Equianalgesic

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.[1] Tables of this general type are also available for NSAIDs, benzodiazepines, depressants, stimulants, anticholinergics and others as well.

Format

Equianalgesic tables are available in different formats, such as pocket-sized cards for ease of reference.[1] 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.[2][3]

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).[4] 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.[5] 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-naïve 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.[6] 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.[7][3][8]

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 vs mass of medication. Not all medications have a fixed relationship on this scale. Methadone is different from most opioids considering 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[lower-alpha 1]
Analgesic Strength
(relative)		 Equivalent dose
(10 mg oral morphine)[lower-alpha 2]		 Bioavailability Half-life of active metabolites
(hours)		 Oral-to-parenteral ratio Speed of onset Duration
Paracetamol (non-opioid) ​1⁄360 3600 mg 63–89% 1–4 37 min (PO); 8 min (IV) 5 – 6 hours
Aspirin (NSAID, non-opioid) ​1⁄360 3600 mg 80–100% 3.1–9
Ibuprofen[10] (NSAID, non-opioid) ​1⁄222 2220 mg 87–100% 1.3–3
Diflunisal (NSAID, non-opioid) ​1⁄160 1600 mg 80–90% 8–12
Naproxen[10] (NSAID, non-opioid) ​1⁄138 1380 mg 95% 12–24
Piroxicam (NSAID non-opioid) ​1⁄120 (est.)
Indomethacin (NSAID non-opioid) ​1⁄64 (est.)
Diclofenac[10][11] (NSAID, non-opioid) ​1⁄14 (est.) 160 mg (est.) 50–60% 1–4
Nefopam (Centrally-acting non-opioid) ​5⁄8 (est.)
Dextropropoxyphene[12] ​1⁄13–​1⁄20 130–200 mg
Codeine ​1⁄10–​3⁄20 100–120 mg (PO) ~90% 2.5–3 (C6G 1.94;[13] morphine 2–3) 15–30 min (PO) 4–6 hours
Tramadol ​1⁄10 ~100 mg 75% (IR), 85–90% (ER) 6.0–8.8[14] (M1)
Opium (oral) ​1⁄10 ~100 mg ~25% (morphine) 2.5–3.0 (morphine, codeine)
Tilidine ​1⁄10 100 mg
Dihydrocodeine ​1⁄5 50 mg 20% 4
Anileridine[15] ​1⁄4 40 mg
Alphaprodine ​1⁄4–​1⁄6 40–60 mg
Tapentadol[16] ​3⁄10 32 mg 32% (fasting)
Pethidine (meperidine) ​1⁄3 30 mg SC/IM/IV, 300 mg (PO) 50–60% 3–5
Benzylfentanyl ​1⁄2
AH-7921 ​4⁄5
Hydrocodone 1 10 mg =80% 3.8–6
Metopon 1 10 mg
Pentazocine lactate (IV)[17] 1 10 mg SC/IV/IM, 150 mg (PO)
Morphine (oral) 1 10 mg ~25% 2-4 3:1 30 min (PO) 3–5 hours
Oxycodone[18] 1.5 6.67 mg 60 - 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)[19]
Spiradoline 1.5
Nicomorphine 2–3 3.33–5 mg 20% 4
Morphine (IV/IM) 3 3.33 mg 100% 2–3 3:1 5 min (IV); 15 min (IM) 3–7 hours
Clonitazene 3 3.33 mg
Methadone (acute)[20][21] 3–4 2.5–3.33 mg 40–90% 15–60 2:1
Methadone (chronic)[21] 2.5–5 2-4 mg 40–90% 15–60 2:1
Phenazocine 4 ~2.5 mg
Diamorphine (heroin; IV/IM)[22] 4–5 2–2.5 mg 100% <0.6 Instantaneously (from 5 - 15 sec)(IV); 2 - 5 min (IM) 4 to 5 hours
Dezocine 4–6 1.6–2.5 mg 97% (IM) 2.2
Hydromorphone[23][24][16] 10–15 (sc),(iv),(im)
3.75–5 (po)		 0.75 mg (sc,iv,im)
2 mg (po)		 62% 2–3 5:1
Oxymorphone[18] 3 3.33 mg (PO), 1 mg (IV,IM & Interlaminar) 10%–PO , ≈ 25% Sublabial , ≈ 28% Buccal , (35% - 40%) Sublingual & Intranasal 43% BA. 7.25–9.43 35 min (PO), Instantaneously (from 5 - 15 sec)(IV) 6–8 hours
U-47700 7.5 1.5 mg 1.5-3
Levorphanol[25] 8 1.25 mg 70% 11–16 1:1
Desomorphine (Krokodil) 8–10 1–1.25 mg ~100% (IV) 2–3 Instantaneously (from 5 - 15 sec)(IV); 2 - 5 min (IM) 3 – 4 hours
N-Phenethylnormorphine 8–14
Alfentanyl 10–25 1.5 (90–111 minutes) Instantaneously (from 5 - 15 sec); 4x more rapid than fentanyl 0.25 hr (15 min); up to 54 minutes until offset of effects
Trefentanil (10–25)+
Brifentanil (10–25)+
Acetylfentanyl 15
7-Hydroxymitragynine 17 ~0.6 mg
Furanylfentanyl 20
Butyrfentanyl 25
Enadoline 25 15 ug (Threshold)and .160 mg/kg (Dissociative effects)
Buprenorphine (SL)[12] 40 0.25 mg 30%(SL);[26] ~100% (TD); 65% (buccal);[27][28] 48% (INS)[29] 20–70, mean 37 3:1 45 min 12–24 hours
N-Phenethyl-14-ethoxymetopon 60
Etonitazene 60 160 µg
Phenomorphan 60–80 0.13–0.16 mg
N-Phenethylnordesomorphine 85
Phenaridine (50–100)−
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)
Acrylfentanyl (50–100+)
Buprenorphine (Transdermal)[30][31] 100-115 0.1 mg (100 µg) 30%(SL);[26] ~100% (TD); 65% (buccal);[27][28] 48% (INS)[29] 3:1 45–60 minutes 12–24 hours
14-Cinnamoyloxycodeinone 177
Remifentanil 100–200 50–100 µg 0.05 (3 minutes context-sensitive half-life; 7-18 minutes elimination half-life) Instantaneously (from 5 - 15 sec) 15 minutes; rapid offset of effects necessitates continuous infusion for maintenance of anesthesia
Ocfentanil 125–250 40–80 µg
Ro4-1539 240–480
Sufentanil 500–1,000 10–20 µg 4.4
BDPC 504 ~20 µg
C-8813 591
4-Phenylfentanyl 800
3-Methylfentanyl 1000–1500
Etorphine 1,000–3,000 3.3–10 µg
Ohmefentanyl 6300
Acetorphine 8700
Dihydroetorphine[32] 1,000–12,000 0.83–10 µg (20–40 µg SL)
2-Fluorohmefentanil 18,000
4-Carboethoxyohmefentanil 30,000
R-30490 (10,000–100,000)−
Carfentanil[33] 10,000 1.0 µg 7.7
Lofentanil (10,000–100,000)+
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.

Notes
  1. Approximate. There is a wide range of values in controlled trials[9]
  2. 10 mg oral morphine is equivalent to n mg analgesic drug x, e.g. 10 mg morphine is equivalent to 3600 mg paracetamol or 1.5 mg hydromorphone

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

References
  1. Joishy 1999.
  2. McPherson 2009, p. 5.
  3. Natusch 2012.
  4. McPherson 2009, p. 3.
  5. McPherson 2009, p. 4.
  6. McPherson 2009, p. 8.
  7. McPherson 2009, p. 9.
  8. Anderson et al 2001.
  9. Pereira et al 2001.
  10. "Dosing Guidelines for Acetaminophen and Selected NSAIDs" (PDF). www3.us.elsevierhealth.com.
  11. http://www.emedexpert.com/compare-meds/diclofenac-vs-naproxen.shtml
  12. "Ch. 4 Narcotics: Synthetic Narcotics: Dextropropoxyphene". Drugs of Abuse. Drug Enforcement Administration, U.S. Department of Justice. 2005. Archived from the original on 2006-11-02.CS1 maint: bot: original URL status unknown (link)
  13. KuKanich B (February 2010). "Pharmacokinetics of acetaminophen, codeine, and the codeine metabolites morphine and codeine-6-glucuronide in healthy Greyhound dogs". J. Vet. Pharmacol. Ther. 33 (1): 15–21. doi:10.1111/j.1365-2885.2009.01098.x. PMC 2867071. PMID 20444020.
  14. "ULTRAM® (tramadol hydrochloride) Tablets Full Prescribing Information" (PDF). US Food and Drug Administration. Ortho-McNeil Pharmaceutical, Inc. March 2008. p. 4. Retrieved December 28, 2016. The mean terminal plasma elimination half-lives of racemic tramadol and racemic M1 are 6.3 ± 1.4 and 7.4 ± 1.4 hours, respectively. The plasma elimination half-life of racemic tramadol increased from approximately six hours to seven hours upon multiple dosing.
  15. "Anileridine". DrugBank Version: 3.0. DrugBank.
  16. Cupp 2012.
  17. "TALWIN (pentazocine lactate) injection, solution". DailyMed. National Institute of Health. Retrieved 2011-12-10.
  18. "Equianalgesic Conversion". GlobalRPH.
  19. Sunshine, A.; Olson, N.; Colon, A.; Rivera, J.; Kaiko, R.F.; Fitzmartin, R.D.; Reder, R.F.; Goldenheim, P.D. (July 1996). "Analgesic Efficacy of Controlled‐Release Oxycodone in Postoperative Pain". Journal of Clinical Pharmacology. 36 (7): 595–603. doi:10.1002/j.1552-4604.1996.tb04223.x. PMID 8844441.
  20. Tabla de equivalencia opiáceos
  21. Manfredonia JF (March 2005). "Prescribing methadone for pain management in end-of-life care". J Am Osteopath Assoc. 105 (3 Suppl 1): S18–21. PMID 18154194. Table 2: Conversion Ratio of Oral Morphine to Methadone.
  22. Reichle CW, Smith GM, Gravenstein JS, Macris SG, Beecher HK (April 1962). "Comparative analgesic potency of heroin and morphine in postoperative patients". J. Pharmacol. Exp. Ther. 136 (1): 43–6. PMID 14491157.
  23. Toronto Surgery 2014.
  24. Walker 2001.
  25. "Levorphanol". DrugBank Version: 3.0. DrugBank.
  26. Mendelson J, Upton RA, Everhart ET, Jacob P 3rd, Jones RT (1997). "Bioavailability of sublingual buprenorphine". Journal of Clinical Pharmacology. 37 (1): 31–7. doi:10.1177/009127009703700106. PMID 9048270
  27. "Buprenorphine / Naloxone Buccal Film (BUNAVAIL) C-III" (PDF). Pharmacy Benefits Management (PBM) Services. September 2014.
  28. BUNAVAIL (buprenorphine and naloxone) buccal film, CIII [prescribing information online]. BioDelivery BioDelivery Sciences International, Inc. (BDSI), Raleigh, NC. Jun 2014.
  29. 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
  30. Khanna, IK; Pillarisetti, S (2015). "Buprenorphine - an attractive opioid with underutilized potential in treatment of chronic pain". Journal of pain research. 8: 859–70. doi:10.2147/JPR.S85951. PMID 26672499
  31. Cote, J; Montgomery, L (July 2014). "Sublingual buprenorphine as an analgesic in chronic pain: a systematic review". Pain medicine (Malden, Mass.). 15 (7): 1171–8. doi:10.1111/pme.12386. PMID 24995716
  32. Ohmori, Satoshi; Morimoto, Yasunori (2002). "Dihydroetorphine: a potent analgesic: pharmacology, toxicology, pharmacokinetics, and clinical effects". CNS Drug Reviews. 8 (4): 391–404. doi:10.1111/j.1527-3458.2002.tb00236.x. ISSN 1080-563X. PMC 6741694. PMID 12481194. Dihydroetorphine (DHE) is one of the strongest analgesic opioid alkaloids known; it is 1000 to 12,000 times more potent than morphine. ...
         MOR is the most commonly used opioid analgesic for pain relief, and its oral daily dose (20 to 1000 mg) is relatively high (44). On the other hand, DHE produces rapid analgesic effects at an extremely low dose, 20 ìg sublingually in humans (60, 78). ...
  33. "Carfentanil". DrugBank Version: 3.0. DrugBank.

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