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
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. In most patients, acute pain resolves when the affected tissue heals; however, some patients progress from acute to chronic pain in a process called pain chronification. The underlying cause(s) is/are not established but may be related to central nervous system changes in pain facilitation and inhibition. 86 Pain chronification is based on acute pain (e.g., low back, postsurgical, diabetic neuropathy) and social and psychological factors, including maladaptive pain, coping behaviors, concurrent psychiatric illness,
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.
Book Code: MDCO1025
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