Objective: Amiodarone (AMD), a drug of choice to treat cardiac arrhythmias, has a narrow therapeutic index (NTI). It inhibits CYP3A4, CYP2C9, and CYP2D6 enzymes. Quercetin (QUE), a pharmacologically important bioflavonoid in vegetables and fruits, is important in treating cardiovascular comorbidities. QUE alters the bioavailability of drugs used concurrently by dual inhibition of P-glycoproteins (P-gp) and cytochrome (CYP) enzyme systems. The current study aimed to investigate the pre-treatment and co-administration effect of QUE on AMD pharmacokinetics in rats.
Materials and methods: Two separate animal trials (I and II) were planned to probe the effect of QUE on AMD pharmacokinetics by following previously cited studies. The pre-treatment group received oral doses of QUE for 14 days, and a single dose of AMD on the 15th day. Rats were administered single doses of QUE (20 mg/kg) and AMD (50 mg/kg) concurrently in a carboxymethylcellulose (CMC) in the co-administration study. Blood was collected at pre-determined time points. AMD was quantified by HPLC, and data was analyzed by PK solver software.
Results: In the pre-treated group, peak plasma concentration (Cmax) and area under the curve (AUC0-∞) of AMD were increased by 45.52% and 13.70%, respectively, while time to achieve maximum concentration (tmax), half-life (t1/2) and clearance (CL) were declined by 35.72%, 16.75%, and 11.0% respectively compared to the control. In the co-administered group, compared to controls, Cmax and AUC0-∞ were elevated to 12.90% and 7.80%, respectively, while tmax, t1/2, and CL declined by 16.70%, 2.35%, and 13.40%. Further, AMD was increased in lung tissue of both treated groups, relative to the respective controls.
Conclusions: A notable pharmacokinetic drug interaction between QUE and AMD was observed in rats and warrants possible drug interaction study in humans, suggesting AMD dose adjustment specifically in patients with arrhythmia having a pre-treatment history and simultaneous administration of QUE-containing products.