Antihistamine Effects

A 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.

A 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.

A 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.

Uncontrolled brain electrical activity causing convulsions and loss of consciousness -- a life-threatening medical emergency requiring immediate help.

A 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.

An 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.