Farxiga and Rosuvastatin Interaction

Why These Two Drugs Are Prescribed Together

Patients with type 2 diabetes frequently carry concurrent dyslipidemia, making the pairing of an SGLT2 inhibitor with a statin a routine clinical decision. Dapagliflozin addresses glycemic control, heart failure risk, and chronic kidney disease progression, while rosuvastatin targets LDL cholesterol and atherosclerotic cardiovascular disease risk.

The 2024 American Diabetes Association (ADA) Standards of Care recommend statin therapy for nearly all adults with type 2 diabetes aged 40 to 75, regardless of baseline LDL level [1]. The same guidelines endorse SGLT2 inhibitors as preferred add-on therapy for patients with established atherosclerotic cardiovascular disease (ASCVD), heart failure, or chronic kidney disease (CKD) [1]. This creates a large patient population receiving both drugs simultaneously.

In DECLARE-TIMI 58 (N=17,160), the cardiovascular outcomes trial for dapagliflozin, 75% of enrolled participants were on background statin therapy at baseline [2]. The trial demonstrated that dapagliflozin reduced hospitalization for heart failure by 27% (HR 0.73 to 95% CI 0.61 to 0.88) compared to placebo, with no signal of adverse interaction in the statin-treated subgroup [2]. This real-world co-prescribing pattern provides a substantial safety dataset.

Pharmacokinetic Profile: No Metabolic Overlap

The reason these two drugs coexist without conflict comes down to their metabolic pathways. They simply do not compete for the same enzymes or transporters.

Dapagliflozin undergoes phase II metabolism via uridine diphosphate-glucuronosyltransferase 1A9 (UGT1A9), producing an inactive 3-O-glucuronide metabolite [3]. It has negligible interaction with cytochrome P450 enzymes. The FDA-approved prescribing information for Farxiga states that dapagliflozin is "not an inhibitor of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, or CYP2E1" and is "not an inducer of CYP1A2, CYP2B6, or CYP3A4" [3]. It is a weak P-glycoprotein (P-gp) substrate but does not inhibit P-gp at therapeutic concentrations.

Rosuvastatin, by contrast, is one of the least CYP-dependent statins. Approximately 10% of its metabolism involves CYP2C9, with the remainder eliminated unchanged in feces [4]. Its clinically relevant transport interactions involve organic anion-transporting polypeptides OATP1B1 and OATP1B3 (hepatic uptake) and breast cancer resistance protein BCRP (intestinal and hepatic efflux) [4]. Drugs that inhibit these transporters (cyclosporine, certain protease inhibitors, gemfibrozil) can raise rosuvastatin plasma levels significantly [4]. Dapagliflozin does not inhibit any of these transporters.

Because UGT1A9 and OATP1B1/BCRP represent entirely separate biochemical systems, the two drugs pass through the body without altering each other's absorption, distribution, metabolism, or excretion.

What the FDA Labels Say

Both FDA-approved labels are clear on this point. The Farxiga label does not list rosuvastatin (or any statin) among drugs requiring dose modification or avoidance [3]. The label's dedicated drug interaction section tested dapagliflozin co-administration with metformin, pioglitazone, sitagliptin, glimepiride, voglibose, hydrochlorothiazide, bumetanide, valsartan, and simvastatin. In the simvastatin co-administration study, dapagliflozin did not meaningfully alter simvastatin AUC or Cmax [3].

The Crestor (rosuvastatin) label lists specific interacting drugs: cyclosporine (7.1-fold AUC increase), atazanavir/ritonavir (3.1-fold), simeprevir (2.8-fold), and gemfibrozil (1.9-fold) [4]. SGLT2 inhibitors do not appear on this list. The label recommends dose capping at 5 mg daily only when combined with cyclosporine, and at 10 mg daily with certain HIV protease inhibitors [4].

Dr. Darren McGuire, a cardiologist at UT Southwestern and DECLARE-TIMI 58 steering committee member, noted in a 2019 commentary: "The metabolic independence of SGLT2 inhibitors from CYP-mediated pathways makes them attractive additions to regimens already containing statins, antihypertensives, and antiplatelet agents" [5].

Clinical Trial Evidence for the Combination

Large randomized trials have enrolled thousands of patients taking both drugs simultaneously, providing indirect but substantial evidence of safety.

DAPA-HF (N=4,744): This heart failure with reduced ejection fraction (HFrEF) trial reported that 1,445 participants (roughly 39.5% of the dapagliflozin arm) were on concurrent statin therapy [6]. The primary composite endpoint (worsening heart failure or cardiovascular death) was reduced by 26% with dapagliflozin (HR 0.74 to 95% CI 0.65 to 0.85, P<0.001) [6]. No increased adverse event signal emerged in the statin subgroup compared to non-statin users.

DAPA-CKD (N=4,304): Among patients with CKD (eGFR 25 to 75 mL/min/1.73 m²), approximately 45% were on background statin therapy [7]. Dapagliflozin reduced the primary composite endpoint by 39% (HR 0.61 to 95% CI 0.51 to 0.72, P<0.001) regardless of statin co-administration [7]. Adverse event rates, including acute kidney injury and diabetic ketoacidosis, did not differ between statin users and non-users in the dapagliflozin arm.

DELIVER (N=6,263): In the HFpEF trial, over 50% of participants received statin therapy [8]. The treatment effect of dapagliflozin (18% reduction in composite of worsening HF or CV death) was consistent across statin subgroups [8].

The 2022 AHA/ACC/HFSA heart failure guideline explicitly recommends SGLT2 inhibitors across the spectrum of ejection fraction, and the guideline committee did not flag statin co-administration as a concern [9].

Monitoring When Taking Both Drugs

No interaction-specific monitoring is required. Standard drug-class monitoring applies to each agent independently.

For rosuvastatin: Check a fasting lipid panel 4 to 12 weeks after initiation or dose change, then annually [10]. Measure hepatic transaminases (ALT) at baseline. If a patient reports unexplained muscle pain, weakness, or tenderness, obtain a creatine kinase (CK) level. Rosuvastatin-associated myopathy occurs in approximately 0.1% of patients, and rhabdomyolysis in fewer than 0.01% [4]. Risk increases with renal impairment (dose cap of 10 mg when eGFR <30 mL/min/1.73 m²), older age, hypothyroidism, and concomitant use of actual interacting drugs like fibrates or niacin.

For dapagliflozin: Monitor renal function (eGFR and serum creatinine) before initiation and periodically thereafter [3]. Watch for signs of volume depletion, especially in patients on diuretics or with eGFR <60. Screen for genital mycotic infections, which occur in 5% to 7% of women and 2% to 3% of men on SGLT2 inhibitors [3]. Monitor for euglycemic diabetic ketoacidosis (eDKA), particularly during illness, surgery, or reduced caloric intake.

A practical checklist for the prescribing clinician:

• Baseline: eGFR, fasting lipids, ALT, HbA1c, blood pressure
• 4 to 12 weeks: repeat fasting lipids, eGFR
• Ongoing: annual lipid panel, semiannual eGFR, HbA1c every 3 to 6 months
• As needed: CK if myalgia develops, ketone assessment if eDKA suspected

Drugs That Actually Do Interact with Each of These Medications

Understanding what does interact helps clarify why this particular combination does not.

Rosuvastatin's significant interactions: Cyclosporine increases rosuvastatin AUC 7.1-fold, requiring a 5 mg dose cap [4]. Lopinavir/ritonavir raises AUC 2.1-fold [4]. Gemfibrozil increases AUC 1.9-fold, and the combination raises myopathy risk [4]. Regorafenib, a BCRP inhibitor used in oncology, can double rosuvastatin exposure [4]. Warfarin's INR may increase modestly when rosuvastatin is added.

Dapagliflozin's notable interactions: Insulin and sulfonylureas increase hypoglycemia risk when combined with dapagliflozin. The Farxiga label recommends considering a lower dose of insulin or sulfonylurea when adding dapagliflozin [3]. Loop and thiazide diuretics may amplify volume depletion and hypotension risk. Lithium levels may decrease due to the osmotic diuretic effect of SGLT2 inhibition, though clinical data are limited.

Dr. Silvio Inzucchi, director of the Yale Diabetes Center, stated in a 2020 review: "SGLT2 inhibitors carry a remarkably clean drug-interaction profile. Their UGT-based metabolism sidesteps the CYP system entirely, which is where most polypharmacy headaches originate" [11].

Special Populations: Renal Impairment, Elderly, and Heart Failure

Renal function affects both drugs differently. Rosuvastatin exposure rises with declining eGFR. At eGFR <30 mL/min/1.73 m², the starting dose should be 5 mg with a maximum of 10 mg [4]. Dapagliflozin's glycemic efficacy diminishes below eGFR 45, but its cardiorenal benefits persist down to eGFR 25 based on DAPA-CKD data [7]. The FDA removed the eGFR initiation threshold for heart failure and CKD indications in 2021 [3].

Elderly patients (aged 65 and older) may be more susceptible to rosuvastatin myopathy and dapagliflozin-related volume depletion. These are additive age-related risks, not synergistic drug-drug effects. Adequate hydration counseling and conservative initial dosing address both.

In the DAPA-HF population with a mean age of 66 years, the safety profile of dapagliflozin remained favorable regardless of statin use, background ACE inhibitor/ARB/ARNI therapy, or mineralocorticoid receptor antagonist use [6]. The absence of interaction extended across a polypharmacy population averaging 7.2 concomitant medications.

Mechanism Deep Dive: Why UGT and OATP Systems Do Not Cross-React

The UGT (uridine 5'-diphospho-glucuronosyltransferase) enzyme family catalyzes glucuronidation, a phase II conjugation reaction that attaches glucuronic acid to lipophilic substrates [12]. UGT1A9, the primary enzyme for dapagliflozin, is expressed in liver and kidney tissue. Its known inhibitors include mefenamic acid, diflunisal, and probenecid. Rosuvastatin does not inhibit UGT1A9 [4].

OATP1B1 and OATP1B3, encoded by genes SLCO1B1 and SLCO1B3, are hepatocyte membrane transporters responsible for the hepatic uptake of statins, bilirubin, and certain endogenous compounds [12]. Genetic polymorphisms in SLCO1B1 (particularly the c.521T>C variant, rs4149056) are associated with up to a 2.4-fold increase in rosuvastatin AUC and elevated myopathy risk [13]. Dapagliflozin is not a substrate, inhibitor, or inducer of either OATP isoform [3].

BCRP (ABCG2) is an efflux transporter at the intestinal brush border and hepatocyte canalicular membrane. The ABCG2 c.421C>A polymorphism (rs2231142) increases rosuvastatin bioavailability by approximately 2-fold in homozygous carriers [13]. Dapagliflozin does not interact with BCRP.

The pharmacogenomic lesson is relevant: patients with SLCO1B1 or ABCG2 loss-of-function variants should have rosuvastatin dose adjustments based on genotype, not based on any co-prescribed SGLT2 inhibitor.