Coadministration of clarithromycin (500 mg twice daily) and ritonavir (200 mg twice daily) increased clarithromycin AUC by 77% and Cmin by 31%. The AUC and Cmin of 14-OH clarithromycin metabolite were decreased by 100% and 99%, respectively. Due to the large therapeutic window of clarithromycin no dose reduction should be necessary in patients with normal renal function. Clarithromycin doses greater than 1 g per day should not be co-administered with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer. For patients with renal impairment, a clarithromycin dose reduction should be considered: for patients with creatinine clearance of 30 to 60 ml/min the dose should be reduced by 50%, for patients with creatinine clearance less than 30 ml/min the dose should be reduced by 75%.
Norvir Summary of Product Characteristics, AbbVie Ltd, September 2016.

The coadministration of ritonavir (200 mg every 8 hours for 4 days) with clarithromycin (500 mg every 12 hours for 4 days) was investigated in 22 subjects. Ritonavir AUC, Cmax and Cmin were increased by 12%,15% and 14%, respectively. Clarithromycin AUC and Cmax were increased by 77% and 31%, respectively, whilst Cmin increased 2.8-fold. The 14-OH clarithromycin metabolite AUC, Cmax and Cmin were reduced by 100%, 99% and 100%, respectively. No dose adjustment for patients with normal renal function is necessary. For patients with renal impairment adjust clarithromycin dose as follows: for patients with creatinine clearance 30-60 ml/min the dose of clarithromycin should be reduced by 50%; for patients with creatinine clearance <30 ml/min the dose of clarithromycin should be decreased by 75%.
Norvir Prescribing Information, AbbVie Inc, December 2016.

Coadministration of ritonavir (200 mg every 8 h) and clarithromycin (500 mg every 12 h) was studied in 22 subjects. There was a 77% increase in clarithromycin AUC and a 100% decrease in 14-OH clarithromycin AUC. There was a 31% increase in clarithromycin Cmax and a 99% decrease in 14-OH clarithromycin Cmax. Ritonavir AUC increased by 12% and Cmax by 15% in the presence of clarithromycin.
Pharmacokinetic interaction between ritonavir and clarithromycin. Ouellet D, Hsu A, Granneman GR, et al. Clin Pharmacol Ther, 1998, 64:355–62.