Set: At ease. I am a well-experienced user (spent many years on codeine and huge doses of tramadol, have experimented with many other opiates and opioids). Not currently addicted, though I do take various opiates and opioids on occasion.
Pethidine
Well-documented
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 19 combo interactions documented
- PubChem toxicity data
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 19 combo interactions documented
- PubChem toxicity data
Aliases: Demerol, Dolantin, Meperidine, Dolcontral
Summary
Pethidine is significantly less safe than other opioids due to its toxic metabolite norpethidine, which accumulates with repeated dosing and can cause seizures, tremors, and CNS excitation. It should not be used for more than 48 hours or at doses exceeding 600 mg per 24 hours. The drug has a particularly high risk of serotonin syndrome compared to other opioids and should never be combined with MAOIs, SSRIs, or other serotonergic drugs.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 50-100mg | 100-200mg | 200-400mg | 400mg+ |
| Intramuscular | 25-50mg | - | - | - |
| Intravenous | 25-50mg | - | - | 100+mg(extremecaution-rapidrespiratorydepression) |
| Subcutaneous | 25-50mg | - | - | - |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Peak | Offset | Total |
|---|---|---|---|---|
| Oral | 30-60 min | 1-2 hrs | 2-4 hrs | 4-6 hrs |
| Intramuscular | 10-15 min | 30-60 min | 1-2 hrs | 4-6 hrs |
| Intravenous | 1-5 min | 5-10 min | 1-2 hrs | 4-6 hrs |
| Subcutaneous | 10-20 min | 30-60 min | 1-2 hrs | 4-6 hrs |
Opioid MME Calculator
⚠ Citation & Disclaimer:
Conversion factors sourced from the
NIH HEAL Initiative MME Calculator (Adams et al., PAIN 2025),
the CDC 2022 Clinical Practice Guideline for Prescribing Opioids for Pain,
and the MDCalc MME Calculator.
These are approximate equianalgesic ratios for educational reference only.
Individual responses vary significantly based on genetics, tolerance, cross-tolerance, and route of administration.
This is not medical advice. Do not use these conversions to adjust opioid dosing without professional medical guidance.
mg
100
mg
Pethidine
≈
—
mg
Morphine
| Substance | Equivalent Dose | MME Factor |
|---|
⚠ Equianalgesic dose ratios are approximations and do not account for genetic factors, tolerance, incomplete cross-tolerance, or pharmacokinetic variations. Methadone conversion is especially variable at higher doses. Always consult a healthcare provider before making any changes to opioid therapy.
Effect Profile
19 reportsScores (1–10) curated from multiple sources:
- Effect keyword matching from PsychonautWiki catalog
- Weighted by importance: core (×3), major (×2), minor (×1)
Opioid
7.6
Intense
8/10
Strong euphoria and pain relief with moderate itching/nausea, mild sedation
Euphoria / Warmth
×3
10
physical euphoria
cognitive euphoria
euphoria
mood lift
Analgesia
×2
8
pain relief
analgesia
Sedation / Relaxation
×1
4
sedation
dream potentiation
Itching / Nausea
×1
7
nausea
constipation
dry mouth
Based on reports from:
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
Acute tolerance: develops within a single session — the reset numbers above apply after sustained heavy use, not after one binge. Within-session tachyphylaxis usually resets largely overnight.
Effects
Aggregated from 19 Erowid experience reports
Positive Effects 8
Euphoria
31.6%
70%
Tactile Enhancement
26.3%
70%
Sedation
26.3%
70%
Stimulation
26.3%
70%
Empathy
21.1%
70%
Music Enhancement
21.1%
70%
Pain Relief
15.8%
70%
Focus Enhancement
15.8%
70%
Adverse Effects 3
Nausea
31.6%
70%
Headache
21.1%
70%
Confusion
21.1%
70%
Combinations
Cross-Check Pethidine with another substanceCommunity Trip Reports
Anecdotal first-person accounts from Reddit, Erowid, and Bluelight. Click a source to expand. Reports are harm-reduction context, not medical guidance.
Erowid 8 reports 3 neutral 5 cautionary visit
[Erowid Note: The dose described in this report is very high, potentially beyond Erowid's 'heavy' range, and could pose serious health risks or result in unwanted, extreme effects. Sometimes extremely high doses reported are errors rather than actual doses used.] I would consider myself an experienced opiate user.
As with all the reports I write, I'll provide some personal background. I'm a 145 lb, very athletic male, 21 years old. I'm a very experienced drug user, and prior use includes MJ, benzos (xanax, valium), mushrooms in low and very high doses, amphetamines (oral and IV), and opioids/opiates (oral, subcutaneous, and IV o...
After an extremely significant (bad) experience (non-fatal overdose) with Demerol (Meperidine), Im compelled to tell my story to those who may be in a position to take a very high dose of it, at least in its injectable form, which is all I can really comment on.
I drove myself to an emergency room with an extremely painful kidney stone. The stone turned out to be small - about 5mm. In fact, it was so small that I was a bit taken by surprise when it finally came out. Nevertheless, it hurt intensely while it was in my ureter. The pain was so intense I felt like throwing up.
Best Opiate High I've Ever Had This is not my first time using opiate substances. I take them on the rare occasion when I happen to run across some. T-7am I had been saving these two pills for the perfect time to take them (when I had nothing important to do).
I was riding my motorcycle at about 10 pm, down a main street in Venice Beach, CA, when a car shot through an intersection. I only saw bright lights for a split second before I hit the car head-on. I initially hit the pavement with my head and shoulder--my helmet undoubtedly saved my life.
Mindset: This was to be my second try insufflating meperidine. I am a well-experienced user, though not currently addicted. Setting: My condominium one weekday evening, February 3, 2010 Drug: Meperidine HCl, USP reference standard (as close as one gets to 100% pure) Experience: Administration: Insufflated ~75 mg.
Pill Identifiers
12
known pill identifiers on record — view imprints, colors, shapes, and images
→
Pethidine's nerd page
Pharmacology, chemical data, effect profiles, and more
→
Helpful Links
Report an issue or suggest an edit
Spotted incorrect or dangerous information, have a correction, a new study, or a useful addition for Pethidine? Let us know. Reports are reviewed by moderators — this is not posted publicly.