Case Studies (November 2015)

CASE 1

LH, a 45-year-old woman, presents to your pharmacy inquiring about sunscreen choices. LH has fair skin and states, “I burn very easily, but once I get a base tan, I am fine for the rest of the summer.” LH has no known drug allergies and is not currently taking any medications.

What would be an appropriate sunscreen recommendation for LH?

CASE 2

JP is a 72-year-old man who presents to your pharmacy with a prescription for 1 tablet of sulfamethoxazole/trimethoprim (TMP/SMX) 800/160 mg orally twice daily for 7 days. JP tells you he has not been feeling well lately, so he visited his primary care physician, who gave him a diagnosis of a moderate sinus infection. Upon review of JP’s records, you see he is currently taking metformin and lisinopril. JP has type 2 diabetes and, due to many years of uncontrolled hyperglycemia, has also been given a diagnosis of renal insufficiency.

What concerns might you have regarding JP’s use of TMP/ SMX?

ANSWERS

Case 1: It is important to educate patients that any sign of a tan is evidence of skin damage; having a “base tan” does not prevent against further damage. Tanning or burning is normally a result of UV-B rays, although UV-A and UV-B rays contribute to skin cancer formation. When choosing a sunscreen, you should always recommend broad-spectrum sunscreens, which indicates both UV-A and UV-B ray protection. There are 2 types of sunscreen to choose from: physical sunscreens, such as titanium dioxide or zinc oxide, and chemical sunscreens. Physical sunscreens stay on top of the skin and reflect, scatter, and absorb UV-A and UV-B rays; they are often the best option for children and patients with sensitive skin. Chemical sunscreens are absorbed into the skin and convert UV-A and/or UV-B rays into heat. SPF is another important factor to consider when selecting an appropriate sunscreen for LH. SPF is only a measure of UV-B protection, and doubling the SPF does not double the protection. An SPF rating of 15 blocks 93% of UV-B rays, whereas SPFs 30 and 50 block 97% and 98% of UV-B rays, respectively. As the pharmacist, because of LH’s fair skin, a sunscreen with at least an SPF of 30 should be recommended. Also make sure the product is labeled “broad spectrum,” to protect LH from both UV-A and UV-B rays.

Case 2: Trimethoprim is excreted through the kidneys, and by reducing urinary excretion of potassium, it can often lead to hyperkalemia. Recent study results show that up to 6% of patients taking TMP/SMX develop hyperkalemia and that the risk increases when patients are on other medications that increase potassium, such as angiotensin-convertingenzyme inhibitors, angiotensin 2 receptor blockers, and aldosterone antagonists (eg., spironolactone). It is advisable to avoid the use of TMP/ SMX in patients at high risk for hyperkalemia due to the following factors: being older than 65 years; having renal insufficiency, diabetes, or heart failure; or taking other medications that cause potassium retention. As JP has many of the above stated risk factors, putting him at high risk of developing hyperkalemia, TMP/SMX is not the best choice to treat his sinus infection. The pharmacist might recommend amoxicillin/clavulanate (Augmentin) 875 mg/125 mg by mouth twice daily for 5 to 7 days as an alternative to treat JP’s sinus infection.

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Dr. Caranfa is Pharmacy Manager and Executive Team Lead at Target Pharmacy. Dr. Kohn is assistant professor at University of Saint Joseph School of Pharmacy, Hartford, Connecticut. Dr. Coleman is a professor at University of Connecticut School of Pharmacy, Storrs, Connecticut.

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