Pethidine Stats & Data

Measured binding and functional data for pethidine, curated by the IUPHAR/BPS Guide to PHARMACOLOGY. Each row cites the paper it came from. Lower concentrations mean tighter binding — a value in the sub-nanomolar range indicates a very potent interaction.

Reading this. pKi, pEC50 and pIC50 are negative log molar values, so a higher number means a tighter interaction; the concentration column converts them for you. Values from non-human species are laboratory measurements and do not translate directly to human effect. Receptor affinity is not a dose — it describes what a molecule binds, not how much of it is safe to take.

Receptor data from the IUPHAR/BPS Guide to PHARMACOLOGY (v2026.2), licensed CC BY-SA 4.0. Matched to this substance by InChIKey.

Pethidine has a high toxicity relative to dose. As with all opioids, long-term effects can vary but can include diminished libido, apathy and memory loss. It is also potentially lethal when mixed with depressants like alcohol or benzodiazepines and generally has a wider range of substances which it is dangerous to combine with in comparison to other opioids. One of pethdine's metabolites, norpethidine has little to no opioid action, but is known to cause seizures. Pethidine should not be taken during benzodiazepine withdrawals as this can potentially cause seizures.

Effects aggregated from 10 experience reports (10 single-substance Erowid)

Each bar is the share of reports mentioning the effect; its whisker, and the band on the rows below, is the 95% interval: where the share could plausibly be with other reports of the same kind.

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?

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.

From 17 of 29 recorded dose entries: those that state a weight (mg, g or µg), in routes with at least five of them. Values above Q3 + 3×IQR, far above what people typically take, are left out; they can include real heavy doses and overdoses, not only mistakes.

Most co-occurring substances, as a share of all 19 reports filed under Pethidine

Too few reports for bars: these combinations come from 19 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?

• Promethazine 4 of 19

Most common forms and preparations, as a share of the 14 reports that give one

Too few reports for bars: these forms come from 14 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?

• Liquid 6 of 14
• Pill / Tablet 5 of 14
• Ground / Crushed 2 of 14

Dose per kg of body weight, one dose per report (the first listed), from reports giving a weight of 30–250 kg. Doses above Q3 + 3×IQR, far above what people typically take, are left out of the median and range and listed under each route.

Redosing behavior across 14 reports