Toxicology

High dose therapeutic use of diphenhydramine associated with concentrations of up to 0.3 mg/L. Toxicity associated with concentrations > 1 mg/L.  (Schulz et al. Critical Care 2012, 16:R136).

Positive results represent concentrations of drugs above the European Workplace Testing Thresholds with the exception of benzodiazepines.  We have lowered the cut off for this class of drug to 10ug/L to increase the detection of benzodiazepines.

Bromazolam, Etizolam, Flualprazolam, Flubromazolam, THC-COOH glucuronide, Buprenorphine glucuronide and Norbuprenorphine glucuronide will be qualitative only.

Drugs without a cut-off have been assigned one based on chemically similar compounds.

Please contact laboratory for interpretation.

Therapeutic range = 120 - 500 ug/L (sum of fluoxetine and desmethylfluoxetine)

Gamma-hydroxybutyrate (GHB) has been employed as an anaesthetic agent but is now more widely used and abused for its sedative properties. Toxic effects (euphoria, dizziness and unconsciousness) usually occur around 15 minutes post ingestion and last on average for about 3 hours. It has been found that blood concentrations above 260 mg/L were associated with deep sleep, 156 – 260 mg/L with moderate sleep, 52 – 156 mg/L with light sleep and levels less than 52 mg/L with wakefulness.

Therapeutic concentrations of imipramine range between 50 to 150 ug/L, with the total sum of imipramine and desipramine between 150 and 300 ug/L. 

Therapeutic use of ketamine (i.v) for sedation is effective at average concentrations >0.6 mg/L. (Clarke's Analysis of Drugs & Poisons, Third Edition)

Normal values: <0.24 umol/L

Desirable values in children: <0.24 umol/L

Occupational Certification Limit for women of reproductive capacity: 1.45 umol/L

Occupational Certification Limit for males (age 18+): 2.90 umol/L

Please note that the normal values have been decreased as of 2018 to bring us in-line with CDC recommendations.

There is no evidence to justify monitoring of Levetiracetam other than to assess adherence, though a range of 6 – 20 mg/L has been suggested. Renal excretion means that the plasma half-life is longer in the elderly. Dose reduction is necessary at GFR < 60 mL/min/1.73 m².