Equianalgesic Dosing of Opioids Opioid medications have differing potencies. When converting from one opioid medication to another, it is critical to understand the equivalent analgesic (equianalgesic) dose to ensure continued efficacy without untoward side effects. The dose, administration route, and therapy duration must be considered. Multiple opioid conversion charts are available. Clinicians must consider individual patient factors and the characteristics of the opioid medications and delivery systems when converting between opioid products. Closely monitor patients following conversion for efficacy and potential adverse effects. Calculation of Equianalgesic Dosages Follow these three steps to calculate equianalgesic dosages when changing to a different opioid analgesic: Step 1: Calculate the total daily dose of the current opioid. Step 2: Determine the equianalgesic dose using the appropriate conversion factor or ratio. Step 3: Reduce the new opioid analgesic dose by 33% to 50% to account for cross-tolerance, dosing ratio variation, and patient variability. Determine a new regimen based on the available dosage form(s) of the new opioid.
Clinical Case Example CD is a 32-year-old female with chronic pain. She is taking Exalgo 16 mg once daily and hydromorphone immediate-release 4 mg three times daily for breakthrough pain. The patient should be transitioned to MS Contin due to insurance issues. What dose of MS Contin should be started? Step 1: Calculate the total daily dose of the current opioid. Exalgo 16 mg once daily + hydromorphone immediate-release 4 mg three times daily = 28 mg/day hydromorphone Step 2: Determine the equianalgesic dose using the appropriate conversion factor or ratio. Oral hydromorphone to oral morphine conversion ratio: 4 28 mg hydromorphone/day × 4 = 112 mg morphine/day OR 28 mg hydromorphone = equianalgesic dose of morphine 7.5 mg 30 mg Equianalgesic dose of morphine/day = 112 mg
Step 3: Reduce dose by 33% to 50% to account for cross-tolerance; determine a new regimen based on available dosage forms of the new opioid. Total daily dose of morphine = 74 to 56 mg/day New regimen: MS Contin 30 mg every 12 hours (Total morphine dose = 60 mg/day) Prescribing of Opioids in the Management of Acute and Chronic Noncancer Pain in Adults Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. 84 It is critical to understand that pain is not only a neuronal response but also involves cognitive processes that make it a subjective experience that does not require identifiable tissue damage to be significant. 85 Pain perception may be related to the site of the pain, such as the face or eye pain. Pain in children and pregnant women has unique considerations that a specialist should evaluate. In addition, pain accompanied by other physical and psychological conditions needs to be evaluated. Masking a comorbid condition by simply treating the pain could result in exacerbating the condition. Chronic pain lasts beyond the average healing time for a given injury, operationalized as pain lasting greater than 3 months. 84 Chronic pain is often clinically distinguished as related to cancer (or other terminal illness) or noncancer/nonterminal illnesses. The physiologic purpose of acute pain is to bring attention to potential or actual tissue damage so that appropriate action can alleviate the pain (e.g., remove your finger from the hot stove). The firing rate of peripheral neurons that detect painful stimuli, known as nociceptors, leads to the interpretation of pain intensity. However, the perception of nociceptor firing may influence the painful stimulus and the sensitization of the peripheral and central nervous systems.
Table 8. Examples of 50 and 90 MME/Day for Commonly Prescribed Opioids Opioid Strength 50 MME/Day 90 MME/Day
Exceeds acetaminophen maximum daily dose 90 mg (9 tablets) 60 mg (4 tablets) 60 mg (2 tablets) ~20 mg (4 tablets)
5 mg/325 mg
50 mg (10 tablets)
Hydrocodone- acetaminophen
10 mg/325 mg
50 mg (5 tablets) 33 mg (~2 tablets) 33 mg (~1 tablet) 12 mg (< 3 tablets)
15 mg 30 mg
Oxycodone sustained release
Methadone
5 mg
Table 9. Opioid Equianalgesic Doses 83
Approximate Equianalgesic Oral Dose
Approximate Equianalgesic Intravenous Dose
Conversion Factor to Oral Morphine
Medication
Morphine Oxycodone
30 mg 20 mg
10 mg
Parenteral morphine is 3 times as potent as oral morphine. Oral oxycodone is roughly 1.5 times more potent than oral morphine. Oral hydrocodone is roughly 1.5 times more potent than oral morphine. Oral hydromorphone is about 4 to 7 times as potent as oral morphine. Parenteral hydromorphone is 20 times as potent as oral morphine. Transdermal fentanyl is ~ 80 times as potent as oral morphine.
Hydrocodone
20 to 30 mg
Hydromorphone
7 mg
1.5 mg
100 mcg (0.1 mg) 15 mcg/hour
Fentanyl
(See Table 8 to convert morphine to fentanyl transdermal patches.)
Methadone Tramadol Codeine Meperidine
Variable 300 mg 200 mg
Variable
0.1
0.15
300 mg of oral meperidine
75 mg of parenteral meperidine
Oral morphine is about 10 times more potent than oral meperidine and about twice as potent as parenteral meperidine (mg for mg).
**Note: To convert to ER/LA opioids, see conversion factors listed in Common Opioids for Chronic Pain Management
35
Powered by FlippingBook