课件：多瑞吉消化道癌痛治疗优势.ppt

* * 以胰腺癌为例 * * 以胰腺癌为例 * * * * * * Intestine Opioid is released from the controlled release tablet in the intestine. The preparations MS Contin and OxyContin release constant levels of drug over a period of 12 hours and must be taken twice daily. Opioid is absorbed into the bloodstream from the intestine. The GI tract contains opioid receptors and exposure to opioid can lead to constipation. Liver Opioid reaches the liver via the hepatic portal circulation. Consequently, there is first pass metabolism and as much as 60% of morphine and 13-40% of oxycodone is metabolized at this point. Patients with hepatic impairment show elevate peak plasma levels of oxycodone that are 95% greater than normal. Circulation Opioid levels are maintained in circulation for 12 hours after dosing. Steady state levels are attained after 24-36 hours of repeated bid dosing of OxyContin. Significant peak an trough serum concentrations occur even with repeated doses of MS Contin. Brain Opioids must pass through the blood-brain barrier. The analgesic effects of opioids result from their activity as mu opioid receptor agonists. Kidney Morphine and oxycodone and their active metabolites are excreted via the kidney. Patients with renal impairment show elevated plasma levels of opioid and active metabolite * * Skin Fentanyl diffuses out of the Duragesic patch and accumulates in the skin tissues beneath. Circulation Fentanyl enters the systemic circulation directly from the skin. The lipophilic molecule, nevertheless has a high affinity for skin tissues and is therefore released at a slow predictable rate. Brain Fentanyl passes readily through the blood-brain barrier. The analgesic effects of fentanyl result from its activity as a pure mu receptor agonist. Liver Only very small amounts of fentanyl reach the liver at any one time and Duragesic is unlikely to cause changes in the serum levels of other drugs by interacting with liver enzymes. Fentanyl is metabolized to a single inactive metaboli