FRCA Notes

Acarbose

Resources

  • Acarbose is an intestinal alpha-glucosidase inhibitor that reduces post-prandial hyperglycaemia
  • Its efficacy depends on carbohydrate intake, so the risk of hypoglycaemia is very low
  • It is no longer recommended in UK guidelines and is not widely used

  • The gut cannot absorb disaccharides such as sucrose
  • Alpha-glucosidase in the intestinal brush border normally cleaves disaccharides into absorbable monosaccharides
  • Acarbose is a competitive inhibitor of this enzyme, and also inhibits pancreatic alpha-amylase (which hydrolyses complex carbohydrates)

  • This delays carbohydrate absorption, limiting the rate of rise of plasma glucose and reducing total carbohydrate absorbed
  • HbA1c reduction is modest, ~8mmol/mol (0.75%)
  • Can be used with sulphonylureas, metformin or insulin

Absorption

  • Minimal systemic absorption; acts locally in the gut

Metabolism

  • Degraded within the GI tract by intestinal bacteria and digestive enzymes

Excretion

  • The small absorbed fraction is renally excreted

Gastrointestinal

  • Colonic bacteria ferment the increased carbohydrate load, causing flatulence, bloating, abdominal pain and diarrhoea
  • The dose must therefore be built up gradually
  • May raise hepatic transaminases

Nutritional and metabolic

  • Few systemic effects
  • Hypoglycaemia only occurs in combination with other agents
    • This should be treated with glucose rather than sucrose, whose digestion is inhibited

Contraindications

  • Inflammatory bowel disease or colonic ulceration
  • Intestinal obstruction, or predisposition to it
  • Previous abdominal surgery
  • Severe hepatic impairment
  • Renal impairment with eGFR <25ml/min/1.73m2

Perioperative management


  • Morning surgery: omit the morning dose if not eating
  • Afternoon surgery: take the morning dose if eating breakfast
  • Discontinue when a liver reduction diet starts before bariatric surgery

  • Low risk of hypoglycaemia when used alone; target capillary blood glucose 4-10mmol/L

  • Restart once normal enteral intake resumes
  • Its GI side-effects (flatulence, diarrhoea) may be relevant postoperatively
  • Normally discontinued in critical illness given its mode of action and its contraindications in GI, hepatic and renal disease