Distribution, absorption, metabolism, and excretion of morphine

Morphine can be taken in various ways which include injection or through the mouth in pill or syrup form. For therapeutic purposes, injection is the most preferred way of administration.

Once the drug gets into the body, a large percentage is acted upon in the liver. Thus, if it is ingested orally, then forty to fifty percent of the intake is what ends up at the central nervous system. Following intramuscular injection or subcutaneous injection, morphine plasma amounts hit a high in about twenty minutes (Koch 205). For oral ingestion, the high is hit in about half an hour.

About eighty-seven percent of morphine intakes are excreted in the urine in seventy-two hours of administration. It is for the most part converted into morphine-3-glucuronide and morphine-6-glucuronide through the process of glucuronidation by phase two enzyme UDP-glucuronosyltransferase-2B7 (Koch 206). Metabolism rate varies with age, sex, diet, genetic orientation, sickness status, and use of any other drugs.

The excretion half-life of morphine is about two hours. However, there exist small disparities between males and females. A small amount is stored in fat and can be identified even after death (Koch 206).

Distribution, Absorption, Metabolism, and Excretion of Morphine

The modes of administration for morphine include, oral, intravenous, intrathecal, epidural, subQ, and rectal. It is also abused through inhalation. However, the most convenient route is IV. The drug is distributed in blood with a peak plasma half-life of 20 minutes. Its metabolism occurs in the liver through the Cytochrome P450 enzymes of phase I and glucuronidation to form morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M3G) during phase II reactions (Ebadi 20). The phase II reactions are catalyzed by the enzyme, UDP-glucuronosyl transferase-2B7 located in the mitochondria of the hepatocytes. Consequently, a single dose of morphine yields about 60% of M3G and 10% M6G. The process of morphine metabolism can also be facilitated in the brain and kidneys. About 87% of the metabolized morphine is excreted through urine. Therefore, the elimination half-life of morphine is about 120 minutes (Ebadi 22).