Terminalia arjuna is a tree having an extensive medicinal potential in cardiovascular disorders. Triterpenoids are mainly responsible for cardiovascular properties. Alcoholic and aqueous bark extracts of T. arjuna, arjunic acid, arjunetin and arjungenin were evaluated for their potential to inhibit CYP3A4, CYP2D6 and CYP2C9 enzymes in human liver microsomes. We have demonstrated that alcoholic and aqueous bark extract of T. arjuna showed potent inhibition of all three enzymes in human liver microsomes with IC50 values less than 50 μg/mL. Arjunic acid, arjunetin and arjungenin did not show significant inhibition of CYP enzymes in human liver microsomes. Enzyme kinetics studies suggested that the extracts of arjuna showed reversible non-competitive inhibition of all the three enzymes in human liver microsomes. Our findings suggest strongly that arjuna extracts significantly inhibit the activity of CYP3A4, CYP2D6 and CYP2C9 enzymes, which is likely to cause clinically significant drug–drug interactions mediated via inhibition of the major CYP isozymes.

Thus, these findings of the study might be helpful for safe and effective use of C. asiatica in clinical practice. However, its in vivo interaction study in humans is still warranted.

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Withania somnifera is commonly used as a rejuvenator, whereas Centella asiatica is well known for its anxiolytic and nootropic effects. The present study aims at investigating the effect of crude extracts and principal phytoconstituents of both the medicinal plants with CYP3A4 and CYP2D6 enzyme activity in human liver microsomes (HLM). Phytoconstituents were quantified in the crude extracts of both the medicinal plants using reverse phase HPLC. Crude extracts and phytoconstituents of W. somnifera showed no significant interaction with both CYP3A4 and CYP2D6 enzymes in HLM. Of the crude extracts of C. asiatica screened in vitro, methanolic extract showed potent noncompetitive inhibition of only CYP3A4 enzyme (Ki-64.36 ± 1.82 µg/mL), whereas ethanol solution extract showed potent noncompetitive inhibition of only CYP2D6 enzyme (Ki-36.3 ± 0.44 µg/mL). The flavonoids, quercetin, and kaempferol showed potent (IC50 values less than 100 μM) inhibition of CYP3A4 activity, whereas quercetin alone showed potent inhibition of CYP2D6 activity in HLM. Because methanolic extract of C. asiatica showed a relatively high percentage content of quercetin and kaempferol than ethanol solution extract, the inhibitory effect of methanolic extract on CYP3A4 enzyme activity could be attributed to the flavonoids. Thus, co-administration of the alcoholic extracts of C. asiatica with drugs that are substrates of CYP3A4 and CYP2D6 enzymes may lead to undesirable herb-drug interactions in humans.

Objective:There is a strong association between depression and anxiety. Duloxetine, an antidepressant agent, is also used in the treatment of anxiety. Hydroxyzine is preferred over benzodiazepines in the treatment of anxiety. Present study was designed to study the impact of a combination of duloxetine with hydroxyzine in treatment of anxiety.Materials and Methods:Mice received intraperitoneal injection of normal saline (10 ml/kg), duloxetine alone (10 mg/kg), hydroxyzine alone (10 mg/kg), and hydroxyzine plus duloxetine (5 mg/kg, each).Results:The in vivo results (elevated plus maze and light/dark transition tests) showed significant anxiolytic activity with the hydroxyzine treatment than the control group. The brain monoamines were significantly increased in hippocampi, cerebral cortices, and whole brain in drug-treated groups than in the control group. The group receiving the combination showed similar results in the in vivo models and in vitro tests (brain monoamine estimations) than respective monotherapies, with the exception of a greater increase of norepinephrine levels in cerebral cortices in duloxetine-treated group.Conclusion:Combination of duloxetine with hydroxyzine is not beneficial in anxiolytic treatment than the respective monotherapies. There is a need to study the pharmacokinetic drug-drug interactions to understand the present study outcomes.

Based on our in vitro and in vivo findings and until further clinical drug interaction experiments are conducted, the co-administration of drugs, especially those primarily cleared via CYP2D catalyzed metabolism, with T. arjuna extracts should be done with caution.

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Context:Anxiety disorders are chronic, common, and often comorbid. There is an unmet need in its treatment. Aripiprazole and hydroxyzine are well-known therapeutic options used as monotherapy in clinics. They have different mechanisms and site of actions.Aim:The objective of the present study was to evaluate the anxiolytic effect of aripiprazole and hydroxyzine in combination.Materials and Methods:Swiss albino mice (male) received treatment of 5% of Tween 80 in 0.9% saline (10 ml/kg; control group), “aripiprazole alone” (1 mg/kg), “hydroxyzine alone” (3 mg/kg), and aripiprazole (0.5 mg/kg) + hydroxyzine (1.5 mg/kg) through the intraperitoneal route.Results:The in vivo outcomes (elevated plus maze, light/dark transition, and marble burying tests) of hydroxyzine monotherapy-treated group showed a significant anxiolytic activity. The combination-treated group was found to be better than control and aripiprazole-treated groups. The combination-treated group showed a significant increase in the level of serotonin in different brain regions as compared to aripiprazole-treated group but not better than the hydroxyzine group. The in vitro results were in compliance with the in vivo results. The combinational approach was found to be beneficial in anxiolytic treatment as compared to aripiprazole monotherapy. However, hydroxyzine showed better anxiolytic activity when compared to control, aripiprazole monotherapy, and combination groups.Conclusions:The anxiolytic effect of combination-treated group was found to be better than aripiprazole monotherapy and lesser than hydroxyzine monotherapy.