Toxicology

Serum fentanyl concentrations attain a range of 0.3 – 1.2 µg/L within 24 hours after application of a 25 µg/hr transdermal patch with serum levels inceasing up to 3.8 µg/L with use of a 100 µg/hr patch. (Baselt, Disposition of Toxic Drugs and Chemicals in Man, Eighth Edition, 2008). 

Therapeutic monitoring of gabapentin is not recommended. It may accumulate in renal failure.

Therapeutic range: 2 – 20 mg/L.

(Source: Therapeutic Drug Monitoring in Laboratory Medicine. Hallworth & Watson)

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 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.

0.02 - 0.25 mg/L

Toxicity associated with MDMA levels > 0.35 mg/L & MDA levels > 1.5 mg/L.  (Schulz et al. Critical Care 2012, 16:R136).

No reference range available.