DRUGS AFFECTING GLUCOSE ABSORPTION AND REABSORPTION

The Front Door Bouncers (The Gut)

They control the sugar trying to enter from the food you eat (Absorption).

The Back Door Bouncers (The Kidneys)

The body naturally filters sugar out into the urine, but then quickly grabs it and pulls it back into the blood. These bouncers control that back door (Reabsorption).

Drugs Affecting ABSORPTION (The Front Door Blockers)

alpha-Glucosidase Inhibitors (Acarbose and Miglitol.)

• Normally, when you eat complex carbs (like bread or pasta), an enzyme in your small intestine called Alpha-Glucosidase acts like a pair of scissors, chopping those big carbs into tiny, absorbable single sugars (glucose).

Acarbose and Miglitol

• Mechanism of Action (MOA): These drugs hide the scissors. By inhibiting the alpha-glucosidase enzyme, the complex carbs cannot be broken down. Because they are too big to be absorbed, they stay in the gut and are eventually pooped out.

• Clinical Use: Like the Meglitinides we discussed earlier, these are strictly used to control Postprandial Glucose (the sudden spike in blood sugar right after eating a meal). You must take them with the first bite of food.

Acarbose and Miglitol: High-Yield Board Pearls & Toxicities

The GI Nightmare

The Hypoglycemia Trap (CRITICAL EXAM PEARL)

GI Nightmare

Because the undigested carbs sit in the gut, the natural bacteria in your intestines start eating them, producing massive amounts of gas. The main side effects are severe flatulence, bloating, cramps, and diarrhea.

Hypoglycemia Trap

These drugs do not cause hypoglycemia on their own. However, if a patient is taking Acarbose plus insulin or a secretagogue and their blood sugar crashes, you cannot give them table sugar, candy, or regular juice to fix it. Table sugar is sucrose (a complex carb), and Acarbose will block it from being absorbed! You MUST give them pure oral glucose (dextrose tabs/gel) or IV dextrose.

Drugs Affecting REABSORPTION (The Back Door Blockers)

Class: SGLT2 Inhibitors (The "-gliflozins") Canagliflozin, Dapagliflozin, Empagliflozin. (Suffix: "-gliflozin" — think "glucose flowin'" out of the urine).

These are some of the absolute hottest drugs in pharmacy right now because of their massive cardiovascular and renal benefits.

Normally, your kidneys filter glucose out of your blood, but a transporter called SGLT2 (Sodium-Glucose Co-Transporter 2) in the proximal tubule of the kidney grabs 90% of that sugar and throws it right back into the bloodstream.

SGLT2 Inhibitors

• Mechanism of Action (MOA): They block the SGLT2 transporter. The kidneys can no longer reabsorb the filtered glucose, so the patient literally urinates out massive amounts of sugar (up to 100 grams a day!).

• The Massive Benefits (Why doctors love them): * Urinating out sugar means urinating out calories → Weight Loss

Sugar pulls water and sodium out with it (osmotic diuresis) → Lowers Blood Pressure.

They have proven, powerful benefits in slowing down Heart Failure and Chronic Kidney Disease (CKD) progression.

Genitourinary Infections

Because the urine is completely saturated with sugar, it becomes an all-you-can-eat buffet for bacteria and fungi. Patients get highly frequent UTIs and severe vaginal yeast infections (vulvovaginal candidiasis).

Fournier's Gangrene

A rare but highly tested, life-threatening necrotizing infection (flesh-eating bacteria) of the perineum/genit*ls.

Euglycemic DKA

They can cause Diabetic Ketoacidosis (DKA) even when the patient's blood sugar looks perfectly normal (euglycemic).

The Canagliflozin Black Box Warning

Historically highly tested for causing an increased risk of bone fractures and lower limb amputations (especially toes).

Renal Cutoff

Because they work by forcing the kidneys to filter out sugar, they are practically useless for blood sugar control if the patient's kidneys are failing (eGFR < 30).

alpha-Glucosidase Inhibitors (Acarbose)

Location of Action: Small Intestine (Blocks absorption)

Effect on Weight: Weight neutral

Major Side Effects: Flatulence, diarrhea, GI cramps

Ultimate Board Pearl: Treat hypoglycemia with pure glucose only, never sucrose.

SGLT2 Inhibitors ("-gliflozins")

Location of Action: Kidneys - Proximal Tubule (Blocks reabsorption)

Effect on Weight: Promotes Weight Loss

Major Side Effects: UTIs, Yeast infections, Dehydration/Hypotension

Ultimate Board Pearl: Causes urine to test positive for glucose (this is normal for the drug, not a sign of uncontrolled diabetes!)