A nurse is reviewing the medication list of a client who uses echinacea as a CAM product to boost his immune system function. The nurse should identify that echinacea may interact with which of the following conventional drugs? (Select all that apply.)

Choice A reason: This statement is incorrect and inappropriate for identifying the interaction between echinacea and lisinopril. Echinacea does not interact with lisinopril, an ACE inhibitor for blood pressure. There is no evidence that echinacea affects the blood pressure or the pharmacokinetics of lisinopril¹².

Choice B reason: This statement is incorrect and inappropriate for identifying the interaction between echinacea and amoxicillin. Echinacea does not interact with amoxicillin, a penicillin antibiotic for infection. There is no evidence that echinacea affects the antibacterial activity or the pharmacokinetics of amoxicillin¹².

Choice C reason: This statement is correct and appropriate for identifying the interaction between echinacea and prednisone. Echinacea may interact with prednisone, a corticosteroid for inflammation, by reducing its effectiveness or increasing its side effects. Echinacea has immunostimulatory properties that may counteract the immunosuppressive effects of prednisone¹². Echinacea may also induce the enzyme cytochrome P450 3A4, which is involved in the metabolism of prednisone, and decrease its blood level¹². Furthermore, echinacea may increase the risk of infection or bleeding in people who take prednisone¹².

Choice D reason: This statement is incorrect and inappropriate for identifying the interaction between echinacea and metformin. Echinacea does not interact with metformin, a biguanide for diabetes mellitus. There is no evidence that echinacea affects the blood glucose or the pharmacokinetics of metformin¹².

Choice E reason: This statement is correct and appropriate for identifying the interaction between echinacea and fluoxetine. Echinacea may interact with fluoxetine, an SSRI for depression, by increasing its side effects or toxicity. Echinacea may inhibit the enzyme cytochrome P450 2D6, which is involved in the metabolism of fluoxetine, and increase its blood level¹². Echinacea may also increase the risk of serotonin syndrome, a potentially life-threatening condition caused by excessive serotonin in the brain, in people who take fluoxetine¹²..

Choice A reason: This statement is incorrect and inappropriate for describing the interaction between ginkgo biloba and warfarin. Ginkgo biloba does not enhance the absorption of warfarin and increase its blood level. In fact, ginkgo biloba may induce the enzyme cytochrome P450 3A4, which is involved in the metabolism of warfarin, and reduce its blood level¹². However, this effect may not be clinically significant, as warfarin has two enantiomers (R- and S-warfarin) that are metabolized by different enzymes, and S-warfarin is more potent than R-warfarin¹².

Choice B reason: This statement is incorrect and inappropriate for describing the interaction between ginkgo biloba and warfarin. Ginkgo biloba does not reduce the metabolism of warfarin and prolong its action. As mentioned above, ginkgo biloba may induce the enzyme cytochrome P450 3A4, which is involved in the metabolism of warfarin, and reduce its blood level¹². However, this effect may not be clinically significant, as warfarin has two enantiomers (R- and S-warfarin) that are metabolized by different enzymes, and S-warfarin is more potent than R-warfarin¹².

Choice C reason: This statement is correct and appropriate for describing the interaction between ginkgo biloba and warfarin. Ginkgo biloba may increase the therapeutic effect of warfarin and the risk of bleeding by inhibiting platelet aggregation and interfering with clotting factors¹². Ginkgo biloba contains flavonoids and terpenoids that have antiplatelet and anticoagulant properties¹². Therefore, taking ginkgo biloba with warfarin may increase the risk of bleeding complications, such as hemorrhage or intracranial hemorrhage¹²³.

Choice D reason: This statement is incorrect and inappropriate for describing the interaction between ginkgo biloba and warfarin. Ginkgo biloba does not interfere with the monitoring of warfarin and its INR value. INR stands for international normalized ratio, which is a measure of how long it takes blood to clot. Warfarin therapy requires regular monitoring of INR to ensure that the dose is appropriate and effective¹². Ginkgo biloba does not affect the INR test itself, but it may affect the INR value by increasing the anticoagulant effect of warfarin¹². Therefore, taking ginkgo biloba with warfarin may require more frequent monitoring of INR to adjust the dose of warfarin accordingly¹².