FOOD/DRUG INTERACTIONS
Putting the squeeze on half a grapefruit
My patient was warned not to drink grapefruit juice while taking his current medication regimen. He is accustomed to eating half a grapefruit at breakfast and would like to continue doing so. What should I tell him?-K.R., CALIF.
Tell him he would be taking a big risk. By delaying, decreasing, or increasing drug absorption or metabolism, grapefruit and grapefruit juice can significantly alter the effects of many drugs. Although the type and degree of risk depends on the specific medications your patient is taking, the FDA says that just two slices of grapefruit can affect how some drugs work.1
In one study, over 85 prescription and over-the-counter drugs were found to interact with grapefruit and 43 were associated with serious adverse reactions such as torsades de pointes, rhabdomyolysis, gastrointestinal bleeding, and nephrotoxicity.2 Drugs associated with an intermediate or high risk of torsades de pointes when combined with grapefruit include erythromycin, quinidine, amiodarone, and many anticancer agents.2,3 Besides grapefruit, warn your patient to avoid Seville oranges (often used to make orange marmalade) and tangelos (a cross between tangerines and grapefruit) because these fruits affect the same enzyme as grapefruit juice.1
Teach all patients to read and heed warnings about interactions on medication labels. If they have any questions about whether their medications interact with grapefruit (or any other food or drug), tell them to ask a pharmacist or the healthcare provider before consuming the forbidden fruit.
REFERENCES
1. US Food & Drug Administration. Don't take this with that! 2015. http://www.fda.gov/Drugs/ResourcesForYou/SpecialFeatures/ucm341437. [Context Link]
2. Bailey DG, Dresser G, Arnold JM. Grapefruit-medication interactions: forbidden fruit or avoidable consequences? CMAJ. 2013;185(4):309-316. [Context Link]
3. US Food & Drug Administration. Grapefruit juice and some drugs don't mix. 2017. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm292276.htm. [Context Link]
MEASLES
Vaccination indicated for this older adult?
My patient, 72, recently retired and wants to travel around the country. She's heard about occasional measles outbreaks and asked me if she would be wise to get the measles/mumps/rubella (MMR) vaccine. She doesn't think she's ever received the vaccine and has no recollection of having measles as a child. Without vaccination, is she at a high risk for contracting measles?-M.R., ILL.
No. The CDC considers adults born before 1957 to be protected from measles regardless of their vaccination status because of the likelihood that they were exposed to the virus in their childhood, when measles was endemic in the US. However, the CDC also states that receiving a dose of the MMR vaccine will not harm patients who may already be immune to measles (or to mumps and rubella).
The CDC strongly urges older adults to get vaccinated for certain other diseases, such as pneumococcal pneumonia and shingles. Before she travels, advise your patient to discuss her vaccine status with her healthcare provider to make sure she is up to date with current recommendations.
Source: Centers for Disease Control and Prevention. Frequently asked questions about measles in the U.S. http://www.cdc.gov/measles/about/faqs.html#do.
TRENDELENBURG POSITION
Thumbs up for head down
I know that the Trendelenburg position is no longer recommended to help manage acute hypotension due to multiple negative physiologic effects associated with head-down positioning. In fact, I never see it used anymore. So I was surprised when a physician asked me to place a patient in Trendelenburg position prior to inserting a central venous catheter (CVC) in the patient's subclavian vein. What is the rationale?-L.L., KY.
According to the American Society of Anesthesiologists (ASA), research indicates that in adults, the Trendelenburg position is associated with a greater increase in the diameter and cross-sectional area of the right internal jugular vein compared with supine positioning, so this position may decrease the risk of air embolism during venous access.1,2 Accordingly, the ASA strongly recommends that whenever clinically appropriate and feasible, patients be placed in the Trendelenburg or head-down position before establishing central venous access in the neck or chest.1
Although Trendelenburg position is not indicated to treat hypovolemic shock, it is still appropriately used for CVC insertion and as an emergency intervention for venous air embolism unless contraindications exist, such as morbid obesity or elevated intracranial pressure.2
REFERENCES
1. American Society of Anesthesiologists. Practice guidelines for central venous access: a report by the American Society of Anesthesiologists Task Force on Central Venous Access. Anesthesiology. 2012;116(3):539-573. [Context Link]
2. Heffner AC, Androes MP. Overview of central venous access. UpToDate. 2018. http://www.uptodate.com. [Context Link]