Heroin produces 25 documented subjective effects across 2 categories.
Full Heroin profileThe experience of heroin begins within seconds of intravenous injection, or within ten to fifteen minutes if smoked or insufflated. The onset arrives as a sudden, powerful wave of warmth that radiates outward from the chest and abdomen, flooding the entire body in a sensation often described as being wrapped in a thick blanket of liquid heat. This initial rush is intensely pleasurable, carrying a depth of physical satisfaction that eclipses all ordinary feelings of comfort. The muscles unclench entirely, and every source of tension or pain in the body seems to dissolve at once.
Within minutes the rush settles into a sustained state of profound tranquility. The mind enters a condition of extraordinary contentment in which worries, anxieties, and emotional pain feel impossibly distant, as though they belong to another person entirely. There is no euphoria in the manic or energetic sense; rather, it is a deep stillness, a feeling that everything is exactly as it should be and that nothing in the world requires attention or effort. Thought processes slow to a gentle drift, and the usual internal monologue quiets to a murmur. The eyelids grow heavy and the pupils constrict to pinpoints.
Physically, the body enters a state of near-total relaxation. Breathing slows and becomes shallow, the heart rate decreases, and the skin may flush warm and dry. Itching is common, particularly around the nose and face, caused by histamine release. Nausea can occur, especially in opioid-naive individuals, sometimes leading to vomiting, though even this is often experienced with unusual indifference. The phenomenon of "nodding" frequently develops: a drowsy oscillation between wakefulness and a dreamlike half-sleep in which the head dips forward and consciousness fades in and out.
The experience typically lasts three to five hours, during which hunger, thirst, and sexual drive are suppressed. The comedown is not abrupt but rather a slow ebbing of the warmth and contentment, leaving behind a flat, somewhat foggy mental state. With repeated use the body adapts rapidly, and the same dose produces progressively less effect, driving the dose escalation and compulsive redosing patterns that define opioid dependence. The contrast between the profound relief of intoxication and the growing discomfort of withdrawal becomes the central architecture of addiction.
A distinct decrease in hunger and desire to eat, ranging from reduced interest in food to complete disinterest or even physical revulsion at the thought of eating. This effect can persist for many hours beyond the primary experience.
ConstipationA slowing or cessation of bowel movements resulting in difficulty passing stool, commonly caused by opioid receptor activation in the gastrointestinal tract and notoriously resistant to tolerance development.
DiarrheaDiarrhea is the occurrence of frequent, loose, or watery bowel movements as a side effect of certain psychoactive substances, resulting from either direct GI irritation or pharmacological alterations to gut motility and fluid absorption.
Difficulty urinatingDifficulty urinating, also known as urinary retention, is the experience of being unable to easily pass urine despite a full bladder, commonly caused by stimulant, opioid, and anticholinergic substances that affect bladder muscle control.
Dry mouthA persistent, uncomfortable reduction in saliva production causing the mouth and throat to feel parched, sticky, and difficult to swallow through, commonly known as cottonmouth.
HeadacheA painful sensation of pressure, throbbing, or aching in the head that can range from a dull background discomfort to a debilitating pounding that dominates awareness. Substance-induced headaches may occur during the acute effects, during the comedown, or as a rebound symptom hours to days after use.
Increased heart rateA noticeable acceleration of heartbeat that can range from a subtle awareness of one's pulse to a forceful, rapid pounding felt throughout the chest, neck, and temples. This effect is among the most commonly reported physiological responses to psychoactive substances and often accompanies stimulation, anxiety, or physical exertion during intoxication.
InsomniaA persistent inability to fall asleep or maintain sleep despite physical tiredness, often characterized by a racing mind, heightened alertness, and a frustrating disconnect between bodily fatigue and mental wakefulness. This effect can persist for hours beyond the primary duration of a substance, significantly extending the total experience timeline.
Motor control lossA distinct decrease in the ability to control one's physical body with precision, balance, and coordination, ranging from minor clumsiness to complete inability to walk.
NauseaAn uncomfortable sensation of queasiness and stomach discomfort that may or may not lead to vomiting, often occurring during the onset phase of many substances.
Pain reliefA suppression of negative physical sensations such as aches and pains, ranging from dulled awareness of discomfort to complete inability to perceive pain.
Physical euphoriaAn intensely pleasurable bodily sensation that can manifest as waves of warmth, tingling electricity, or a full-body orgasmic glow radiating outward from the core. This effect is often described as one of the most rewarding physical sensations available through psychoactive substances and is a primary driver of the recreational appeal of many substance classes.
Pupil constrictionA visible narrowing of the pupil diameter (miosis) that reduces the size of the dark center of the eye to a small pinpoint. This effect is one of the most reliable physical indicators of opioid intoxication and is often the first sign noticed by medical professionals and observers when assessing someone under the influence of opioids or certain other substance classes.
Respiratory depressionA dangerous slowing and shallowing of breathing that can progress from barely noticeable reductions in respiratory rate to life-threatening cessation of breathing. This is the primary mechanism of death in opioid overdoses and represents one of the most critical safety concerns across all of psychopharmacology.
SedationA state of deep physical and mental calming that manifests as a progressive desire to remain still, lie down, and eventually drift toward sleep. Sedation ranges from a gentle drowsy relaxation to a heavy, irresistible pull into unconsciousness where maintaining wakefulness becomes a losing battle against the body's insistence on shutdown.
SeizureUncontrolled brain electrical activity causing convulsions and loss of consciousness -- a life-threatening medical emergency requiring immediate help.
Spontaneous physical movementsSpontaneous physical movements are involuntary, seemingly random yet patterned body movements — twitches, swaying, gestures, or full-body undulations — that appear to arise from and correspond to the individual's internal cognitive and sensory experience rather than from conscious motor commands.
TinnitusPhantom perception of ringing, buzzing, or hissing in the ears without external sound source, potentially caused or worsened by certain substances.
A complete or partial inability to form new memories or recall existing ones during and after substance use, ranging from minor gaps in recollection to total blackouts encompassing hours of experience.
AnxietyIntense feelings of apprehension, worry, and dread that can range from a subtle background unease to overwhelming panic attacks with a sense of impending doom, often amplified by the substance's intensification of one's existing mental state.
Anxiety suppressionA partial to complete suppression of anxiety and general unease, producing a calm, relaxed mental state free from worry. This can range from subtle tension relief to a profound sense of inner peace and emotional security.
Cognitive euphoriaA cognitive and emotional state of intense well-being, elation, happiness, and joy that manifests as a profound mental contentment and positive outlook. This ranges from gentle feelings of optimism and warmth to overwhelming bliss that pervades all thoughts and perceptions.
Compulsive redosingAn overwhelming, difficult-to-resist urge to continuously take more of a substance in order to maintain or intensify its effects, often overriding rational judgment and self-control.
DepressionA persistent state of low mood, emotional numbness, hopelessness, and diminished interest or pleasure in activities, often occurring during comedowns, withdrawal, or as a prolonged after-effect of substance use.
WakefulnessAn increased ability to stay awake and alert without the desire to sleep. Distinct from stimulation in that it does not elevate energy above a naturally rested baseline.
Heroin can produce 18 physical effects including sedation, pain relief, nausea, pupil constriction, and 14 more.
Heroin produces 7 cognitive effects including anxiety suppression, cognitive euphoria, compulsive redosing, wakefulness, and 3 more.