Levothyroxine sodium
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Levothyroxine sodium Loss of antinociceptive effectiveness: 2 case reports Two woman with hypothyroidism developed loss of antinociceptive effectiveness of morphine and/or oxycodone following increased dosage of levothyroxine sodium. A 45-year-old woman with fibromyalgia and osteoarthritis received oxycodone in both controlledrelease and immediate-release formulations for pain relief. On routine laboratory testing approximately 2 months prior to presentation, her TSH was noted to be 35.97 mIU/mL. Her existing dosage of levothyroxine sodium was increased from 225 to 300 µg/day [route not stated]. She subsequently presented with exacerbation of pain and pain scores approximately doubled [duration of treatment and time to onset not clearly stated]. As a consequence she had increased her use of immediate-release oxycodone [outcome not stated]. A 55-year-old woman with chronic lower back pain received morphine and oxycodone/paracetamol [acetaminophen] for pain relief. She was also prescribed cyclobenzaprine 10mg every 8 hours as needed but it was seldom used due to intolerable sedation. Following an episode of community-acquired pneumonia her TSH increased to 8.58 mIU/mL from a previous baseline of 1.84 mIU/mL 6 months prior. Her existing dosage of levothyroxine sodium was increased from 100 to 112 µg/day [route not stated]. Subsequently she presented with worsening pain control, particularly at night [duration of treatment and time to onset not clearly stated]. To compensate she had self-medicated by increasing her frequency of oxycodone/paracetamol administration from 3 to 4 doses every 24 hours. Her morphine dosage was increased and her oxycodone/paracetamol prescription amended to allow four times daily dosing [outcome not stated]. Author comment: "[T]he authors feel that the increased levothyroxine dose did not necessarily affect the pharmacokinetics of either morphine or oxycodone but may actually affect the underlying neurophysiology of pain". Matoushek TA, et al. Loss of antinociceptive effectiveness of morphine and oxycodone following titration of levothyroxine: Case reports and a brief review of published literature. Journal of Opioid Management 8: 193-198, No. 3, May-Jun 2012. Available from: URL: http://dx.doi.org/10.5055/jom.2012.0115 803078121 USA
0114-9954/10/1423-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved
Reactions 13 Oct 2012 No. 1423
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