An equianalgesic chart is a conversion chart that lists equivalent doses of analgesics (drugs used to relieve pain). Equianalgesic charts are used for calculation of an equivalent dose (a dose which would offer an equal amount of analgesia) between different analgesics. Tables of this general type are also available for NSAIDs, benzodiazepines, depressants, stimulants, anticholinergics and others.

When using oral morphine as a baseline, the comparison of strengths of opioid analgesics is referred to as oral morphine equivalent.

Format Equianalgesic tables are available in different formats, such as pocket-sized cards for ease of reference. A frequently-seen format has the drug names in the left column, the route of administration in the center columns and any notes in the right column.

Purpose There are several reasons for switching a patient to a different pain medication. These include practical considerations such as lower cost or unavailability of a drug at the patient's preferred pharmacy, or medical reasons such as lack of effectiveness of the current drug or to minimize adverse effects. Some patients request to be switched to a different narcotic due to stigma associated with a particular drug (e.g. a patient refusing methadone due to its association with opioid addiction treatment). Equianalgesic charts are also used when calculating an equivalent dosage of the same drug, but with a different route of administration.

Precautions An equianalgesic chart can be a useful tool, but the user must take care to correct for all relevant variables such as route of administration, cross tolerance, half-life and the bioavailability of a drug. For example, the narcotic levorphanol is 4–8 times stronger than morphine, but also has a much longer half-life. Simply switching the patient from 40 mg of morphine to 10 mg of levorphanol would be dangerous due to dose accumulation, and hence frequency of administration should also be taken into account.

There are other concerns about equianalgesic charts. Many charts derive their data from studies conducted on opioid-naive patients. Patients with chronic (rather than acute) pain may respond to analgesia differently. Repeated administration of a medication is also different from single dosing, as many drugs have active metabolites that can build up in the body. Patient variables such as sex, age, and organ function may also influence the effect of the drug on the system. These variables are rarely included in equianalgesic charts.

Opioid equivalency table Opioids are a class of compounds that elicit analgesic (pain killing) effects in humans and animals by binding to the μ-opioid receptor within the central nervous system. The following table lists opioid and non-opioid analgesic drugs and their relative potencies. Values for the potencies represent opioids taken orally unless another route of administration is provided. As such, their bioavailabilities differ, and they may be more potent when taken intravenously.

Nonlinearities 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. This is called a dose-dependent potency curve and makes methadone somewhat unique among opioids, thought to be caused by the NMDA receptor activity of the drug then altering the behaviour of the opioid receptors that other opioids might target. 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 Analgesic Strength(relative) Equivalent dose(10 mg oral morphine) Bioavailability Half-life of active metabolites(hours) Oral-to-parenteral ratio Speed of onset DurationParacetamol (non-opioid)3600 mg63–89%1–437 min (PO); 8 min (IV)5–6 hours Aspirin (NSAID, non-opioid) 3600 mg 80–100% 3.1–9 Ibuprofen (NSAID, non-opioid) 2220 mg 87–100% 1.3–3 Diflunisal (NSAID, non-opioid) 1600 mg 80–90% 8–12 Naproxen (NSAID, non-opioid) 1380 mg 95% 12–24 Indomethacin (NSAID non-opioid) Diclofenac (NSAID, non-opioid) 100 mg (est.) 50–60% 1–4KetorolacPharma Guide Pre-Work 3rd Edition (NSAID, non-opioid)30 mg IM (est.)80–100%5–7 Nefopam (Centrally-acting non-opioid) 16 mg IM (est.) Nefopam: 3–8, Desmethylnefopam 10–15 Piroxicam (NSAID non-opioid)36.66 mg2–4 hours40 hours Dextropropoxyphene 130–200 mg Codeine 100–120 mg (PO) ~90% 2.5–3 (C6G 1.94; morphine 2–3)15–30 min (PO)4–6 hours Tramadol ~100 mg 75% (IR), 85–90% (ER) 6.0–8.8 (M1) Opium (oral) ~100 mg ~25% (morphine) 2.5–3.0 (morphine, codeine) Tilidine 100 mg 6% (parent drug), 99% (active metabolite) nortilidine 3.3 (PO) & 4.9 IV, bisnortilidine 5 (PO) & 6.9 (IV) 2.2:1 10–15 minutes (oral) 25–50 minutes (peak analgesic effect) 3–4 hours Dihydrocodeine 100 mg 20% 4 Anileridine 40 mg Alphaprodine 40–60 mg Tapentadol 32 mg 32% (fasting) Pethidine (meperidine) 30 mg SC/IV/IM 300 mg (PO) 50–60% Orally, 100% SC/IV/IM 3–55–15 sec if IV, 15–25 min if orallyDipipanone25 mg (PO)3.2–3.8 hours ±4 hoursBenzylfentanylAH-7921 SR-17018 10–12 mg 100% IV (Presumably) Unknown (researches are still being made) 5–10 seconds if used IV and 15–25 min orally (PO) Nalbuphine 10–11 mg ~33% (PO), 76% (SC), 81% (IM) 3–6 3 minutes, 10 minutes (peak effect) 3–6 hours Hydrocodone 1 10 mg 70% 3.8–6 (Instant Release; PO)10–30 min (Instant Release; PO)4–6 Pentazocine lactate (IV) 1 10 mg SC/IV/IM, 150 mg (PO) Morphine (oral) 1 10 mg ~25% 2–43:130 min (PO)3–6 hours Oxycodone (oral) 1.5 6.67 mg (60–87 / ±75% PO) / 78.2% (IN) / 100% (IV/IM) or other parenteral administrations apart from spinal administration 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)Spiradoline1.5–7.0 Nicomorphine 2–3 3.33–5 mg 20% 4 Butorphanol 2.3 4.3 mg ~12% (PO), 25–35% (SL), 70% (NAS) 3 (IM/IV) 4.5–5.5 (NAS) 5.8:1 15 minutes 3–4 hours Metopon 3 3.5 mg Oxycodone (IV/IM) or other parenteral administrations apart from spinal administration 3–4 2.5–3.33 mg (60–87 / ±75% PO) / 78.2% (IN) / 100% (IV/IM) or other parenteral administrations apart from spinal administration1.5–3 (IV/IM)5 min (IV)2–4 hours Morphine (IV/IM) or other parenteral administrations apart from spinal administration 3–4 2.5–3.33 mg 100% 3–4 3:1/4:1Instantaneously (from 5 to 15 sec; IV); 5–15 min (IM)3–7 hours Clonitazene 2–3 3.33 mg Methadone (acute) . 3–4 2.5–3.33 mg 40–90% 15–602:1 Methadone (chronic) 2.5–5 2–4 mg 40–90% 15–602:1Phenazocine3.2–4.3~2.5 mg 15 min (IV); 30 minutes (IM); 30–60 minutes (oral) 3–5 hours Diamorphine (Heroin; IV/IM) or other parenteral administrations apart from spinal administration 4–5 (IV, IM) 2–2.5 (insufflated) 2–2.5 mg 100% <0.6 (morphine prodrug)Instantaneously (from 5 to 15 sec; IV); 2 to 5 min (IM)3 to 7 hours (morphine prodrug)6-MAM6–7 (IV, IM) 1.25–1.6100% (IV, IM) <0.6 (morphine prodrug)presumably 2:1Instantaneously (from 5 to 15 sec; IV); 2 to 5 min (IM)3 to 7 hours (morphine prodrug) Dezocine 7.7–13 0.76–1.29 mg 97% (IM) 2.2 4–6 hours 5 min (IV); 5–15 min (IM/BUC); 6–8 hours (TD) Hydromorphone 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% 2–35:1 Oxymorphone 10 (SC, IV, IM)3–4(PO) 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 parenteralU-477007.51.5 mg1.5–3 Levorphanol 8 1.25 mg 70% 11–161:1Desomorphine8–101–1.25 mg~100% (IV)2–3Instantaneously (from 5 to 15 sec)(IV); 2–5 min (IM)3–4 hoursN-Phenethylnormorphine8–14Alfentanil10–250.1–0.4 mg1.5 (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 effectsTrefentanil10Brifentanil10–25Acetylfentanyl15 7-Hydroxymitragynine 17 ~0.6 mg Butyrfentanyl25Enadoline2515 μg (threshold) and 0.160 mg/kg (dissociative effects) Buprenorphine (SL) 40–80 0.25 mg 30% (SL); ~100% (TD); 65% (BUC);BUNAVAIL (buprenorphine and naloxone) buccal film, CIII [prescribing information online]. BioDelivery BioDelivery Sciences International, Inc. (BDSI), Raleigh, NC. Jun 2014. 48% (INS)Eriksen J, Jensen NH, Kamp-Jensen M, Bjarnø H, Friis P, Brewster D (1989). "The systemic availability of buprenorphine administered by nasal spray". J. Pharm. Pharmacol. 41 (11): 803–5. doi:10.1111/j.2042-7158.1989.tb06374.x 20–70, mean 373:145 min12–24 hoursN-Phenethyl-14-ethoxymetopon60160 μg Furanylfentanyl 50–100Phenomorphan60–800.13–0.16 mgN-Phenethylnordesomorphine85Phenaridine50–100 Fentanyl 50–100 0.1 mg (100 μg) IM/IV 33% (SL); 92% (TD); 89% (INS); 50% (BUC) 0.04 (IV); 7 (TD)5 min (TD/IV)30–60 minutes (IV)Metonitazene1000.1 mg/100 μgAcrylfentanyl50–100+Remifentanil100100 μg100% (IM/IV)0.05 (3–6 min context-sensitive half-life; 7–18 min elimination half-life)Instantaneously (from 5 to 15 sec)15 minutes; rapid offset of effects necessitates continuous infusion for maintenance of anesthesiaParafluorofentanyl (2-Fluorofentanyl)111Buprenorphine (Transdermal)100–1150.1 mg (100 μg)30% (SL); ~100% (TD); 65% (BUC); 48% (INS)3:145–60 minutes12–24 hours14-Cinnamoyloxycodeinone177 (median potency) 101–310 (varied potencies among test subjects)77 μg2.8% (PO); 5.8% (SC) 250:7Protonitazepyne190–20055–60 μgProtonitazene20050 μgOcfentanil20040–80 μgRo4-1539240–48020–40 μg14-Methoxymetopon500 (IV)20 μgIsotonitazene50020 μg Sufentanil 500–1,000 10–20 μg 9% (PO); 52–59% (SL); 78% (BUC); 100% (IM/IV) 4.4 2:1 1–3 min (IV); 5 min (IN); 10 min (EPD); 6–15 min (SL) 30 min (IV); 40–50 min (SL)BDPC504~20 μg Orthofluorofentanyl564~17 μgC-8813591~15 μg4-Phenylfentanyl800 Etonitazene 1,000–1,500 6.6–10 μg 3-Methylfentanyl1,000 (3-methylfentanyl, (trans)-(+-)-isomer; 6,600 (3-methylfentanyl, (cis)-(-)-isomer)N-Desetylisotonitazene2,0005–10 μgEtonitazepyne2,0005 μg Etorphine 500–2,000 3.3–10 μgOhmefentanyl6,300Acetorphine8,7001.33 μg Dihydroetorphine 12,000 0.83–10 μg (20–40 μg SL) Carfentanil 10,000 1.0 μg 7.7Lofentanil10,000–11,0004-Carboethoxyohmefentanil30,000Ohmecarfentanil30,000R-3049010,000–100,00014-Methoxymetopon1,000,000 (intrathecal & supraspinal) 0.1 μgPO: oral • BUC: buccal • SL: sublingual • TD: transdermal • IV: intravenous injection • IM: intramuscular injection • SC: subcutaneous injection • EPD: epidural injection"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.

See also Oripavine – for more on the comparative strength of oripavine derivatives

References Explanatory notes

Citations

Bibliography Books

, Extra information, including printable charts

Articles

Websites

Online opioid equianalgesia calculator Electronic calculator that includes logic for bidirectional and dose-dependent conversions