No clinically relevant effect on ranitidine concentrations was observed when Kaletra was coadministered with ranitidine (150 mg single dose) No dose adjustment necessary.
Kaletra Summary of Product Characteristics, AbbVie Ltd, January 2021.

Drug interaction studies reveal no clinically significant interaction between Kaletra and ranitidine. Coadministration of ranitidine (150 mg single dose) and Kaletra tablets (400/100 mg twice daily for 10 days) was studied in 12 HIV- subjects. Lopinavir Cmax, AUC and Cmin decreased by 1%, 3% and 10%, respectively. Coadministration of the same dose of ranitidine with once daily Kaletra tablets (800/200 mg once daily for 10 days) to 10 HIV- subjects resulted in decreases in lopinavir Cmax, AUC and Cmin of 3%, 5% and 18%, respectively.
Kaletra Prescribing Information, AbbVie Ltd, October 2020.

The effect of omeprazole (40 mg once daily) or ranitidine (150 mg once daily) on the lopinavir/ritonavir tablet (400/100 mg twice daily or 800/200 once daily) was assessed in HIV+ subjects. Neither omeprazole or ranitidine significantly altered lopinavir or ritonavir exposure after coadministration.
Lack of effect of acid-reducing agents on the pharmacokinetics of lopinavir/ritonavir tablet. Klein et al. 13th Conference on Retroviruses and Opportunistic Infections, Denver, February, 2006, abstract 578.

The effects of gastric acid reducing agents (proton pump inhibitors, H2 receptor antagonists or antacids) on lopinavir concentrations were assessed on 5 occasions over a 48-week period in antiretroviral naïve patients receiving lopinavir/ritonavir (400/100 mg twice daily or 800/200 mg once daily). No significant differences in lopinavir concentrations at any week were observed between patients receiving twice daily lopinavir/ritonavir alone (n=45) or with an acid reducing agent (n=7). For patients receiving once daily lopinavir/ritonavir alone (n=86) or with an acid reducing agent (n=8), no significant difference were observed, with the exception of higher lopinavir concentrations at week 24 for patients on acid reducing agents. Similar trends were observed for ritonavir. Further formal investigations of the effect of potent acid reducing agents on lopinavir/ritonavir pharmacokinetics are warranted.
Lack of effect of gastric acid reducing agents on lopinavir/ritonavir plasma concentrations in HIV-infected patients. Bertz RJ, Chiu YL, Naylor C, et al. 7th International Congress on Drug Therapy in HIV Infection, Glasgow, November 2004, abstract P279.