Is phenobarbital an inducer enzyme?
Phenobarbital is a potent enzyme inducer known for hepatotoxicity and for inducing its own metabolism.
Which drugs commonly interact with cytochrome P450?
Cytochrome P450 enzymes can be inhibited or induced by drugs, resulting in clinically significant drug-drug interactions that can cause unanticipated adverse reactions or therapeutic failures. Interactions with warfarin, antidepressants, antiepileptic drugs, and statins often involve the cytochrome P450 enzymes.
Is phenobarbital a CYP3A4 inducer?
The liver and small intestine have the highest CYP3A4 activity. Potent inhibitors of CYP3A4 include clarithromycin, erythromycin, diltiazem, itraconazole, ketoconazole, ritonavir, verapamil, goldenseal and grapefruit. Inducers of CYP3A4 include phenobarbital, phenytoin, rifampicin, St. John’s Wort and glucocorticoids.
What does Phenobarbital induce?
In elderly patients, it may cause excitement and confusion, while in children, it may result in paradoxical hyperactivity. Phenobarbital is a cytochrome P450 hepatic enzyme inducer. It binds transcription factor receptors that activate cytochrome P450 transcription, thereby increasing its amount and thus its activity.
What drugs are metabolized by the cytochrome P450 3a4 pathway?
Cytochrome P450 enzymes metabolize approximately 60% of prescribed drugs, with CYP3A4 responsible for about half of this metabolism; substrates include acetaminophen, codeine, ciclosporin (cyclosporin), diazepam, and erythromycin. The enzyme also metabolizes some steroids and carcinogens.
What drugs are metabolized by cyp3a5?
The enzyme metabolizes drugs such as nifedipine and cyclosporine as well as the steroid hormones testosterone, progesterone and androstenedione. This gene is part of a cluster of cytochrome P450 genes on chromosome 7q21.
How is phenobarbital metabolized?
Phenobarbital is metabolized in the liver by CYP2C9 with minor metabolism by CYP2C19 and CYP2E1. A quarter of the dose of phenobarbital is excreted unchanged in the urine. In adults, the half-life of phenobarbital is 100 hours and in term and preterm infants is 103 and 141 hours, respectively.
How do you remember CYP450 inhibitors and inducers?
Cytochrome P450 (CYP450) enzymes can be inhibited or induced by some drugs, resulting in significant drug interactions that can cause unanticipated adverse reactions or therapeutic failures. An easy way to remember the mnemonic is; CRAP GPs spend all day on SICKFACES.com.
Which is an inducer of the cytochrome P450 gene?
Transcriptional activation of cytochrome P450 (CYP) genes and various drug metabolizing enzymes by the prototypical inducer phenobarbital (PB) and many other drugs and chemicals is an adaptive response of the organism to exposure to xenobiotics.
What are the side effects of cytochrome P450?
Sedation, lethargy, depression, unsteadiness, stupor, and coma have been reported. Paradoxical excitement, restlessness, and confusion may occur in the elderly, and hyperkinesia may be a problem in children. Megaloblastic anemia (sometimes responsive to folic acid) and osteomalacia may occur after prolonged use.
How are barbiturates inhibited by other CYPs?
Definition. Acutely, barbiturates interact with various CYPs and inhibit the biotransformation of other CYP substrates; likewise, other substrates (e.g., other drugs or endogenous substrates) can inhibit the barbiturate metabolism. Chronic use of barbiturates will cause upregulation, or induction, of the microsomal enzymes (CYPs 1A2, 2C9, 2C19,…
What kind of juice inhibits the P450 enzyme?
Grapefruit juice, which inhibits some P-450 enzymes, has been found to increase the bioavailability of some dihydropyridine calcium antagonists.
