Coadministration has not been studied. Roxatidine acetate is rapidly metabolised by esterases to its active metabolite roxatidine. Metabolism of roxatidine involves minimal contribution from CYP enzymes (CYP2A6 and CYP2D6). Dolutegravir is mainly metabolized by UGT1A1 and to a lesser extent by CYP3A4. Rilpivirine is metabolized by CYP3A4. Dolutegravir/rilpivirine is unlikely to affect roxatidine metabolism. Roxatidine is unlikely to affect UGT1A1 and does not inhibit or induce CYP3A4. Data from an interaction study with omeprazole suggest that solubility of dolutegravir is not influenced by changes in gastric pH. However, coadministration may reduce rilpivirine absorption due to gastric pH increase. The combination of dolutegravir/rilpivirine and H2-receptor antagonists should be used with particular caution. Only H2-receptor antagonists that can be dosed once daily should be used and should be taken at least 4 hours after or 12 hours before dolutegravir/rilpivirine.