1. Aschenbrenner, Diane S. MS, APRN, BC

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* Ibuprofen can interfere with the cardioprotective antiplatelet effect of aspirin if taken concurrently.


The U.S. Food and Drug Administration (FDA) notified health care professionals about a potential interaction between immediate-release aspirin and ibuprofen when they are taken concurrently. After a review of the literature, the FDA now believes that a 400 mg dose of ibuprofen can interfere with the cardioprotective antiplatelet effect of low-dose aspirin (81 mg taken once daily) in the immediate-release (not enteric-coated) form. Currently there are insufficient data on the effect on aspirin's antiplatelet effect of doses of less than 400 mg of ibuprofen or of chronic dosing with more than 400 mg of ibuprofen, or on the effect produced by enteric-coated rather than immediate-release aspirin. A 400 mg dose of ibuprofen appears to interfere with the antiplatelet effect of aspirin because both are nonsteroidal antiinflammatory drugs that inhibit the enzyme cyclooxygenase (COX-1 and COX-2) to decrease inflammation. Aspirin binds irreversibly to a site on the enzyme, while ibuprofen binds reversibly to a nearby site. Apparently, when they are taken concurrently, ibuprofen binds to the receptor site, preventing aspirin from binding. When ibuprofen becomes unbound, the original quantity of aspirin, which has a short half-life, is no longer available to bind to the site and achieve its therapeutic effect because some of the dose has been eliminated. The cardioprotective effect of aspirin therapy can thereby be lost, although this is only a hypothesis-a prospective, randomized clinical trial is needed. The interaction can be minimized by carefully timing administration-if the dose of ibuprofen is taken at least 30 minutes after the dose of aspirin, the aspirin can attach to the receptor site first and its therapeutic antiplatelet effect will not be lost. Alternatively, if ibuprofen is taken at least eight hours before aspirin, the possible interaction can be successfully averted. Nurses should be aware of the possible interaction and include information on it in educational materials provided to patients taking aspirin for its cardioprotective effect.


Center for Drug Evaluation and Research. Concomitant use of ibuprofen and aspirin: potential for attenuation of the anti-platelet effect of aspirin. U.S. Food and Drug Administration. 2006 Dec 8.


* Warfarin's medication guide now includes a warning about cranberry juice.


The labeling of warfarin (Coumadin) has been revised to include a medication guide for patients. This revision does not bear any new information, but one point that might not be commonly known concerns cranberry juice, the consumption of which while taking warfarin can produce an interaction that increases the serum level of the drug, according to case reports from the United Kingdom. Cranberries and cranberry juice inhibit the cytochrome P-450 (CYP) isoenzyme system through which many drugs are metabolized, and because warfarin is metabolized primarily by the isoenzyme CYP2C9, the inhibition of this isoenzyme decreases the drug's metabolism. Nurses can print the medication guide from the FDA Web site for patients. It is important to remind the patient to read the medication guide that accompanies each prescription, as it may contain new information. To view the warfarin medication guide, go to the FDA home page (, select the word "Drugs" at the left side of the Web page, select "Drugs@FDA" at the right side of the next Web page, enter "warfarin" in the free text box, and submit the entry. Select "Coumadin" from the table, then select "Label Information" and "View the Label," at the end of which the guide is shown.


Bristol-Myers Squibb. [Label information]: Coumadin tablets (warfarin sodium tablets, USP) crystalline, Coumadin for injection (warfarin sodium for injection, USP). 2006 Apr. Suvarna R, et al. BMJ 2003;327(7429):1454.


* A new warning concerning a cancer drug and congestive heart failure.


Novartis Pharmaceuticals has revised the precautions section of the labeling of the cancer drug imatinib (Gleevec), which has indications for the treatment of Philadelphia chromosome positive chronic myeloid leukemia, Philadelphia chromosome positive acute lymphoblastic leukemia, and certain other forms of cancer, because severe congestive heart failure and left ventricular dysfunction have been reported occasionally. Most of the patients who reportedly developed those complications had comorbidities including hypertension, diabetes, and coronary artery disease, or had risk factors such as advanced age or history of cardiac disease. All patients with known cardiac disease or risk factors for cardiac failure who need treatment with imatinib should be monitored closely.


U.S. Food and Drug Administration. Dear healthcare professional [letter: 2006 Safety Alert: Gleevec (imatinib mesylate)]. 2006 Oct 19.


* Overdosage of the antidepressant venlafaxine can cause serious adverse effects or death.


The labeling of venlafaxine (Effexor and Effexor XR) has been revised to reflect postmarketing experience concerning overdosage of the drug, most commonly in combination with use of alcohol or other drugs, or both, producing tachycardia, possibly life-threatening electrocardiogram changes (prolongation of the QT and QRS intervals and bundle branch block, for example), bradycardia, hypotension, changes in level of consciousness ranging from somnolence to coma, mydriasis, seizures, rhabdomyolysis, liver necrosis, serotonin syndrome, vertigo, vomiting, and death. Overdosage of venlafaxine, which has a novel chemical structure, is more likely to result in death than is an overdosage of a selective serotonin reuptake inhibitor, but not as likely to as an overdosage of a tricyclic antidepressant. Further, because overdosage might be attributable to the greater suicidality noted in patients treated with venlafaxine, they should receive the smallest quantity of capsules consistent with good management in order to minimize the risk.


Wyeth. Dear healthcare professional [letter: Effexor XR (venlafaxine HCL) changes to prescribing information. 2006 Oct 17.