Clarithromycin Dosing with Creatinine 1.2
For a patient with a creatinine of 1.2 mg/dL, use the standard clarithromycin dose of 500 mg orally every 12 hours without adjustment, as dose reduction is only required when creatinine clearance falls below 30 mL/min. 1, 2
Determining Need for Dose Adjustment
A serum creatinine of 1.2 mg/dL typically corresponds to mild renal impairment and does not meet the threshold for clarithromycin dose reduction according to FDA labeling and clinical guidelines. 2
Dose adjustment is specifically indicated only when creatinine clearance is less than 30 mL/min (severe renal impairment), where the dose should be reduced by 50% or the dosing interval doubled. 1, 2
For patients with creatinine clearance of 30-60 mL/min (moderate impairment), dose adjustment is only necessary if they are taking concomitant atazanavir or ritonavir-containing regimens. 2
Standard Dosing Recommendations
The usual adult dose is 500 mg orally every 12 hours for immediate-release formulations, or 1 gram every 24 hours for extended-release tablets. 2
Treatment duration ranges from 7-14 days depending on the infection being treated. 2
Clarithromycin should be taken with food when using extended-release formulations. 2
Important Monitoring Considerations
Calculate creatinine clearance rather than relying solely on serum creatinine, especially in elderly patients, those with low muscle mass, or borderline values, as serum creatinine alone may underestimate the degree of renal impairment. 3, 4
In patients with severe renal impairment (CrCl <30 mL/min), both clarithromycin and its active metabolite (14-hydroxyclarithromycin) accumulate significantly, with increased plasma concentrations and prolonged elimination half-life. 3, 4, 5
The 14-hydroxy metabolite has antimicrobial activity equal to or superior to the parent compound, particularly against organisms like Haemophilus influenzae, making accumulation clinically relevant. 3, 6, 5
Critical Drug Interactions to Avoid
Do not use clarithromycin with drugs metabolized by CYP3A4 that have narrow therapeutic indices, including cisapride, pimozide, ergot alkaloids, lovastatin, simvastatin, lomitapide, and lurasidone, as these combinations are contraindicated. 2
Exercise caution with theophylline, as clarithromycin inhibits hepatic metabolism and can cause severe toxicity including rhabdomyolysis and acute renal failure, particularly in elderly or dehydrated patients. 7
Monitor closely if using with carbamazepine, cyclosporin, digoxin, or warfarin due to potential for significant drug level increases. 3
Common Pitfalls
Do not assume dose adjustment is needed based on creatinine 1.2 alone—this value typically does not warrant reduction unless calculated creatinine clearance is below 30 mL/min. 1, 2
Avoid abrupt discontinuation if creatinine rises during therapy; investigate other causes such as drug interactions (particularly with calcium channel blockers), volume depletion, or concurrent nephrotoxic medications before attributing changes to the antibiotic. 1
Remember that elderly patients may have significantly reduced creatinine clearance despite seemingly normal creatinine levels due to decreased muscle mass. 4, 5