As a clinical pharmacist, you will get alerts about kidney problems when clarithromycin is combined with a calcium channel blocker (amlodipine, etc). Do your part...
Clarithromycin is a strong 3A4 inhibitor that can slow the metabolism of calcium channel blockers and increase their levels. This can lead to hypotension, edema, bradycardia and acute kidney injury due to reduced perfusion. One more patient over 65 seems to be hospitalized for acute kidney injury for every 465 patients on a calcium channel blocker plus clarithromycin instead of azithromycin. The risk of an interaction with clarithromycin is highest with the dihydropyridines, especially nifedipine (Adalat) or felodipine (Plendil).
Prescribe azithromycin (Zithromax) or another antibiotic, instead of clarithromycin or erythromycin, for patients on a calcium channel blocker, especially if they're over 65. If clarithromycin is needed, such as for H. pylori, consider holding the calcium channel blocker or lowering its dose. Or have patients monitor their blood pressure and report dizziness or edema.
REFERENCES
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Gandhi S, Fleet JL, Bailey DG, McArthur E, Wald R, Rehman F, Garg AX. Calcium-channel blocker-clarithromycin drug interactions and acute kidney injury. JAMA. 2013 Dec 18;310(23):2544-53. Available at: https://jamanetwork.com/journals/jama/fullarticle/1769739
Wright AJ, Gomes T, Mamdani MM, Horn JR, Juurlink DN. The risk of hypotension following co-prescription of macrolide antibiotics and calcium-channel blockers. CMAJ. 2011 Feb 22;183(3):303-7. Available at: https://www.cmaj.ca/content/183/3/303