Gastrointestinal System classification

Drugs for acid peptic disorders 
Anti-emetic drugs 
Emetics 
Laxatives 
Dehydration in diarrhoea 
Antidiarrheal agents 
Agents for irritable bowel syndrome 
Probiotics and prebiotics
Gallstone dissolving agents

Respiratory system classification

Anti-tussives
Drugs for bronchial asthma/COPD

Hormones and hormone antagonists classification

Anterior pituitary hormones
Thyroid and anti-thyroid drugs
Oral hypoglycemic drugs
Insulin and other injectables
Hyperglycemic agents 
Corticosteroids
Androgens and anti-androgens 
Anabolic steroids 
Drugs in erectile dysfunction
Estrogen and progestins 
Contraceptives 
Drugs acting on uterus 
Drugs affecting calcium balance

Cardio Vascular System Classification

Anti hypertensive drugs
Anti arrhythmic drugs 
Anti anginal drugs
Drugs for Chronic Heart Failure (CHF)
Drugs for Peripheral Vascular Disease (PVD)
Diuretics
Anti-diuretics
Coagulants 
Anti-coagulants
Anti-platelets
Hypolipidemic drugs
Fibrinolytics and anti-fibrinolytics
Hematinics
Plasma expanders
Sclerosing agents

Peripheral nervous system classification

Peripheral muscle relaxants
Central muscle relaxants  
Local anaesthetics

Central nervous system classification

Antidepressants 
Anti-anxiety drugs 
Antipsychotic drugs 
Antimanic drugs
Antiepileptic drugs
Anti Parkinsonian drugs 
Sedatives and hypnotics
General anaesthetics 
Opioids
CNS stimulants 
Cerebroactive drugs 
Psychotomimetics 
Antiaddictives

Autonomic nervous system classification

Cholinergic drugs 

Anticholinergic drugs 

Adrenergic drugs

Antiadrenergic drugs 

Ganglion stimulant and blockers