TJ, a 45-year-old woman, comes to the pharmacy counter with a new prescription for atenolol 50 mg once daily. Her prescription profile shows that she is diagnosed with high blood pressure and is currently taking hydrochlorothiazide 25 mg once daily. When handing the prescription to the pharmacist, TJ remarks, “I’ve heard that certain juices interact with heart medications.” She wants to know if atenolol has such an interaction, because she is a frequent orange juice drinker.
How should the pharmacist counsel TJ?
PD is a 40-year-old man who comes to your pharmacy with a new prescription for simvastatin 80 mg once daily. PD notes he just came from his doctor’s office after his annual physical, where his doctor informed him his current dose of simvastatin (Zocor) 40 mg was not lowering his “bad cholesterol” to the desired level. PD and his doctor decided to try a higher dose of simvastatin before switching or adding medications. The pharmacist checks PD’s medication profile and sees he is taking no other medications.
How should the pharmacist handle this prescription?
Case 1: Fruit juices have been known to interact with certain prescription medications. Many patients are aware of the often touted grapefruit juice and statin interaction, whereby grapefruit juice (typically in large quantities; ie, greater than 1 qt) inhibits certain statins’ metabolism via the cytochrome P450 3A4 isoenzyme, resulting in increased drug levels and potential toxicity. Grapefruit, orange, and even apple juice can also interact with oral medications by inhibiting their organic anion transporting polypeptide (OATP)-mediated absorption. Many medications—including the beta1- blocker atenolol—act as substrates for this transporter (more specifically, OATP1A2). Fruit juices contain flavonoids (naringin in grapefruit and hesperidin in orange juice) that can inhibit OATPmediated uptake of atenolol, reducing systemic exposure by approximately 40%, and potentially reducing the drug’s clinical effectiveness. The pharmacist should advise TJ to take her atenolol with water and to space it 2 to 4 hours from any fruit juice intake. By doing so, TJ can be certain that her atenolol is not interacting with fruit juices.
Case 2: The pharmacist should not fill this prescription and should instead contact PD’s prescriber to inform him/her of the FDA’s new restriction on simvastatin dosing. In June 2011, the FDA mandated that simvastatin 80 mg not be initiated in new patients or in patients taking lower doses of the drug due to an increased risk of statin-induced myopathy. Simvastatin 80 mg is only to be used in patients previously on this dose for 1 year or more without evidence of myopathy. Simvastatin 40 mg typically results in a mean low-density lipoprotein (LDL) reduction of about 41%. Because doubling the dose of simvastatin (or any other statin) usually provides only an additional 6% reduction (often referred to as the “Rule of 6”), the pharmacist might anticipate PD requires only a modest additional LDL reduction. When talking to PD’s doctor, the pharmacist might recommend a different statin be used. Other statins that can lower LDL cholesterol to a similar degree as simvastatin 80 mg include atorvastatin (Lipitor) 40 mg or rosuvastatin (Crestor) 10 mg once daily. Alternatively, a second medication with a different mechanism of action could be added.
Dr. Coleman is associate professor of pharmacy practice and director of the pharmacoeconomics and outcomes studies group at the University of Connecticut School of Pharmacy. Mr. Perugini is a PharmD candidate from the University of Connecticut School of Pharmacy.