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1.2.7: Develop and implement individualized treatment plans, taking into consideration drug interactions

A patient presents a new prescription to you for tamoxifen. Her doctor said he was prescribing it as adjuvant treatment for breast cancer following her surgery last month. You review her medication profile and document that she is also taking metoprolol, hydrochlorothiazide, and Prozac. What is the appropriate assessment of potential drug interactions for this patient?

(A) There are no clinically significant drug interactions to alter her medication regimen.

(B) You explain that a number of SSRIs, including Prozac, have been documented to decrease the effectiveness of tamoxifen by interfering with its metabolism to an active metabolite. You will call the patient's physician to consider alternative antidepressant options.

(C) You explain that hydrochlorothiazide has been documented to decrease the effectiveness of tamoxifen by interfering with its metabolism to an active metabolite. You will call the patient's physician to consider an alternative diuretic.

(D) You explain that metoprolol has been documented to decrease the effectiveness of tamoxifen by interfering with its metabolism to an active metabolite. You will call the patient's physician to consider an alternative beta-blocker.

The Correct Answer is: B

SSRIs that are strong inhibitors of the cytochrome P450 system have been documented to decrease the effectiveness of tamoxifen by decreasing the metabolism of tamoxifen to its potent metabolite endoxifen. It would be appropriate to notify the patient's physician and discuss alternative antidepressant options (B).

There is a potentially clinically significant drug interaction between tamoxifen and Prozac (fluoxetine), (A). Hydrochlorothiazide has not been shown to interfere with the activation of tamoxifen (C). Metoprolol has not been shown to interfere with the activation of tamoxifen (D).

Which of the following is a correct statement regarding administering drugs via an enteral feeding tube?

(A) Extended-release medications are always preferable to immediate-release dosage forms.

(B) As long as tablets are crushed very finely they will retain their pharmacokinetic properties.

(C) All drugs that a patient receives should be given simultaneously to minimize feeding interruptions.

(D) Liquid medications may interact with nutritional formula and clog the feeding tube.

The correct answer is (D)

Some liquid medications have physical incompatibilities with enteral nutrition products, which may thicken the products or form a gel (D).

Immediate release dosage forms are preferred for feeding tube administration (A), as crushing extended-release products can cause all of the medication to be released immediately instead of over the intended extended timeframe. Many tablets cannot be crushed at all, and crushing often changes the ...

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