In forensic toxicology, cocaine is better known for its powerful stimulating effects of nervous system and its high potential for recreational abuse, than for his therapeutic use. However, cocaine is still use as a topical anesthetic and peripheral vasoconstrictor in surgeries of eye, ear, nose and throat. Last decade, an increase of the presence of cocaine and metabolites in blood samples of drivers suspected to drive under the influence of drugs (DUID) was observed in Switzerland (Augsburger et al., Forensic Sci Int 153 (2005) 11-15; Senna et al., Forensic Sci Int 198 (2010) 11-16). Observed blood concentration ranges of cocaine and benzoylecgonine were 10-925μg/L and 20-5200μg/L, respectively. Since 2005, zero-tolerance approach was introduced in the Swiss legislation for different substances, especially cocaine (analytical cutoff: 15μg/L). Thus, the interpretation often amounts to determine if the concentration is situated above or under the limit. However, it is important for the interpretation to take into account the context and to be critical with the obtained results, at the risk of ending in erroneous conclusions.

Systematical toxicological analyses were performed on blood and urine, if available, for 5 DUID cases, as already published (Augsburger et al., Forensic Sci Int 153 (2005)). Positive results were confirmed and drugs were quantified in biological samples by GCMS, GC-MS/MS or LC-MS/MS.

Administration of cocaine after traffic accident was identified in five cases. All people were admitted to the emergency room because of severe trauma. Maxillofacial surgery was done shortly after admission to the emergency room, involving use of nasal application of cocaine (swab). For all cases, use of cocaine swab was not mentioned in the document filled by the police and by medical staff requested for blood and urine sampling. The information was obtained retrospectively after consultation of the medical records, without precise indication of the application time or dose. Case 1. A 83-year old man (pedestrian) was hit by a car. Blood (+11h after the accident): cocaine (16μg/L), benzoylecgonine (370μg/L). Urine: cocaine (1700μg/L), benzoylecgonine (560μg/L). Case 2. A 84-year old woman (pedestrian) was hit by a car. Blood (+1.5h after the accident): cocaine (230μg/L), benzoylecgonine (370μg/L). Urine was not available. Hair (+4 months after the accident): segment 1 (0-2cm), cocaine not detected; segment 2 (2-4cm), cocaine: <0.5ng/mg. Case 3. A 66-year old man was involved in a car/car accident. He died 2 hours and 5 minutes after the crash. Blood (+1.5h after the accident): cocaine and metabolites not detected. Blood (+2h after the accident): cocaine (1750μg/L), benzoylecgonine (460μg/L). Blood (post-mortem): cocaine (370μg/L), benzoylecgonine (200μg/L). Urine (+1.5h after the accident): cocaine not detected. Case 4. A 57-year old woman on a motor scooter was hit by a car. She died 2 hours and 10 minutes after the crash. Blood (+0.5h after the accident): cocaine and metabolites not detected. Urine (post-mortem): cocaine (<20μg/L), benzoylecgonine (120μg/L). Case 5. A 30-year old man was involved in a car accident. Blood (+4h after the accident): cocaine (29μg/L), benzoylecgonine (< 20μg/L). Urine (+4h after the accident): cocaine and metabolites not detected. Ethanol (1,32g/kg) and cannabinoids (THC (2,0μg/L), THCCOOH (38μg/L)) were also detected in blood.

To our knowledge, this is the first description of DUID cases involving therapeutic use of cocaine after an accident. These results indicate that even if a per se law is effective for prosecution case of DUID, a critical interpretation of the results is always needed, especially if a medical intervention occurs after an accident.