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    Disclaimer
    🧪 This is a research chemical with limited data on its long-term health effects, toxicity profile, and safe dosage ranges.
    ⚠ Opioids carry significant risk of respiratory depression, physical dependence, and fatal overdose. Never combine with other depressants.

    U-49900 Limited data
    Limited data
    Sparse data. Doses and effects may be unreliable or untested.
    • 2 corroborating sources
    • no dose data
    • 19 combo interactions documented
    • classified Tentative
    • classified Research-chemical

    Depressant Research-chemical Opioid

    Summary TripSit

    A synthetic opioid sold as an analogue of U-47700, though it shares little of its profile. TripSit staff have pointed readers to a user write-up of an unpleasant and unpredictable experience with it: https://www.reddit.com/r/researchchemicals/comments/5gbo3e/u49900_experiment_and_warning/. No dose data is established.

    Effect Profile

    class estimate

    Scores (1–10) curated from multiple sources:

    • Effect keyword matching from PsychonautWiki catalog
    • No reports exist for this substance. Its effect list is the one shared by 2 other substances of the same class, so the scores below describe the class, not this compound.
    • Weighted by importance: core (×3), major (×2), minor (×1)

    Full methodology

    Opioid 3.9
    Moderate 4/10

    Moderate euphoria with mild itching/nausea, low sedation

    Euphoria / Warmth ×3
    6
    euphoria cognitive euphoria
    Analgesia ×2
    0
    Sedation / Relaxation ×1
    3
    sedation
    ⚠ Itching / Nausea ×1
    4
    nausea
    View methodology →

    Tolerance

    Build-up develops within days of regular use; analgesic tolerance faster than respiratory depression tolerance
    Reset 7–14 days for partial reset; full reset may take weeks — tolerance loss greatly increases overdose risk

    Tolerance Decay

    Full tolerance 1d Half tolerance 21d Baseline ~35d

    Effects

    Positive
    • Stimulation
    Negative
    • Motor impairment
    • Increased heart rate
    • Nausea
    • Insomnia
    • Vasoconstriction
    • Restlessness
    Neutral
    • Sedation
    • Decreased appetite
    Positive
    • Reduced anxiety
    • Euphoria
    • Cognitive euphoria
    • Wakefulness
    • Empathy
    Negative
    • Anxiety
    • Confusion
    • Compulsive redosing
    Neutral
    • Time distortion
    • Talkativeness
    Positive
    • Increased music appreciation
    • Color enhancement
    • Tactile enhancement
    • Brightened colour
    Negative
    • Light sensitivity
    • Appetite suppression
    • Dehydration
    • Disinhibition
    Neutral
    • Dulled perception
    • Drifting

    Combinations TripSit

    Cross-Check U-49900 with another substance

    U-49900's nerd page Pharmacology, chemical data, effect profiles, and more
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    Helpful Links

    📘 Experience Reports 📖 TripSit 📖 PsychonautWiki