Medication Interactions

Elizabeth Rash PhD, ARNP, FNP-C

UCF College of NursingCFP Physicians Group

Medication Interactions

• Good and Bad–Synergism

• Ex. Codeine + acetaminophen or ibuprofen = increased pain relief

–Adverse drug events (ADEs)

A BUnidirectional

A BBidirectional

Adverse Drug Events (ADEs)

• The numbers (U.S. Prescribing 2003)

• 3.4 billion Rx filled–10.1 million/yr for <65y–23.5 million/yr for >65y

Adverse Drug Events (ADEs)

• 701,547 patients treated for ADEs in EDs (2004-2005)

–116,318 hospitalized–1/3 2o allergic reactions–1/3 2o unintentional overdose –2/3rds considered to be potentially

preventable

Adverse Drug Events (ADEs)

• Most ADEs 2o 5 classes of drugs:– Insulins– Opioids (narcotics)– Anticoagulants– Amoxicillin containing antibiotics– Antihistamine containing cold products

JAMA 2006

Adverse Drug Events (ADEs)

• 21.3% > 65yr (community dwelling) at least 1 inappropriate Rx drug

• 23% of nursing home admissions due to medication problems

(J. Am. Pharm. Assoc.:Nov 2002)

Polypharmacy vs. Polymedicine

Drug Interactions: What?

• Other drugs– Coumadin® and Erythromycin increase bleeding

• Food– Grapefruit and Verapamil increase toxicity

• Herbs and supplements– St. John’s Wort and Zoloft® increase serotonin

crisis risk

• Other medical conditions or diseases– Prednisone® and Diabetes increase blood sugar

Drug Interactions: How?

• Absorption–Can slow down or speed up how rapidly the drug gets into the blood stream• Ex. antacids + tetracycline

Drug Interactions: How?

• Metabolism enzymes– Inducers: speed the metabolism of

another drug and can cause ineffectiveness

– Inhibitors: slow the metabolism of another drug and can cause toxicity or ineffectiveness• Plavix® and PPIs (Prilosec®)

– PPI inhibits the action of Plavix® a Prodrug that does not work until it Is metabolized

Drug Interactions: How?

• Receptors– Some drugs block the tissue receptors that

stop other drugs or chemicals from having action on that tissue• Could be good or bad

– Ex. Antihistamines (Claritin®) block allergens on the histamine receptors stopping allergic reactions

– Ex. Antihistamines (Ditropan®) block the cholinergic receptors and interfere with Alzheimer’s drugs like Aricept from working

Drug Interactions: How?

• Elimination–Taking an aspirin (acidic pH) with

Zegerid® (basic pH) may cause more rapid elimination of the aspirin and decrease its effect

Drug Interactions: How?

• Timing–NSAIDs (Motrin®) interfere with

the platelet benefits of a preventive Aspirin.

• If taking both, take the aspirin first and wait at least 2 hours before taking the Motrin®

Common Drug Interactions

• Antifungal drugs that end in "-azole”, Itraconazole or Sporanox®)

• Some antibiotics (end in "-mycin” Erythromycin®)

• Antacids cimetidine (Tagamet®)• Drugs that prevent convulsions, (Dilantin®

and Tegretol®).• Cholesterol drugs such as statins (Lipitor®)• Blood thinning drugs (Coumadin®)

Drug Interactions: Preventing ADEs

• Brown bag or drug list to all providers• ID bracelets• Use 1 pharmacy• Pharmacist consultation• Communicate side effects and don’t

stop abruptly without discussing with provider

• Follow instructions

Questions?

Thank you!

CFP Physicians Group985 SR 436 Casselberry Fl 32707(407) 831-5252

http://cfpphysiciansgroup.com/