Tailoring treatment: patients with kidney disease

Last updated: Tuesday, June 20, 2017

Question
You’re asked by a doctor on your general medical ward about a patient with cellulitis. She has been advised to use oral clarithromycin as the patient is penicillin-allergic. However the patient has chronic, stable kidney disease and the doctor wants to know the correct dose to prescribe. The hospital guidelines advise that 500mg twice daily should be used but she is concerned that this is too high. The doctor tells you that the patient has an eGFR of 24ml/min.

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Outcome
After checking your patient has no contraindications to clarithromycin, the first step you take is to calculate the creatinine clearance (CrCl) as you know that drug dosing is more reliably based upon this measure of renal function rather than eGFR. You establish that the patient is male, weighs 94kg, is 68 years old, their creatinine is 230 micromols/L and that they are approximately 6 feet tall. Using the Cockcroft Gault formula you establish that their CrCl is 29.9 ml/min and so their drug clearance may be better than their eGFR would suggest. You decide to check the SPC for clarithromycin first and this states that the dose should be reduced by half when the CrCl is less than 30ml/min. However the Renal Drug Database states that for patients with a CrCl between 10 and 30 ml/min 250 to 500mg may be given twice daily.

Therefore since your patient’s CrCl is at the ‘cut-off’ for dose adjustment according to the SPC, you advise the doctor to use 500mg twice daily orally. However if the patient’s renal function deteriorates then she should consider reducing the dose.