Most potent opioids


Don't buy from me
Feb 2, 2024
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This table is from wiki Equianalgesic page. It is a bit inaccurate and far from being complete list, but I'll later add more interesting compounds.


This chart measures pain relief versus mass of medication. Not all medications have a fixed relationship on this scale. Methadone is different from most opioids because its potency can vary depending on how long it is taken. Acute use (1–3 days) yields a potency about 1.5× stronger than that of morphine and chronic use (7 days+) yields a potency about 2.5 to 5× that of morphine. Similarly, the effect of tramadol increases after consecutive dosing due to the accumulation of its active metabolite and an increase of the oral bioavailability in chronic use.

Comparison to oral morphine

Equivalent dose
(10 mg oral morphine)
Paracetamol (non-opioid)1⁄3603600 mg63–89%1–437 min (PO); 8 min (IV)5–6 hours
Aspirin (NSAID, non-opioid)1⁄3603600 mg80–100%3.1–9
Ibuprofen[10] (NSAID, non-opioid)1⁄2222220 mg87–100%1.3–3
Diflunisal (NSAID, non-opioid)1⁄1601600 mg80–90%8–12
Naproxen[10] (NSAID, non-opioid)1⁄1381380 mg95%12–24
Piroxicam (NSAID non-opioid)1⁄120 (est.)
Indomethacin (NSAID non-opioid)1⁄64 (est.)
Diclofenac[10][11] (NSAID, non-opioid)1⁄10 (est.) (same as Codeine)100 mg (est.)50–60%1–4
Ketorolac[12] (NSAID, non-opioid)1⁄3 (est.)30 mg IV (est.)80–100%5–7
Nefopam (Centrally-acting non-opioid)5⁄8 (est.)16 mg IM (est.)Nefopam: 3–8, Desmethylnefopam 10–15
Dextropropoxyphene[13]1⁄13–1⁄20130–200 mg
Codeine1⁄10–3⁄20100–120 mg (PO)~90%2.5–3 (C6G 1.94;[14] morphine 2–3)15–30 min (PO)4–6 hours
Tramadol1⁄10~100 mg75% (IR), 85–90% (ER)6.0–8.8[15] (M1)
Opium (oral)1⁄10~100 mg~25% (morphine)2.5–3.0 (morphine, codeine)
Tilidine1⁄10100 mg
Dihydrocodeine1⁄550 mg20%4
Anileridine[16]1⁄440 mg
Alphaprodine1⁄4–1⁄640–60 mg
Tapentadol[17]3⁄1032 mg32% (fasting)
Pethidine (meperidine)1⁄330 mg SC/IM/IV, 300 mg (PO)50–60%3–5
Hydrocodone110 mg70%[18]3.8–6 (Instant Release; PO)10–30 min (Instant Release; PO)4–6
Metopon110 mg
Pentazocine lactate (IV)[19]110 mg SC/IV/IM, 150 mg (PO)
Morphine (oral) 1 10 mg ~25%2–43:130 min (PO)3–6 hours
Oxycodone (oral)[20]1.56.67 mg60-87%2–3 hours (Instant Release)(PO); 4.5 hours (Controlled Release)(PO)10–30 min (Instant Release)(PO); 1 hour (Controlled Release)(PO)3–6 hours (Instant Release)(PO); 10–12 hours (Controlled Release)(PO)[21]
Nicomorphine2–33.33–5 mg20%4
Oxycodone (IV)[22]33.33 mg96%1.5–3 (IV)5 min (IV)[22]2-4 hours
Morphine (IV/IM)33.33 mg100%2–33:1Instantaneously (from 5 to 15 sec; IV); 5–15 min (IM)3–7 hours
Clonitazene33.33 mg
Methadone (acute)[23][24]3–42.5–3.33 mg40–90%15–602:1
Methadone (chronic)[24]2.5–52–4 mg40–90%15–602:1
Phenazocine4~2.5 mg
Diamorphine (Heroin; IV/IM)[25]4–5 (iv, im) 2–2.5 (insufflated)[26]2–2.5 mg100%<0.6 (morphine prodrug)[27]Instantaneously (from 5 to 15 sec; IV); 2 to 5 min (IM)3 to 7 hours
Dezocine4–61.6–2.5 mg97% (IM)2.2
Hydromorphone[28][29][17]10 (SC, IV, IM)
3–3.75 (PO)
0.5-0.75 mg (SC, IV, IM)
2.5 mg (PO)
Orally: 30–35%, Intranasal:
52- 58% IV/IM: 100% 62%
Oxymorphone[20]10 (SC, IV, IM)
3.33 mg (PO), 0.333 mg (IV,IM & Interlaminar)PO: 10%
Buccal: 28% Sublingual:37.5% Intranasal: 43% IV, IM & IT: 100%
7.25–9.4335 min (PO), Instantaneously (from 5 to 15 sec)(IV)6–8 hours orally
2-6 hours parenteral
U-477007.51.5 mg1.5–3
Levorphanol[30]81.25 mg70%11–161:1
Desomorphine (Krokodil)8–101–1.25 mg~100% (IV)2–3Instantaneously (from 5 to 15 sec)(IV); 2–5 min (IM)3–4 hours
Alfentanyl10–251.5 (90–111 minutes)Instantaneously (from 5 to 15 sec); 4× more rapid than fentanyl0.25 hr (15 min); up to 54 minutes until offset of effects
7-Hydroxymitragynine17~0.6 mg
Enadoline2515 μg (threshold) and 0.160 mg/kg (dissociative effects)
Buprenorphine (SL)[13]400.25 mg30% (SL);[31] ~100% (TD); 65% (buccal);[32][33] 48% (INS)[34]20–70, mean 373:145 min12–24 hours
N-Phenethyl-14-ethoxymetopon60160 μg
Phenomorphan60–800.13–0.16 mg
Fentanyl50–1000.1 mg (100 μg) IM/IV33% (SL); 92% (TD); 89% (INS); 50% (buc)0.04 (IV); 7 (TD)5 min (TD/IV)30–60 minutes (IV)
Metonitazene1000.1 mg/100 μg
Buprenorphine (Transdermal)[35][36]100–1150.1 mg (100 μg)30% (SL);[31] ~100% (TD); 65% (buccal);[32][33] 48% (INS)[34]3:145–60 minutes12–24 hours
14-Cinnamoyloxycodeinone17777 μg
Etonitazepyne180-19055-60 μg
Protonitazepyne180-19055-60 μg
Remifentanil100–20050–100 μg0.05 (3–6 min context-sensitive half-life; 7–18min elimination half-life)Instantaneously (from 5 to 15 sec)15 minutes; rapid offset of effects necessitates continuous infusion for maintenance of anesthesia
Protonitazene20050 μg
Ocfentanil125–25040–80 μg
Ro4-1539240–48020-40 μg
Isotonitazene50020 μg
Sufentanil500–1,00010–20 μg4.4
BDPC504~20 μg
Etonitazene1000-15006,6-10 μg
N-Desetylisotonitazene1000-20005-10 μg
Etorphine1,000-3,0003.3–10 μg
Acetorphine87001.33 μg
Dihydroetorphine[37]1,000–12,0000.83–10 μg (20–40 μg SL)
Carfentanil[38]10,0001.0 μg7.7
14-Methoxymetopon (intraspinally)[39](1,000,000)

PO: oral • IV: intravenous injection • IM: intramuscular injection • SC: subcutaneous injection • SL: sublingual • TD: transdermal
"Strength" is defined as analgesic potency relative to oral morphine.
Tolerance, sensitization, cross-tolerance, metabolism, and hyperalgesia may be complex factors in some individuals.
Interactions with other drugs, food and drink, and other factors may increase or decrease the effect of certain analgesics and alter their half-life.
Because some listed analgesics are prodrugs or have active metabolites, individual variation in liver enzymes (e.g., CYP2D6 enzyme) may result in significantly altered effects.

You should note that this is combined data from different methods of measuring potency on different animals, especially for the most potent ones. So carefully translate this data for the human potency.
For example, Ohmefentanyl potency here is listed as 6300, but it has 8 isomers, one of it - (3R,4S,βS) is considerably stronger than others, or around 6300 stronger than morphine for mouses, BUT for monkeys it is EXTREMELY potent, up to 50.000 times or even more compared to morphine (it was very hard to measure precisely), so more likely it will be similar case for humans. This makes it one of the most potent compounds EVER, not only as pain killers, but also as plain killers, pushing such classical warfare nerve agents as VX out of the game.
Another case is comparison of carfentanil and lofentanil (carfentanil with 3-Methyl group on piperidine ring), later is listed here as 10k-100k potency, but in animal studies is about twice less potent than carfentanil, the opposite case is for humans - it is more potent, and many times more toxic, because it lasts up to 3 days.
There are already compounds with potency rate up to million times compared to morphine (not only by instraspinally route) and likely later appear even more ones, as a result of success in AI prediction of protein folding and binding, but I don't want to list it here, as working with such materials is disaster.
Those who continue the war with amateur and clandestine chemistry should clearly understand that with their actions they only push people to work with more and more potent substances, because year by year it become harder and harder to order chemicals in necessary quantities.
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