Diazepam: general

Diazepam is a benzodiazepine [1][2]. It works by calming abnormal overactivity in the brain [2]. It's prescribed for anxiety, alcohol withdrawal agitation, muscle spasms and stiffness from nerve disorders, and seizures [1][2]. It's long-acting, and alongside its calming and anti-seizure effects it produces sedation, muscle relaxation, and amnesia — it can blank out memory of what happens while you're on it [3].

The two things that matter most before anything else:

Mixing sedatives increases overdose risk. As with benzodiazepines generally, combining diazepam with other sedating drugs, especially opioids, substantially increases the risk of accidental overdose and fatal respiratory depression [4]. Don't stack sedatives — and alcohol is one. In July 2021, 70% of expected fentanyl samples contained one or more nonmedical benzodiazepines [5].

Test strips can miss benzodiazepines. Benzodiazepine test strips have a false negative rate, with sensitivity to etizolam measured at 50% to 70% [5]. Benzodiazepines generally don't dissolve well in water, which testing requires [5]. A clean strip result doesn't rule out a benzodiazepine being present.

If someone is overdosing on a depressant, the signs include shallow, erratic, or stopped breathing, blue lips or fingernails, unconsciousness, snoring or gurgling, and a slow or erratic pulse [6][8]. Naloxone reverses opioid effects but not the sedation from a benzodiazepine [5] — give it anyway if opioids might be involved, but don't let it stand in for calling for help. Roll them into the recovery position, don't leave them alone, call emergency services, and give CPR if they've stopped breathing [7][8].

References

1. Diazepam - StatPearls - NCBI Bookshelf — NCBI / StatPearls
2. Diazepam: MedlinePlus Drug Information — National Library of Medicine / MedlinePlus
3. diazepam | Ligand page | IUPHAR/BPS Guide to PHARMACOLOGY — IUPHAR/BPS Guide to PHARMACOLOGY
4. Anxiolytics and Sedative-Hypnotics Toxicity - StatPearls — NCBI Bookshelf (US National Library of Medicine)
5. Risks and Harms Associated with the Nonmedical Use of Benzodiazepines in the Unregulated Drug Supply in Canada — Canadian Centre on Substance Use and Addiction (CCSA)
6. Depressant overdose signs - Rapid Action Drug Alerts and Response (RADAR) — Public Health Scotland
7. Depressants Overdose Response — Indiana Department of Health
8. Overdose Response Fact Sheet: Depressants — International Overdose Awareness Day