Pattern of Retinopathy: Although the locus of toxic damage is parafoveal in many eyes, Asian patients often show an extramacular pattern of damage. Dose: We recommend a maximum daily HCQ use of 5.0 mg/kg real weight, which correlates better with risk than ideal weight. Plaquenil exfoliative dermatitis Plaquenil and weed Cytochromes P450 CYP are a major source of variability in drug pharmacokinetics and response. Of 57 putatively functional human CYPs only about a dozen enzymes, belonging to the CYP1, 2, and 3 families, are responsible for the biotransformation of most foreign substances including 70–80% of all drugs in clinical use. Metabolism/Elimination Hydroxychloroquine is metabolized by dealkylation in the liver, primarily by CYP2C8 and CYP3A4 enzymes. The 3 major metabolites of hydroxychloroquine—desethylchloroquine, desethylhydroxychloroquine, and bisdesethylchloroquine—are pharmacologically active and have longer elimination half-lives than the half-life of the parent compound. 7,13 Cytochrome P450 enzymes are the main xenobiotic inactivators in humans. The main families of CYP450 enzymes involved in drug metabolism are the monooxygenases of the CYP1, CYP2 and CYP3 families. Prescribers need to be aware of drug interactions with any of these enzymes that may alter responses to any other prescribed medications. Risk of Toxicity: The risk of toxicity is dependent on daily dose and duration of use. There are no similar demographic data for CQ, but dose comparisons in older literature suggest using 2.3 mg/kg real weight. Hydroxychloroquine metabolism cyp Recommendations on Screening for Chloroquine and., Hydroxychloroquine Information for Providers AIDSinfo Chloroquine diphosphate salt storageChloroquine resistance tanzaniaMaker of plaquenil Hydroxychloroquine Hydroxyzine Imatinib Levomepromazine Methadone Metoclopramide Mibefradil Midodrine Moclobemide Nefazodone Norfluoxetine Paroxetine Perphenazine Propafenone Propoxyphene Propranolol Quinacrine Quinidine. Cytochrome P450 CYP450 Enzyme Inhibitors Drug Reference Table. Medication & Herbal Inhibitors of the Cytochrome P450 CYP.. Drug metabolism Pharmacology Education Project. Plaquenil hydroxychloroquine sulfate dose, indications.. The proposed mechanism is inhibition of CYP450 2D6 hepatic metabolism by hydroxychloroquine. In a randomized, double-blind, crossover study, seven healthy subjects with CYP450 2D6 extensive metabolizer phenotypes took 400 mg hydroxychloroquine or placebo twice daily for 8 days, and 100 mg metoprolol orally on the ninth day. Average metoprolol. Enantiomer-specific analysis revealed genotype-dependent enantio-selective metabolism, with nearly 40% greater R- vs S-metoprolol metabolism in ultra-rapid and extensive metabolizers. This study demonstrates a marked effect of CYP2D6 metabolizer phenotype on metoprolol pharmacokinetics and confirms enantiomer specific metabolism of metoprolol. CYP2C19 and CYP3A4 are the major players in the metabolism of benzodiazepines that undergo phase I metabolism figure 1. Phase I metabolism tends to be reduced in the elderly, along with polypharmacy, predisposing elderly patients to CYP450 related interactions. However, phase II metabolism remains relatively preserved in the elderly.