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

29 combo interactions documented

toxicity data (PsychonautWiki, PubChem)

Aliases: Demerol, Dolantin, Meperidine, Dolcontral

Summary dose.wiki TripSit PsychonautWiki

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 source varies by route

ROA	Light	Common	Strong	Heavy
Oral	50-100mg	100-200mg	200-400mg	400mg+
Intramuscular	25-50mg	-	-	-
Intravenous	25-50mg	-	-	100+ mg (extreme caution - rapid respiratory depression)
Subcutaneous	25-50mg	-	-	-

Light Common Strong Heavy

Sources· 1 of 4 ladders not fully identified

Oral

Dose ladder — dose.wiki, PsychonautWiki, TripSit

Intramuscular

Dose ladder — DrugsPRO

Intravenous

Dose ladder — Light: DrugsPRO · Heavy: not identified

Subcutaneous

Dose ladder — DrugsPRO

Onset, Duration & After-effects dose.wiki TripSit PsychonautWiki

ROA	Onset	Peak	Offset	After Effects	Total
Oral	30-60 min	1-2 hrs	2-4 hrs	2-10 hrs	4-6 hrs
Intramuscular	10-15 min	30-60 min	1-2 hrs	1-6 hrs	4-6 hrs
Intravenous	1-5 min	5-10 min	1-2 hrs	1-6 hrs	4-6 hrs
Subcutaneous	10-20 min	30-60 min	1-2 hrs	1-6 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.

Convert from

Convert to

100 mg Pethidine

≈

— mg Morphine

⚠ 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

10 reports

Scores (0–10) curated from multiple sources:

Effect keyword matching from PsychonautWiki catalog
Weighted by importance: core (×3), major (×2), minor (×1)

Full methodology

Opioid 7.6

Intense 8/10

Strong euphoria and pain relief with moderate itching/nausea, mild sedation

Euphoria / Warmth ×3

physical euphoria cognitive euphoria euphoria mood lift

Analgesia ×2

pain relief analgesia

Sedation / Relaxation ×1

sedation dream potentiation

⚠ Itching / Nausea ×1

nausea constipation dry mouth

Based on reports from:

Erowid Experience Reports

Tolerance

Build-up develops within days of regular use; analgesic tolerance faster than respiratory depression tolerance

Reset Falls quickly once you stop, at a rate you can't judge. After any break, treat your tolerance as gone.

No tolerance chart. Our decay curves for opioids were estimates, and a curve can make tolerance look longer-lasting than it is, which is the dangerous direction.

Opioid tolerance drops fast when you stop, and even a few days off can be enough, so a dose that used to be normal can now stop your breathing. Overdose deaths rise sharply after prison, detox or leaving treatment, and tolerance also falls during a hospital stay. After any break, start with a much smaller amount, try a test dose first, don't use alone, and keep naloxone within reach. Alcohol, benzodiazepines, gabapentinoids and other sedatives make an opioid overdose much more likely.

Sources: FRANK: heroin · National Harm Reduction Coalition · WHO: opioid overdose · Merrall et al. 2010 · Binswanger et al. 2007 · Strang et al. 2003 · FDA 2019: gabapentinoids and breathing

Effects Erowid

Aggregated from 10 single-substance Erowid experience reports; 9 Erowid reports where another drug was taken too are left out

Each bar shows the share of analyzed reports whose text mentions that effect — a mention is not always a first-hand experience (fear of an effect or something witnessed can count). Mentions saying the effect did not happen are left out; that check reads keywords, so it can miss some. The shaded band on a bar, and the small range after its number, is the 95% interval: where the share could plausibly be with other reports of the same kind. Fewer reports, wider band. Tap or hover any number for details. The second value is the Bluelight extractor's per-effect confidence; a dash means the row is Erowid-derived, which has no confidence measurement.

Too few reports for bars: these effects come from 10 single-substance Erowid reports, and a bar is drawn only from 20 reports or more. With fewer, a percentage cannot tell a common effect from a rare one. Counts are shown instead. Why 20?

Positive Effects 4

3 of 10 –

Adverse Effects 1

3 of 10 –

Also reported in combinations. In the 9 Pethidine reports where another drug was taken too, 3 mention hospital, emergency services or an overdose, 0 a seizure and 0 psychosis (too few reports for percentages). In the 10 single-substance reports: 5, 2 and 0. These are not in the figures above: they cannot be put down to Pethidine alone, and a mention is not always something that happened to the writer.

Combinations TripSit

Cross-Check Pethidine with another substance

These are TripSit's opioid interactions, except the MAOI entry: TripSit rates opioids with MAOIs as Caution, but pethidine is the opioid the MAOI labels single out, so it is Dangerous here.

Community Trip Reports

Anecdotal first-person accounts from Reddit, Erowid, Bluelight, and Dose.wiki. Click a source to expand. Reports are harm-reduction context, not medical guidance. Tags summarise each author's own verdict — how reports are classified.

Erowid 8 reports 1 positive 3 neutral 4 cautionary visit

Mildly Pleasant on Pure Meperidine neutral exp #83610

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.

Safety First cautionary exp #30339

[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.

An Overall Medicore Experience neutral exp #67423

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...

Effects of a Non-fatal Overdose cautionary exp #78578

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.

Worked Fine cautionary exp #25503

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.

I Was Able to Stay Awake and Enjoy the Full Ride positive exp #113140

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).

Vein honey cautionary exp #22430

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.

Snorting Meperidine, Take 2: Pain v. Pleasure neutral exp #83693

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

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Pethidine's nerd page Pharmacology, chemical data, effect profiles, and more

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Helpful Links

💊 Pill Identifier 📘 Experience Reports 📖 dose.wiki 📖 TripSit 📖 PsychonautWiki

Add missing routes to PsychonautWiki Journal

The PsychonautWiki Journal app already has Pethidine, but its built-in entry only covers Oral. Here are the other routes we have data for. You can't edit a built-in substance, but you can add a Custom Unit for any of these routes to log it.

⬇ Download import file Import this file as custom substances and you get "Pethidine (Substance Search)" with every route's full dose ladder and timeline, no typing. Works on iOS and Android (v15+); the format is confirmed by the app's developer. The manual values below work for older versions.

Dose & duration (reference)

Pethidine: routes the PsychonautWiki Journal app is missing
Source: SubstanceSearch (substancesearch.com)

Intramuscular dose (mg): light 25-50
Intravenous dose (mg): light 25-50 · heavy 100+  (extreme caution - rapid respiratory depression)
Subcutaneous dose (mg): light 25-50

Intramuscular duration: onset 10-15m · peak 0.5-1h · offset 1-2h · total 4-6h · after-effects 1-6h
Intravenous duration: onset 1-5m · peak 5-10m · offset 1-2h · total 4-6h · after-effects 1-6h
Subcutaneous duration: onset 10-20m · peak 0.5-1h · offset 1-2h · total 4-6h · after-effects 1-6h

Note: ranges are harm-reduction guidance, not a prescription. Start low, go slow, and test your substances.

Ranges are harm-reduction guidance, not a prescription.

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.

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 29 combo interactions documented toxicity data (PsychonautWiki, PubChem)