Clinical Factors to Predict Methamphetamine Ingestion

Lauren Brewer, MD
Dana Gans, MD
Michele Nichols, MD
William King, DrPH
Kathy Monroe, MD, MSQI
Will Rushton, MD

Our hospital is seeing a number of pediatric patients test positive for methamphetamine on screening urine drug screen (SUDS). Child services become involved when child exposure to methamphetamine is suspected due to its illicit, dangerous nature. SUDS is an immunoassay prone to false positive results from poor antibody specificity. Comprehensive urine drug screen (CUDS) utilizes gas chromatography mass spectrometry and is more reliable but takes weeks to result. Our goal is to identify clinical correlates to risk stratify true ingestion while awaiting CUDS confirmation. Methamphetamine is metabolized into amphetamine and inactive compounds excreted into urine. True methamphetamine positive tests should be amphetamine positive as well. Presenting symptoms consistent with a sympathomimetic toxidrome may increase clinical suspicion for ingestion. Certain lab abnormalities are suspected in methamphetamine ingestions such as elevated creatine kinase (CK), hyperlactatemia, hyperglycemia, and hypokalemia.

This 5 year (2018-2023) retrospective cohort study compares clinical factors of pediatric patients who tested methamphetamine positive on urine drug test at a tertiary medical center. Inclusion criteria required methamphetamine positive SUDS and those without CUDS collection were excluded. Primary outcomes included amphetamine co-positivity, vital sign abnormalities, and hypokalemia. Secondary outcomes included CK elevation, hyperlactatemia, hyperglycemia, and clinical suspicion for ingestion. Age was divided into two groups, 0-5 years (age category 1) and 6-18 years (age category 2). Clinical values compared via logistic regression and utilized corrected Chi square test and T-test of means with Satterthwaite adjustment.

205 patients tested methamphetamine positive on SUDS. Only 52 subsequently had a CUDS obtained. 54% were male and 46% were female. 63% were in age category 1 and 37% in age category 2. 40% were less than 24-months-old. 23% tested in 2023, which was the year with the most cases. 62% of methamphetamine positive SUDS were confirmed with a positive methamphetamine CUDS and 60% were positive for both methamphetamine and amphetamine. This makes 97% of methamphetamine positive CUDS also amphetamine positive. 81% methamphetamine positive CUDS did have amphetamine positive on initial SUDS (Chi-square=25.7, P< 0.005). Age category 1 found to have statistically significant tachycardia when methamphetamine ingestion confirmed with mean heart rate 166 versus 133 when negative (T=-3.3, P=0.003). Age category 2 had clinically significant tachycardia with mean heart rate 104 when methamphetamine positive versus 84 when negative (T=-1.8, P=0.105). 58% age category 1 presented with fussiness, aggression, and agitation. Hypokalemia, CK elevation, hyperlactatemia, and hyperglycemia not statistically significant.

Tachycardia, a marker of sympathomimetic toxicity, was associated with methamphetamine resulting as true positive in ages 0-5 years. A positive amphetamine result on SUDS was also associated with methamphetamine resulting as a true positive, as suspected as amphetamine is a metabolite of methamphetamine. Clinical suspicion for methamphetamine ingestion should increase in patients ages 0-5 years presenting with unexplained fussiness, aggression, and agitation.

1. The presence of aggression, agitation, and fussiness is strongly correlated with methamphetamine ingestion and should increase clinical suspicion.
2. Methamphetamine ingestion correlates with tachycardia.
3. True methamphetamine ingestions should also test positive for its metabolite, amphetamine, on urine drug screen.