Acarbose
Precose (US) · Glucobay (Europe/Asia)
Acarbose Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Type 2 diabetes mellitus — glycemic control | Adults | Adjunctive to diet & exercise; monotherapy or combination with SFU, metformin, or insulin | FDA Approved |
Acarbose was the first alpha-glucosidase inhibitor approved in the United States (September 1995). It lowers postprandial blood glucose by delaying carbohydrate digestion in the small intestine. Its effect on glycemic control is additive when combined with sulfonylureas, metformin, or insulin, and it diminishes the insulinotropic and weight-increasing effects of sulfonylureas. Acarbose is not a substitute for insulin and is not indicated for type 1 diabetes or diabetic ketoacidosis. There is no conclusive evidence of macrovascular risk reduction with acarbose.
Prevention of type 2 diabetes in impaired glucose tolerance (IGT): The STOP-NIDDM trial demonstrated a 25% relative risk reduction in progression from IGT to T2DM with acarbose 100 mg TID over 3.3 years. Evidence quality: High (multicentre RCT). The ADA lists acarbose as an option for diabetes prevention in at-risk individuals.
Postprandial hypoglycemia (dumping syndrome): Used in some centres for reactive hypoglycemia after bariatric surgery. Evidence quality: Low (case series, expert opinion).
Acarbose Dosing
Adults with Type 2 Diabetes
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| T2DM — monotherapy or add-on to diet/exercise | 25 mg PO TID | 50–100 mg PO TID | 100 mg TID (>60 kg) 50 mg TID (≤60 kg) | Take with first bite of each meal; can start once daily to limit GI effects Titrate every 4–8 weeks using 1-hour postprandial glucose or HbA1c |
| T2DM — add-on to sulfonylurea | 25 mg PO TID | 50–100 mg PO TID | 100 mg TID | Increased hypoglycemia risk; use oral glucose (dextrose) for treatment, not sucrose Acarbose blocks sucrose hydrolysis — sucrose will not correct hypoglycemia rapidly |
| T2DM — add-on to metformin | 25 mg PO TID | 50–100 mg PO TID | 100 mg TID | No increased hypoglycemia risk with metformin alone; additive glycemic benefit Placebo-subtracted HbA1c reduction of −0.65% in PI Study 3 |
| T2DM — add-on to insulin | 25 mg PO TID | 50–100 mg PO TID | 100 mg TID | May increase hypoglycemia risk; use oral glucose (dextrose) for rescue Placebo-subtracted HbA1c reduction of −0.69% in PI Study 4 |
This is the most critical counselling point for acarbose. Because acarbose inhibits the breakdown of sucrose (table sugar) to glucose, patients must carry oral glucose tablets (dextrose) for hypoglycemia rescue when on concomitant insulin or sulfonylureas. Sucrose, fruit juice with sucrose, or candy will not be rapidly absorbed while acarbose is active. Severe hypoglycemia may require IV glucose or glucagon injection.
In fixed-dose monotherapy trials, placebo-subtracted HbA1c reductions were: 25 mg TID −0.44%, 50 mg TID −0.77%, 100 mg TID −0.74% (FDA PI Table 1). There was no statistically significant difference between 50 mg and 100 mg TID. Acarbose primarily reduces postprandial glucose (1-hour reduction of 34–74 mg/dL above placebo across clinical studies) with a more modest effect on fasting glucose.
Pharmacology of Acarbose
Mechanism of Action
Acarbose is a complex oligosaccharide derived from fermentation of the microorganism Actinoplanes utahensis. It acts as a competitive, reversible inhibitor of two key carbohydrate-digesting enzyme systems: pancreatic alpha-amylase (which hydrolyzes complex starches to oligosaccharides in the intestinal lumen) and membrane-bound intestinal alpha-glucosidase enzymes (which further break down oligosaccharides, trisaccharides, and disaccharides to absorbable monosaccharides at the brush border of the small intestine). By delaying the enzymatic cleavage of dietary carbohydrates, acarbose slows glucose absorption and attenuates the postprandial rise in blood glucose. Notably, acarbose does not enhance insulin secretion, does not inhibit lactase, and therefore does not induce lactose intolerance. Its mechanism is entirely distinct from sulfonylureas, metformin, or insulin, making its glycemic effect additive in combination therapy.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | <2% of oral dose absorbed as active drug; ~35% of total radioactivity absorbed (as metabolites); Tmax ~1 h (active drug), 14–24 h (metabolites) | Very low systemic bioavailability is therapeutically desired; acarbose acts locally in the GI tract |
| Distribution | Not clinically significant due to minimal systemic absorption | Systemic distribution is negligible; the drug exerts its pharmacological effect within the intestinal lumen and brush border |
| Metabolism | Exclusively within GI tract by intestinal bacteria and digestive enzymes; ≥13 metabolites identified; no CYP involvement | No hepatic first-pass metabolism in the traditional sense; no CYP-mediated drug interactions |
| Elimination | 51% excreted in feces (unabsorbed); <2% in urine as active drug; ~34% of dose absorbed as metabolites and excreted renally; t½ ~2 h | No drug accumulation with TID dosing; in severe renal impairment (CrCl <25 mL/min), plasma concentrations of absorbed drug are ~5x higher — use not recommended if serum creatinine >2.0 mg/dL |
Side Effects of Acarbose
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Flatulence | 74% (vs 29% placebo) | Most common reaction; caused by bacterial fermentation of undigested carbohydrates in the colon; tends to abate over time but is the leading cause of patient dissatisfaction |
| Diarrhea | 31% (vs 12% placebo) | Dose-related; tends to return to pretreatment levels over time; worsened by non-adherence to prescribed diet or high-carbohydrate intake |
| Abdominal pain | 19% (vs 9% placebo) | Usually mild to moderate; tends to resolve with continued therapy; reduce dose if distressing despite dietary compliance |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Elevated transaminases (AST/ALT >ULN) | 14% (at doses up to 300 mg TID; similar to placebo at approved 100 mg TID dose) | Asymptomatic and reversible; more common at higher doses, in females, and in patients <60 kg; check LFTs every 3 months in first year |
| Elevated transaminases (>3x ULN) | 3% (at doses up to 300 mg TID) | Dose-related; consider dose reduction or discontinuation if persistent |
| Small reductions in hematocrit | Reported more often than placebo | Not associated with hemoglobin reductions; not clinically significant |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Hepatotoxicity (transaminases >500 IU/L) | 62 cases in ~3 million patient-years (postmarketing) | 2–8 months after initiation | Discontinue acarbose; 55/59 cases resolved on discontinuation; hepatocellular pattern; check LFTs every 3 months in year 1 |
| Fulminant hepatitis (fatal cases) | Very rare (postmarketing); causal relationship unclear | Variable | Discontinue immediately if jaundice or marked transaminase elevation develops; urgent hepatology referral |
| Pneumatosis cystoides intestinalis | Very rare (postmarketing) | Variable | Discontinue acarbose; imaging if symptoms of diarrhea, mucus discharge, rectal bleeding, or constipation develop |
| Ileus / subileus | Very rare (postmarketing) | Variable | Discontinue; surgical evaluation if signs of intestinal obstruction |
| Thrombocytopenia | Very rare (postmarketing) | Variable | Discontinue; monitor CBC; consider alternative cause |
| Reason for Discontinuation | Incidence | Context |
|---|---|---|
| Flatulence | Most frequent | Leading cause of non-adherence; severity may be reduced by gradual titration and dietary counselling to reduce gas-producing foods |
| Diarrhea | Common | Tends to improve with continued therapy and dietary compliance |
| Abdominal discomfort | Common | Temporary or permanent dose reduction may be necessary if distressing despite dietary adherence |
All GI adverse effects of acarbose are a direct manifestation of its mechanism of action: undigested carbohydrates delivered to the colon undergo bacterial fermentation, producing gas. Strict dietary adherence to the prescribed carbohydrate intake is essential. Strategies include starting at 25 mg once daily (not TID) for the first 1–2 weeks, escalating slowly every 4–8 weeks, and advising patients to avoid carbonated beverages, excessive sucrose, and gas-producing foods. In the 1-year safety study from the PI, the frequency and intensity of flatulence tended to decrease over time at stable doses.
Acarbose Drug Interactions
Acarbose has minimal systemic absorption and does not undergo CYP-mediated metabolism, resulting in a low overall drug interaction burden. Its primary interaction mechanism is through altered GI absorption kinetics of concomitant oral medications and through additive glucose-lowering effects when combined with other antidiabetic agents.
Monitoring for Acarbose
- 1-Hour Postprandial GlucoseDuring initiation and titration
RoutineThe primary tool for dose titration; use to identify the minimum effective dose. Check at each dose escalation step (every 4–8 weeks). - HbA1cEvery 3 months initially, then every 3–6 months
RoutineExpected placebo-subtracted reduction of 0.5–0.8%. Do NOT use 1,5-anhydroglucitol (1,5-AG) assay — measurements are unreliable with acarbose. - Serum Transaminases (AST/ALT)Every 3 months during year 1, then periodically
RoutineParticularly important at doses >50 mg TID. If elevated, consider dose reduction or withdrawal. In postmarketing experience, 41/62 cases of severe elevation were on ≥100 mg TID and 33/45 weighed <60 kg. Most resolved on discontinuation. - GI TolerabilityEach titration visit
RoutineAssess flatulence, diarrhea, and abdominal pain severity. Confirm dietary compliance. If intolerable despite diet adherence, reduce dose temporarily or permanently. - Blood GlucoseOngoing if on SFU or insulin
Trigger-basedAcarbose alone does not cause hypoglycemia. Monitor when combined with SFU or insulin. Ensure patient has oral glucose (dextrose) available — not sucrose. - Renal FunctionBaseline
RoutineNot recommended if serum creatinine >2.0 mg/dL. In severe renal impairment (CrCl <25 mL/min), plasma concentrations are ~5-fold higher. No long-term data in significant renal dysfunction.
Contraindications & Cautions
Absolute Contraindications
- Known hypersensitivity to acarbose
- Diabetic ketoacidosis — acarbose is not appropriate for this acute metabolic emergency
- Cirrhosis
- Inflammatory bowel disease — includes Crohn’s disease and ulcerative colitis
- Colonic ulceration
- Partial intestinal obstruction or predisposition to obstruction — increased gas formation may worsen obstruction
- Chronic intestinal diseases with marked disorders of digestion or absorption
- Conditions that may deteriorate from increased gas formation in the intestine — includes large hernias
Relative Contraindications (Specialist Input Recommended)
- Significant renal impairment (serum creatinine >2.0 mg/dL) — plasma concentrations of absorbed acarbose are markedly elevated; not studied in long-term trials
- Patients weighing ≤60 kg — higher risk of hepatotoxicity at doses ≥100 mg TID; maximum dose should be 50 mg TID
Use with Caution
- Concomitant insulin or sulfonylureas — hypoglycemia risk increased; ensure patient carries oral glucose (dextrose), not sucrose
- Patients at risk of malnutrition — acarbose causes carbohydrate malabsorption by design; consider nutritional impact in underweight or elderly patients
- Stress situations (fever, trauma, infection, surgery) — temporary loss of glycemic control may necessitate temporary insulin therapy
In approximately 3 million patient-years of international postmarketing experience, 62 cases of serum transaminase elevations exceeding 500 IU/L were reported (29 with jaundice). Cases of fulminant hepatitis with fatal outcome have been reported, though a causal relationship to acarbose remains unclear. In 55 of 59 cases with follow-up, hepatic abnormalities improved or resolved upon discontinuation. Patients weighing less than 60 kg and those on doses of 100 mg TID or greater appear to be at higher risk. Monitor serum transaminases every 3 months during the first year of treatment and periodically thereafter.
Patient Counselling
Purpose of Therapy
Acarbose helps control blood sugar after meals by slowing down the digestion of carbohydrates (starchy and sugary foods) in the gut. This means sugar enters your bloodstream more gradually after eating, preventing sharp spikes. It is used alongside diet, exercise, and sometimes other diabetes medications to manage type 2 diabetes.
How to Take
Take acarbose with the first bite of each main meal, up to three times daily. Do not take it on an empty stomach or after finishing a meal. Swallow the tablet whole — do not crush it, as this may worsen stomach side effects. Continue following your prescribed diet; high-carbohydrate meals or deviation from dietary advice will intensify gas, bloating, and diarrhea.
Sources
- PRECOSE (acarbose tablets). Full Prescribing Information. Bayer HealthCare Pharmaceuticals. Revised March 2015. FDA LabelPrimary source for all dosing, adverse reaction incidence rates, pharmacokinetic data, contraindications, and drug interaction studies.
- Chiasson JL, Josse RG, Gomis R, et al. Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomised trial. Lancet. 2002;359(9323):2072–2077. doi:10.1016/S0140-6736(02)08905-5STOP-NIDDM (n=1,429): Acarbose 100 mg TID reduced progression from IGT to T2DM by 25% (HR 0.75) over 3.3 years. High discontinuation rate (~30%) due to GI effects.
- Chiasson JL, Josse RG, Gomis R, et al. Acarbose treatment and the risk of cardiovascular disease and hypertension in patients with impaired glucose tolerance: the STOP-NIDDM trial. JAMA. 2003;290(4):486–494. doi:10.1001/jama.290.4.486CV sub-analysis of STOP-NIDDM: 49% relative risk reduction in cardiovascular events (contested; small number of events; methodology debated).
- Holman RR, Coleman RL, Chan JCN, et al. Effects of acarbose on cardiovascular and diabetes outcomes in patients with coronary heart disease and impaired glucose tolerance (ACE): a randomised, double-blind, placebo-controlled trial. Lancet Diabetes Endocrinol. 2017;5(11):877–886. doi:10.1016/S2213-8587(17)30309-1ACE trial (n=6,522): Acarbose in CHD patients with IGT did not reduce composite CV endpoint (HR 0.98); reduced new-onset diabetes by 18%.
- Coniff RF, Shapiro JA, Seaton TB, Bray GA. Multicenter, placebo-controlled trial comparing acarbose with placebo, tolbutamide, and tolbutamide-plus-acarbose in non-insulin-dependent diabetes mellitus. Am J Med. 1995;98(5):443–451. doi:10.1016/S0002-9343(99)80343-XEarly pivotal trial demonstrating acarbose efficacy and the additive glucose-lowering effect when combined with sulfonylureas.
- American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes—2025. Diabetes Care. 2025;48(Suppl 1). doi:10.2337/dc25-SINTADA guidelines note alpha-glucosidase inhibitors as an option in pharmacotherapy; acarbose listed for diabetes prevention in IGT populations.
- Davies MJ, Aroda VR, Collins BS, et al. Management of hyperglycemia in type 2 diabetes, 2022. A consensus report by the ADA and EASD. Diabetes Care. 2022;45(11):2753–2786. doi:10.2337/dci22-0034ADA/EASD consensus including alpha-glucosidase inhibitors in the pharmacologic treatment algorithm, positioned after preferred agents.
- Van de Laar FA, Lucassen PL, Akkermans RP, et al. Alpha-glucosidase inhibitors for patients with type 2 diabetes: results from a Cochrane systematic review and meta-analysis. Diabetes Care. 2005;28(1):154–163. doi:10.2337/diacare.28.1.154Cochrane meta-analysis of alpha-glucosidase inhibitors confirming HbA1c reduction of ~0.8%, predominantly via postprandial glucose lowering; GI effects as primary limitation.
- Acarbose. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases; 2012 (updated 2020). NCBI BookshelfComprehensive review of acarbose-associated hepatotoxicity including case series, incidence estimates, and clinical patterns of liver injury.
- Acarbose. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024. NCBI BookshelfClinical pharmacology overview including dosing, pharmacokinetics, adverse effects, and interprofessional considerations.
- Moelands SV, Lucassen PL, Akkermans RP, et al. Alpha-glucosidase inhibitors for prevention or delay of type 2 diabetes mellitus and its associated complications in people at increased risk of developing type 2 diabetes mellitus. Cochrane Database Syst Rev. 2018;12:CD005061. doi:10.1002/14651858.CD005061.pub3Cochrane review of alpha-glucosidase inhibitors for diabetes prevention; confirmed diabetes risk reduction but found no conclusive evidence for mortality or macrovascular benefit.