Diabetes medicine mbbs
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I now have substantial content from both Katzung Pharmacology and Goldman-Cecil Medicine. Let me compile a comprehensive MBBS-level answer on Diabetes Medicine.
Diabetes Mellitus — MBBS Complete Notes
1. Definition & Classification
Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from absent or inadequate pancreatic insulin secretion, with or without impairment of insulin action, leading to disturbances in carbohydrate, fat, and protein metabolism.
— Katzung's Basic and Clinical Pharmacology, 16e | Goldman-Cecil Medicine
Classification (ADA)
| Type 1 DM | Type 2 DM | |
|---|---|---|
| Age at onset | Childhood/early adulthood (any age) | Middle age / older (increasingly in obese youth) |
| Mechanism | Autoimmune β-cell destruction → absolute insulin deficiency | Insulin resistance + relative insulin deficiency |
| Genetics | Sporadic, multifactorial (HLA linkage) | Strong polygenic; 90% of all DM |
| Insulin requirement | Universal (mandatory) | Variable |
| Ketoacidosis | Common | Rare |
| Associated conditions | Autoimmunity, thyroid disorders | Obesity, HTN, dyslipidemia, PCOS |
Other types: Pancreatitis/pancreatectomy, drug-induced, MODY, LADA
Gestational DM (GDM): Glucose intolerance first detected in pregnancy (~7–10% of pregnancies)
Gestational DM (GDM): Glucose intolerance first detected in pregnancy (~7–10% of pregnancies)
2. Diagnostic Criteria (ADA)
| Test | Diabetes | Pre-diabetes (IFG/IGT) |
|---|---|---|
| Fasting plasma glucose | ≥ 126 mg/dL (7.0 mmol/L) | 100–125 mg/dL |
| 2-h OGTT (75 g) | ≥ 200 mg/dL (11.1 mmol/L) | 140–199 mg/dL |
| HbA1c | ≥ 6.5% (48 mmol/mol) | 5.7–6.4% |
| Random glucose + symptoms | ≥ 200 mg/dL | — |
In asymptomatic patients, two abnormal tests on separate occasions are required.
3. Pharmacology of Anti-Diabetic Drugs
A. INSULIN
Types of Insulin
| Type | Onset | Peak | Duration | Examples |
|---|---|---|---|---|
| Rapid-acting | 5–15 min | 1–2 h | 3–5 h | Lispro, Aspart, Glulisine |
| Short-acting | 30–60 min | 2–4 h | 5–8 h | Regular (soluble) insulin |
| Intermediate-acting | 1–3 h | 4–10 h | 12–18 h | NPH (Isophane) |
| Long-acting | 1–4 h | Peakless | 20–24 h | Glargine, Detemir |
| Ultra-long-acting | — | Flat | ~42 h | Degludec |
Mechanism
Insulin binds the insulin receptor (tyrosine kinase) → activates IRS-1 → GLUT-4 translocation to cell surface → glucose uptake in muscle and adipose tissue.
Indications
- All Type 1 DM (mandatory)
- Type 2 DM failing oral agents
- GDM not controlled by diet
- DKA, HHS, surgery, pregnancy
Complications of Insulin Therapy
- Hypoglycemia (most important/common)
- Weight gain
- Lipodystrophy (rotate injection sites)
- Somogyi effect (rebound hyperglycemia from nocturnal hypoglycemia)
- Dawn phenomenon (early morning hyperglycemia from GH/cortisol surges)
- Insulin allergy (rare with human insulin)
B. ORAL ANTI-DIABETIC DRUGS (OADs)
1. Biguanides — Metformin ⭐ (First-line for Type 2 DM)
| Feature | Detail |
|---|---|
| Mechanism | ↓ Hepatic glucose production (gluconeogenesis); ↑ peripheral insulin sensitivity; activates AMPK |
| Route | Oral; not metabolized — excreted unchanged by kidneys |
| Advantages | No hypoglycemia (doesn't stimulate insulin), weight neutral/loss, ↓ CVD events (UKPDS) |
| Contraindications | eGFR < 30 mL/min, hepatic failure, alcohol abuse, IV contrast (hold temporarily), hypoxic states |
| ADR | Lactic acidosis (rare but serious), GI upset (nausea, diarrhea — take with food), Vit B12 deficiency (long-term) |
2. Sulfonylureas — Glibenclamide (Glyburide), Glipizide, Glimepiride, Glipizide
| Feature | Detail |
|---|---|
| Mechanism | Block ATP-sensitive K⁺ channels on β-cells → depolarization → Ca²⁺ influx → insulin release |
| Generations | 1st gen: Tolbutamide, Chlorpropamide; 2nd gen: Glibenclamide, Glipizide; 3rd gen: Glimepiride |
| ADR | Hypoglycemia (major), weight gain, disulfiram-like reaction (Chlorpropamide), dilutional hyponatremia (SIADH) |
| Contraindications | Renal/hepatic failure, pregnancy, sulfa allergy |
3. Meglitinides (Glinides) — Repaglinide, Nateglinide
- Similar mechanism to sulfonylureas but shorter acting → close to meals ("prandial glucose regulators")
- Lower hypoglycemia risk than sulfonylureas
- ADR: Hypoglycemia, weight gain
4. Thiazolidinediones (TZDs / Glitazones) — Pioglitazone, Rosiglitazone
| Feature | Detail |
|---|---|
| Mechanism | Activate PPARγ (peroxisome proliferator-activated receptor gamma) → ↑ insulin sensitivity in adipose tissue and muscle |
| Advantages | No hypoglycemia; ↑ HDL, ↓ TG (Pioglitazone) |
| ADR | Fluid retention/edema, weight gain, CHF exacerbation, osteoporosis/fractures, ↑ bladder cancer risk (Pioglitazone) |
| Rosiglitazone | Withdrawn from many markets due to ↑ MI risk |
| Contraindications | Heart failure (NYHA III–IV), liver disease, osteoporosis |
5. Alpha-Glucosidase Inhibitors — Acarbose, Miglitol, Voglibose
| Feature | Detail |
|---|---|
| Mechanism | Inhibit intestinal α-glucosidase → delay carbohydrate digestion → blunt postprandial glucose rise |
| Advantages | No hypoglycemia (monotherapy), weight neutral |
| ADR | Flatulence, bloating, diarrhea (major limiting side effect) |
| Note | If hypoglycemia occurs (combination therapy), treat with glucose (not sucrose) |
6. DPP-4 Inhibitors (Gliptins) — Sitagliptin, Saxagliptin, Vildagliptin, Alogliptin, Linagliptin
| Feature | Detail |
|---|---|
| Mechanism | Inhibit dipeptidyl peptidase-4 → ↑ GLP-1 & GIP levels → ↑ glucose-dependent insulin release, ↓ glucagon |
| Advantages | No hypoglycemia, weight neutral, well-tolerated, renal dose adjustment (except Linagliptin) |
| ADR | Nasopharyngitis, pancreatitis (rare), joint pain, urticaria, Saxagliptin → ↑ HF hospitalization |
7. GLP-1 Receptor Agonists — Liraglutide, Semaglutide, Exenatide, Dulaglutide, Lixisenatide
| Feature | Detail |
|---|---|
| Mechanism | Mimic GLP-1 → ↑ glucose-dependent insulin, ↓ glucagon, ↓ gastric emptying, ↑ satiety |
| Administration | Subcutaneous injection (Oral semaglutide also available) |
| Advantages | Weight loss (significant), ↓ MACE in CVD patients (Liraglutide LEADER trial, Semaglutide SUSTAIN-6) |
| ADR | Nausea, vomiting, diarrhea, pancreatitis, thyroid C-cell tumors (contraindicated in MEN2/medullary thyroid CA) |
| Key mnemonics | "GLP-1 = Gut-Liver-Pancreas" effects |
8. SGLT-2 Inhibitors (Gliflozins) — Dapagliflozin, Empagliflozin, Canagliflozin, Ertugliflozin
| Feature | Detail |
|---|---|
| Mechanism | Inhibit sodium-glucose cotransporter-2 in proximal renal tubule → glycosuria |
| Advantages | Weight loss, BP reduction, ↓ HF hospitalizations (Empagliflozin/Dapagliflozin), ↓ CKD progression |
| ADR | Genital mycotic infections (candidiasis), UTI, DKA (euglycemic), dehydration/hypotension, Fournier's gangrene (rare) |
| Contraindications | eGFR < 30–45, recurrent UTI, type 1 DM (relative) |
4. Drug Choice by Situation
| Situation | Preferred Drug(s) |
|---|---|
| Type 2 DM, first-line | Metformin |
| Obesity + T2DM | GLP-1 agonist (Semaglutide, Liraglutide) or SGLT-2 inhibitor |
| T2DM + established CVD | GLP-1 agonist or SGLT-2 inhibitor |
| T2DM + Heart failure | SGLT-2 inhibitor (Empagliflozin, Dapagliflozin) |
| T2DM + CKD | SGLT-2 inhibitor + Metformin |
| T2DM + Pregnancy | Insulin (oral agents generally avoided) |
| Postprandial hyperglycemia | Acarbose, Meglitinides, Rapid-acting insulin |
| Hypoglycemia-prone patient | DPP-4 inhibitors, GLP-1 agonists, SGLT-2 inhibitors |
| Type 1 DM | Insulin (mandatory) + Teplizumab (delay onset, stage 2) |
5. Monitoring & Targets
| Parameter | Target |
|---|---|
| HbA1c | < 7% (individualized: < 6.5% in young; < 8% in elderly/high CVD risk) |
| Fasting glucose | 80–130 mg/dL |
| 2-h postprandial | < 180 mg/dL |
| BP | < 130/80 mmHg |
| LDL | < 70 mg/dL (with CVD); < 100 mg/dL |
6. Acute Complications
| Complication | Type 1 DM | Type 2 DM |
|---|---|---|
| DKA (Diabetic Ketoacidosis) | Common | Rare (euglycemic DKA with SGLT-2i) |
| HHS (Hyperosmolar Hyperglycemic State) | Rare | Common in elderly |
| Hypoglycemia | Common with insulin/SU | Common with SU/insulin |
DKA vs HHS
| DKA | HHS | |
|---|---|---|
| Glucose | 200–500 mg/dL | > 600 mg/dL |
| pH | < 7.3 | Normal |
| Ketones | +++ | Absent/trace |
| Osmolality | Normal/mildly ↑ | > 320 mOsm/kg |
| Mortality | 1–5% | 10–20% |
7. Chronic Complications (Mnemonic: "RENKM")
| Complication | Details |
|---|---|
| Retinopathy | Background → Proliferative; leading cause of blindness in working-age adults |
| End-stage renal disease | Kimmelstiel-Wilson nodules (nodular glomerulosclerosis); microalbuminuria → proteinuria |
| Neuropathy | Peripheral sensorimotor, autonomic (gastroparesis, orthostatic hypotension, erectile dysfunction) |
| Kardiovascular (Cardiac) | #1 cause of death; accelerated atherosclerosis, MI, stroke |
| Macrovascular + peripheral vascular disease | Claudication, gangrene, Charcot foot |
8. Key High-Yield Points for MBBS Exams
- Metformin = drug of choice for Type 2 DM; causes lactic acidosis (rare), NOT hypoglycemia
- Sulfonylureas = most common cause of hypoglycemia among OADs
- Acarbose → if hypoglycemia occurs on combination, give glucose (not table sugar)
- Pioglitazone → contraindicated in heart failure and bladder cancer
- GLP-1 agonists → contraindicated in personal/family history of medullary thyroid carcinoma / MEN2
- SGLT-2 inhibitors → can cause euglycemic DKA; genital infections common
- Dawn phenomenon = early morning hyperglycemia (physiological cortisol/GH); managed by bedtime long-acting insulin
- Somogyi effect = nocturnal hypoglycemia → rebound morning hyperglycemia; managed by reducing evening insulin dose
- Insulin is the only drug safe in pregnancy for glycemic control
- Teplizumab (anti-CD3 antibody) = first approved drug to delay onset of Type 1 DM
Sources: Katzung's Basic and Clinical Pharmacology, 16th Edition | Goldman-Cecil Medicine, International Edition
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