Pharmacodynamic Interactions: Diuretics: Canagliflozin may add to the effect of diuretics and may increase the risk of dehydration and hypotension (see Precautions).
Insulin and Insulin Secretagogues: Insulin and insulin secretagogues, such as sulphonylureas, can cause hypoglycaemia. Therefore, a lower dose of insulin or an insulin secretagogue may be required to reduce the risk of hypoglycaemia when used in combination with canagliflozin (see Dosage & Administration and Adverse Reactions).
Pharmacokinetic Interactions: Effects of other medicinal products on canagliflozin The metabolism of canagliflozin is primarily via glucuronide conjugation mediated by UDP glucuronosyl transferase 1A9 (UGT1A9) and 2B4 (UGT2B4). Canagliflozin is transported by P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP).
Enzyme inducers [such as St. John's wort (Hypericum perforatum), rifampicin, barbiturates, phenytoin, carbamazepine, ritonavir, efavirenz] may give rise to decreased exposure of canagliflozin. Following co-administration of canagliflozin with rifampicin (an inducer of various active transporters and drug-metabolising enzymes), 51% and 28% decreases in canagliflozin systemic exposure (AUC) and peak concentration (Cmax) were observed. These decreases in exposure to canagliflozin may decrease efficacy.
If a combined inducer of these UGT enzymes and transport proteins must be co-administered with canagliflozin, monitoring of glycaemic control to assess response to canagliflozin is appropriate. If an inducer of these UGT enzymes must be co-administered with canagliflozin, increasing the dose to 300 mg once daily may be considered if patients are currently tolerating canagliflozin 100 mg once daily, have an eGFR ≥60 mL/min/1.73 m2 or CrCl ≥60 mL/min, and require additional glycaemic control. In patients with an eGFR 45 mL/min/1.73 m2 to <60 mL/min/1.73 m2 or CrCl 45 mL/min to <60 mL/min taking canagliflozin 100 mg who are receiving concurrent therapy with a UGT enzyme inducer and who require additional glycaemic control, other glucose-lowering therapies should be considered (see Dosage & Administration and Precautions).
Cholestyramine may potentially reduce canagliflozin exposure. Dosing of canagliflozin should occur at least 1 hour before or 4-6 hours after administration of a bile acid sequestrant to minimise possible interference with their absorption.
Interaction studies suggest that the pharmacokinetics of canagliflozin are not altered by metformin, hydrochlorothiazide, oral contraceptives (ethinyl estradiol and levonorgestrol), ciclosporin, and/or probenecid.
Effects of Canagliflozin on Other Medicinal Products: Digoxin: The combination of canagliflozin 300 mg once daily for 7 days with a single dose of digoxin 0.5 mg followed by 0.25 mg daily for 6 days resulted in a 20% increase in AUC and a 36% increase in Cmax of digoxin, probably due to inhibition of P-gp. Canagliflozin has been observed to inhibit P-gp in vitro. Patients taking digoxin or other cardiac glycosides (e.g., digitoxin) should be monitored appropriately.
Dabigatran: The effect of concomitant administration of canagliflozin (a weak P-gp inhibitor) on dabigatran etexilate (a P-gp substrate) has not been studied. As dabigatran concentrations may be increased in the presence of canagliflozin, monitoring (looking for signs of bleeding or anaemia) should be exercised when dabigatran is combined with canagliflozin.
Simvastatin: The combination of canagliflozin 300 mg once daily for 6 days with a single dose of simvastatin (CYP3A4 substrate) 40 mg resulted in a 12% increase in AUC and a 9% increase in Cmax of simvastatin and an 18% increase in AUC and a 26% increase in Cmax of simvastatin acid. The increases in simvastatin and simvastatin acid exposures are not considered clinically relevant.
Inhibition of BCRP by canagliflozin cannot be excluded at an intestinal level and increased exposure may therefore occur for medicinal products transported by BCRP, e.g. certain statins like rosuvastatin and some anti-cancer medicinal products.
In interaction studies, canagliflozin at steady-state had no clinically relevant effect on the pharmacokinetics of metformin, oral contraceptives (ethinyl estradiol and levonorgestrol), glibenclamide, paracetamol, hydrochlorothiazide, or warfarin.
Drug/Laboratory Test Interference: 1,5-AG Assay: Increases in urinary glucose excretion with Invokana can falsely lower 1,5-anhydroglucitol (1,5-AG) levels and make measurements of 1,5-AG unreliable in assessing glycemic control. Therefore, 1,5-AG assays should not be used for assessment of glycemic control in patients on canagliflozin. For further detail, it may be advisable to contact the specific manufacturer of the 1,5-AG assay.