Equianalgesic

An equianalgesic (or opioid) 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]

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]

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).[3] 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.[4] 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.[5] 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.[6]

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 commonly used opioid drugs and their relative potencies. Values for the potencies of opioids listed on this table are given as taken orally unless another route of administration is provided. As such, their bioavailabilities differ, and they may be more potent when taken intravenously. 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 due to methadone being stored in fat tissue, thus giving higher serum levels with longer use. 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, this effect becomes less significant again with even longer use as tolerance develops.

<span style:"font-size:x-large;">Opioid Equivalency Table
(morphine, PO)
Analgesic Strength
(relative)		 Equivalent dose
(10 mg oral morphine)		 Bioavailability Half-life of active metabolites
(hours)
Acetaminophen (non-opioid)  1⁄360 3600 mg 63–89%
Aspirin (NSAID, non-opioid)  1⁄360 3600 mg 80–100% 3.1–9
Ibuprofen[7] (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[7] (NSAID, non-opioid)  1⁄138 1380 mg 95% 12–24
Dextropropoxyphene[8]  1⁄13 to  1⁄20 130–200 mg
Codeine  1⁄10 180 mg (PO) ≈90% 2.5–3 (C6G 1.94;[9] morphine 2–3)
Tramadol  1⁄10 >200 mg 75% (IR), 85–90% (ER) 5.5–7 (≈9)
Tapentadol  3⁄10[10] 32 mg 32% (fasting)
Tilidine  1⁄5 50 mg
Dihydrocodeine  1⁄5 50 mg 20% 4
Anileridine[11]  1⁄4 40 mg
Alphaprodine  1⁄4– 1⁄6 40–60 mg
Pethidine (meperidine hydrochloride)  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)[12] 1 10 mg SC/IV/IM, 150 mg PO
Morphine (oral) (1) (10 mg) (30 mg PO) ≈25%
Oxycodone[13] 1.5 6.67 mg ≤87% 3–4.5
Spiradoline 1.5
Morphine (IV/IM) 3 3.33 mg 100% 2–3
Clonitazene 3 3.33 mg
Methadone (acute)[14][15] 3–4 2.5–3.33 mg 40–90% 15–60
Methadone (chronic)[15] 2.5–5 3.33  mg 40–90% 15–60
Phenazocine 4[3] ~2.5 mg
Diamorphine (heroin; IV/IM)[16] 4–5 2–2.5 mg 100% <0.6
Dezocine 4-6 1.6-2.5 mg 97% (IM) 2.2
Hydromorphone[17] 5 1.5 mg SC/IV/IM, 7.5 mg PO 62% 2–3
Oxymorphone[13] 7 10 mg PO, 1 mg IV 10% 7.25–9.43
U-47700 7.5
Levorphanol[18] 8 1.25 mg 70% 11–16
Desomorphine (Krokodil) 8-10 1 mg- 1.25 mg ~100% (IV) 2-3
N-Phenethylnormorphine 8-14
Alfentanyl 10-25
Trefentanil (10-25)+
Brifentanil (10-25)+
Acetylfentanyl 15
7-Hydroxymitragynine 17 ≈.6 mg
Furanylfentanyl 20
Butyrfentanyl 25
Enadoline 25
Buprenorphine[8] 40 0.4 mg 35–40% (SL) 20–70, mean 37
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 mcg) IM/IV 33% (SL); 92% (TD) 0.04 (IV); 7 (TD)
Acrylfentanyl (50–100)+
14-Cinnamoyloxycodeinone 177
Remifentanil 100-200 0.1 mg - 50 mcg
Ocfentanil 125–250 40–80 mcg
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 1,000–12,000 20–40 µg
2-Fluorohmefentanil 18,000
4-carboethoxyohmefentanil 30,000
R-30490 (10,000–100,000)-
Carfentanil[18] 10,000–100,000 0.1–1.0 μg 7.7
Lofentanil (10,000–100,000)+
"Strength" is defined as analgesic potency relative to morphine.
Tolerance, sensitization, cross-tolerance, metabolism, and hyperalgesia may be complex factors in some individuals.
Interactions caused by polypharmacy, food and drink, and other factors may potentiate or inhibit the effectiveness of certain analgesics as well as drastically alter their halflife.
Because some analgesics are prodrugs, individual variation in liver enzymes (e.g., enzyme CYP2D6) may result in significantly altered effects.

See also

Notes

    References

    1. 1 2 Joishy, S. K. (1999). Palliative medicine secrets. Philadelphia PA: Hanley & Belfus. p. 97. ISBN 1-56053-304-8.
    2. ↑ McPherson, Mary Lynn M. (2000). Demystifying Opioid Conversion Calculations: A Guide for Effective Dosing. Bethesda MD: American Society of Health-System Pharmacists. p. 5. ISBN 1-58528-198-0.
    3. ↑ McPherson 2000, p. 3
    4. ↑ McPherson 2000, p. 4
    5. ↑ McPherson 2000, p. 8
    6. ↑ McPherson 2000, p. 9
    7. 1 2 "Dosing Guidelines for Acetaminophen and Selected NSAIDs" (PDF). www3.us.elsevierhealth.com.
    8. 1 2 "Ch. 4 Narcotics: Synthetic Narcotics: Dextropropoxyphene". Drugs of Abuse. Drug Enforcement Administration, U.S. Department of Justice. 2005.
    9. ↑ 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 2867071Freely accessible. PMID 20444020.
    10. ↑ "Equianalgesic Dosing of Opioids for Pain Management" (PDF). August 2012.
    11. ↑ "Anileridine". DrugBank Version: 3.0. DrugBank.
    12. ↑ "TALWIN (pentazocine lactate) injection, solution". DailyMed. National Institute of Health. Retrieved 2011-12-10.
    13. 1 2 "Equianalgesic Conversion". GlobalRPH.
    14. ↑ Tabla de equivalencia opiáceos
    15. 1 2 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.
    16. ↑ 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.
    17. ↑ Paul Walker. "MORPHINE vs HYDROMORPHINE vs OXYCODONE vs THE PATCH". Archived from the original on December 24, 2001.
    18. 1 2 "Levorphanol". DrugBank Version: 3.0. DrugBank.

    External links

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