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All the PPIs except tenatoprazole are rapidly metabolized in the liver by CYP enzymes (mostly by CYP2C19 and 3A4). [82] Dissociation of the inhibitory complex is probably due to the effect of the endogenous antioxidant glutathione which leads to the release of omeprazole sulfide and reactivation of the enzyme. [83] [84]
Omeprazole, sold under the brand names Prilosec and Losec, among others, is a medication used in the treatment of gastroesophageal reflux disease (GERD), peptic ulcer disease, and Zollinger–Ellison syndrome. [1] It is also used to prevent upper gastrointestinal bleeding in people who are at high risk. [1]
[3] [4] CYP2C19 is a liver enzyme that acts on at least 10% of drugs in current clinical use, [5] most notably the antiplatelet treatment clopidogrel (Plavix), drugs that treat pain associated with ulcers, such as omeprazole, antiseizure drugs such as mephenytoin, the antimalarial proguanil, and the anxiolytic diazepam. [6]
Muscle sources of the enzymes, such as intense exercise, are unrelated to liver function and can markedly increase AST and ALT. [5] Cirrhosis of the liver or fulminant liver failure secondary to hepatitis commonly reach values for both ALT and AST in the >1000 U/L range; however, many people with liver disease have normal transaminases.
Paracetomol (3D structure) overdose is the most common cause of drug-induced liver disease. Paracetamol also known as acetaminophen, and by the brand names of Tylenol and Panadol, is usually well-tolerated in prescribed dose, but overdose is the most common cause of drug-induced liver disease and acute liver failure worldwide. [12]
The proportion of AST to ALT in hepatocytes is about 2.5:1, but because AST is removed from serum by the liver sinusoidal cells twice as quickly (serum half-life t 1/2 = 18 hr) compared to ALT (t 1/2 = 36 hr), so the resulting serum levels of AST and ALT are about equal in healthy individuals, resulting in a normal AST/ALT ratio around 1.
Other causes include: infiltrative liver diseases, granulomatous liver disease, abscess, amyloidosis of the liver and peripheral arterial disease. Mild elevation of ALP can be seen in liver cirrhosis, hepatitis, and congestive cardiac failure. Transient hyperphosphataemia is a benign condition in infants, and can reach normal level in 4 months.
The oral bioavailability of PPIs is high; 77% for pantoprazole, 80–90% for lansoprazole and 89% for esomeprazole. All the PPIs except tenatoprazole are rapidly metabolized in the liver by CYP enzymes, mostly by CYP2C19 and CYP3A4. PPIs are sensitive to CYP enzymes and have different pharmacokinetic profiles.