Coadministration has not been studied. Ascorbic acid is oxidised to dehydroascorbic acid where some is metabolised to oxalic acid and the inactive ascorbate-2-sulphate. Large doses are rapidly excreted in the urine when in excess of the requirements of the body. A pharmacokinetic interaction is unlikely with vitamin C itself. However, vitamin C can be found in multivitamin preparations. Simultaneous coadministration of a multivitamin preparation decreased dolutegravir exposure by ~33%. Dolutegravir should be administered 2 hours before or 6 hours after medications containing polyvalent cations, such as multivitamin preparations. Medicinal products that reduce dolutegravir exposure (e.g. multivitamins) should be avoided in the presence of integrase class resistance.

Simultaneous coadministration of calcium carbonate (1200 mg) and dolutegravir (50 mg single dose) to fasting subjects decreased dolutegravir Cmax, AUC and Cmin by 37%, 39% and 39%, respectively. Simultaneous coadministration to fed subjects increased dolutegravir Cmax, AUC and Cmin by 7%, 9% and 8%, respectively. Coadministration of calcium carbonate 2 h after dolutegravir had no effect on dolutegravir Cmax and decreased dolutegravir AUC and Cmin by 6% and 10%, respectively. Dolutegravir should be administered 2 hours before or 6 hours after taking medications containing polyvalent cations, such as calcium supplements. The US Prescribing information suggests that, alternatively, dolutegravir and calcium supplements can be taken together with food. Medicinal products that reduce dolutegravir exposure (e.g. calcium supplements) should be avoided in the presence of integrase class resistance.

Coadministration has not been studied. Large doses of ascorbic acid may cause the urine to become acidic causing unexpected renal tubular reabsorption of acidic drugs, thus producing an exaggerated response. Conversely basic drugs may exhibit decreased reabsorption resulting in a decreased therapeutic effect. Lamivudine is predominantly eliminated unchanged via active renal tubular secretion, however unless treatment with ascorbic acid involves large doses of prolonged duration, significant interactions are not expected with vitamin C when given alone or in multivitamins.

Coadministration has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely with vitamin C when given alone or in multivitamins. Ascorbic acid is oxidised to dehydroascorbic acid where some is metabolised to oxalic acid and the inactive ascorbate-2-sulphate. Large doses are rapidly excreted in the urine when in excess of the requirements of the body. There is therefore little potential for interaction with abacavir via modulation of, or competition for metabolic pathways.

Based on metabolism and clearance, a pharmacokinetic interaction is unlikely. [Dolutegravir is available coformulated with lamivudine for the treatment of HIV-1 infection where there is no known or suspected resistance to the integrase inhibitor class, or to lamivudine.]

Coadministration has not been studied but based on metabolism and clearance, a clinically significant interaction is unlikely. Ascorbic acid is oxidised to dehydroascorbic acid where some is metabolised to oxalic acid and the inactive ascorbate-2-sulphate. Large doses are rapidly excreted in the urine when in excess of the requirements of the body. There is therefore little potential for an interaction with abacavir via modulation of, or competition for metabolic pathways.

Coadministration has not been studied. Large doses of ascorbic acid may cause the urine to become acidic causing unexpected renal tubular reabsorption of acidic drugs, thus producing an exaggerated response. Conversely basic drugs may exhibit decreased reabsorption resulting in a decreased therapeutic effect. Lamivudine is predominantly eliminated unchanged via active renal tubular secretion, however unless treatment with ascorbic acid involves large doses of prolonged duration, significant interactions are not expected.

Coadministration has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely. Ascorbic acid is oxidised to dehydroascorbic acid where some is metabolised to oxalic acid and the inactive ascorbate-2-sulphate. Large doses are rapidly excreted in the urine when in excess of the requirements of the body.

No significant pharmacokinetic interaction was observed in clinical studies. A high rate of virological failure and emergence of resistance reported when lamivudine was combined with tenofovir and abacavir as a once daily regimen. Note, the bioavailability of lamivudine solution has been shown to be significantly reduced in a dose dependent manner by sorbitol which is present in liquid formulations such as abacavir oral solution.