SubstanceGuide

Evidence-based drug information & harm reduction

Harm Reduction

Practical, life-saving information. Drug testing kits, dangerous combinations, overdose recognition and response, and naloxone access.

Harm Reduction Notice: This site does not promote drug use. It provides evidence-based information to reduce harm. If you or someone you know is struggling with substance use, call SAMHSA: 1-800-662-4357 (free, confidential, 24/7). In an emergency, call 911. Naloxone saves lives — carry it.

Drug Testing Kits

KitColorDetectsPrimary UseLimitations
MarquisPurple/blackMDMA/MDA, amphetamines, opioids (heroin, morphine)First-line test for MDMA, amphetamines, and opioidsCannot distinguish between MDMA and MDA. Does not detect fentanyl.
MeckeDark blue/greenMDMA/MDA, opioids, 2C-B, DXMConfirmatory test for MDMA (use alongside Marquis)Limited specificity for novel psychoactive substances
MandelinVaries widelyKetamine, PMA/PMMA, amphetamines, opioidsBest test for ketamine identificationColor changes can be subtle and hard to interpret
EhrlichPurpleLSD, psilocybin, DMT (any indole-containing compound)Essential test for LSD blotter (rules out NBOMe)Only confirms presence of an indole; does NOT identify specific compound or dose. NBOMe (dangerous LSD substitute) does NOT react.
Simon'sBlueDistinguishes MDMA from MDA (secondary amines vs primary)Confirmatory: MDMA (blue) vs MDA (no reaction)Must be used after positive Marquis test. Not useful alone.
Fentanyl Test Strips (FTS)Line-based (pregnancy test style)Fentanyl and most fentanyl analogsCritical harm reduction tool for any street drugCannot detect xylazine, nitazenes, or novel synthetic opioids. False negatives possible with uneven distribution in pressed pills ("chocolate chip cookie effect"). Dissolve ENTIRE pill/dose in water and test the solution.
Xylazine Test StripsLine-basedXylazine (tranq)Supplementary to fentanyl test strips for opioid supplyOnly 49% sensitivity (misses about half of xylazine-positive samples). Newer strips improving but not yet widely available.

Dangerous Drug Combinations

CombinationRisk LevelAction
Opioids + BenzodiazepinesFATALAvoid completely. Additive respiratory depression.
Opioids + AlcoholFATALNever combine. Even moderate alcohol + opioids can be lethal.
MAOI + SSRI/SNRIFATALSerotonin syndrome. 2-week washout between drugs.
Alcohol + BenzodiazepinesFATALBoth enhance GABA-A. Synergistic respiratory depression.
GHB + Alcohol or BenzosFATALGHB has narrow therapeutic window. Never combine with CNS depressants.
Stimulants + MAOIsFATALHypertensive crisis. Avoid all stimulants if on MAOIs including ayahuasca.
Cocaine + AlcoholDANGEROUSForms cocaethylene. More cardiotoxic than either alone.
Psychedelics + LithiumRISKYSeizure risk. Do not take psychedelics while on lithium.

Overdose Response

  1. Call 911 immediately — Good Samaritan laws protect you in most states
  2. Administer naloxone if opioid overdose suspected — nasal spray (Narcan) or intramuscular
  3. Perform rescue breathing — 1 breath every 5 seconds if not breathing
  4. Place in recovery position — on their side to prevent aspiration
  5. Stay with them — naloxone wears off in 30-90 min; the opioid may outlast it
  6. Give second naloxone dose if no response after 2-3 minutes

Where to Get Naloxone

Emergency Numbers