Scientific Principles · 3 min read
Substance Classes and Their Effects
A useful rule: withdrawal signs are generally the opposite of intoxication signs (a "rebound" effect).
Classes at a Glance
| Class | Examples | Intoxication signs | Withdrawal signs | Key risks |
|---|---|---|---|---|
| Alcohol | Beer, wine, liquor | Slurred speech, incoordination, unsteady gait, nystagmus, impaired memory, stupor or coma | Tremor, sweating, rapid pulse, raised blood pressure, anxiety, insomnia, nausea, transient hallucinations, seizures, delirium tremens | Fatal withdrawal; respiratory depression with other depressants; liver disease; Wernicke–Korsakoff syndrome; FASD |
| Benzodiazepines and sedative-hypnotics | Alprazolam, lorazepam, clonazepam, diazepam; zolpidem; barbiturates; GHB | Sedation, slurred speech, ataxia, memory impairment (anterograde amnesia), disinhibition | Anxiety, insomnia, tremor, autonomic hyperactivity, perceptual disturbances, seizures, delirium | Fatal withdrawal; overdose with opioids or alcohol; GHB has a narrow safety margin |
| Opioids | Heroin, fentanyl and analogs, oxycodone, hydrocodone, morphine, methadone | Euphoria then apathy, drowsiness ("nodding"), pinpoint pupils, slurred speech, slowed breathing | Dysphoria, muscle aches, lacrimation, rhinorrhea, dilated pupils, piloerection, sweating, yawning, nausea, vomiting, diarrhea, insomnia | Fatal overdose; fentanyl potency; xylazine adulterant (sedation not reversed by naloxone, severe wounds); HIV and hepatitis C |
| Stimulants | Cocaine (powder, crack), methamphetamine, prescription amphetamine and methylphenidate | Euphoria, energy, hypervigilance, rapid pulse, raised blood pressure, dilated pupils, agitation, paranoia | "Crash": dysphoric mood, fatigue, vivid unpleasant dreams, increased sleep and appetite, anhedonia | Heart attack, stroke, hyperthermia, seizures, psychosis; fentanyl contamination; suicidal ideation in the crash |
| Cannabis | Marijuana, concentrates (wax, dabs), edibles, vapes containing THC | Euphoria, slowed reaction time, impaired short-term memory, red eyes, increased appetite, dry mouth, anxiety or paranoia | Irritability, anxiety, sleep difficulty, decreased appetite, restlessness, depressed mood, physical discomfort | Psychosis (high-potency products, adolescent use); cannabinoid hyperemesis syndrome; impaired driving |
| Hallucinogens | LSD, psilocybin, mescaline; MDMA (also has stimulant properties) | Perceptual distortions, synesthesia, dilated pupils, anxiety or panic; MDMA: emotional closeness, jaw clenching | No recognized withdrawal syndrome for classic hallucinogens; MDMA may be followed by days of low mood and fatigue | Injury; hallucinogen persisting perception disorder; MDMA: hyperthermia, hyponatremia |
| Dissociatives | PCP, ketamine, high-dose dextromethorphan | Detachment, numbness, nystagmus (horizontal or vertical with PCP), ataxia, raised blood pressure, agitation or violence (especially PCP) | No well-established withdrawal syndrome in DSM-5-TR | Injury due to analgesia and agitation; psychosis; ketamine-related bladder damage |
| Inhalants | Solvents, glues, paint thinner, aerosols, nitrous oxide, nitrites | Dizziness, euphoria, slurred speech, incoordination, lethargy, chemical odor, rash or residue around nose and mouth | No DSM-5-TR withdrawal diagnosis | Sudden sniffing death (arrhythmia); brain, nerve, liver, and kidney damage; most common in younger adolescents |
| Nicotine / tobacco | Cigarettes, e-cigarettes and vapes, cigars, smokeless tobacco | Alertness, improved concentration, increased heart rate (no DSM intoxication diagnosis) | Irritability, anxiety, difficulty concentrating, increased appetite, restlessness, depressed mood, insomnia, craving | Smoking is the leading preventable cause of death (cancer, heart disease, COPD) |
Dangerous Withdrawal
Withdrawal from alcohol and benzodiazepines/sedative-hypnotics (including GHB) can cause seizures, delirium, and death. These clients need medical evaluation and supervised withdrawal management. Opioid withdrawal is rarely life-threatening; its main danger is return to use with lost tolerance.Recognizing and Responding to Overdose
Opioid Overdose Triad
- Pinpoint pupils (miosis)
- Respiratory depression — slow, shallow, or absent breathing; gurgling or snoring sounds
- Unconsciousness or unresponsiveness; bluish or gray lips and fingertips
1
Check responsiveness
Shout and apply a firm sternal rub.
2
Call 911
Good Samaritan laws in most states protect callers.
3
Give naloxone
Nasal spray or intramuscular injection; repeat every 2–3 minutes if no response.
4
Support breathing
Give rescue breaths if trained; otherwise place the person in the recovery position.
5
Stay and monitor
Naloxone can wear off before the opioid does, so overdose symptoms may return.
Naloxone Essentials
- Opioid antagonist that displaces opioids from mu receptors and reverses respiratory depression within minutes.
- No effect without opioids present and no misuse potential — safe to give when unsure.
- Does not reverse benzodiazepines, alcohol, stimulants, or xylazine — but give it anyway, because mixed-substance overdoses usually involve opioids.
- May precipitate acute withdrawal in an opioid-dependent person.
- Fentanyl overdoses may require more than one dose.
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