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Author: Admin | 2025-04-28
Of treatment difficult. To aid in assessing severity of pain and pain management efficacy, pain scales have been created. Three commonly used pain rating scales are the Visual Analogue Scale, the Verbal Rating Scale, and the Numerical Rating Scale.14 While enlightening, data produced from these scales can be easily misunderstood by both patients and clinicians.14 With information from a patient’s PGT and data collected from pain scales, clinicians can more closely and accurately assess a patient’s response to pain medications. Acute pain treatment guidelines for low back pain recommend the use of opioids in patients with persistent moderate-to-severe pain or after failed treatment with acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, and tramadol.15,16 Opioid use in chronic pain patients is reserved for those unresponsive to the following nonopioid treatment options: self-care, cognitive therapy, acetaminophen, tricyclic antidepressants, NSAIDs, pregabalin, gabapentin, and physical therapy.15,17 Codeine Codeine is an opioid analgesic that is related to morphine, with less potent analgesic properties. Codeine is selective for the mu receptor but with much weaker affinity than morphine. Once administered, codeine is metabolized to codeine-6-glucuronide (C6G), morphine, and norcodeine through different pathways. CYP2D6 is the major enzyme responsible for the conversion of codeine to morphine.18 Normally, a patient converts approximately 10% of codeine to morphine for analgesia. There are many combinations of alleles, which determine metabolizer status that can be detected from PGT. Approximately 1% to 2% of patients are UMs (e.g., CYP2D6*1/*1XN ) and make up to 75% more morphine than non-UMs, substantially increasing their risk of toxicity.19 Alternative analgesics are recommended for CYP2D6 UMs. EMs and IMs produce normal morphine formation (e.g., CYP2D6*1/*1 and CYP2D6*4/*10, respectively). Age- or weight-specific codeine dosing is recommended in these types of metabolizers.4 Patients who are PMs (~5%-10% of the population) have greatly reduced morphine formation, leading to insufficient pain relief (e.g., CYP2D6*3/*6 ). Codeine should be avoided in these patients due to insufficient pain relief.4 Other opioid analgesics, which are not metabolized by the CYP2D6 enzyme system to active metabolites, include morphine, hydromorphone, oxymorphone, buprenorphine, and fentanyl.20 These alternatives are potentially safer than codeine in UM patients. Please refer to CASE 1 regarding the dosing of codeine.21 Case 1. Codeine JM, a 4-year-old (27.6 kg) male, was discharged from the hospital after an overnight stay post adenotonsillectomy for treatment of recurrent tonsillitis and pediatric obstructive sleep apnea syndrome. Patient was receiving liquid codeine at age-appropriate dose (8 mg up to 5 doses a day as needed) inpatient, which was continued after discharge. Two days post discharge, after four doses, the child was brought to the hospital without vital signs. Postmortem morphine serum concentration was 17.6 ng/mL (therapeutic range 4.5 +/- 2.1 ng/mL). Blood codeine range was within the
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