamphetamine; psychosis; substance‐related disorders; synthetic drugs.