Gastrointestinal

Laxatives

Bulk forming

Increasing the mass:↑peristalsis. It's like eating more fibre (so get the pt to try this first).
E.g. Ispaghula husk (TN e.g. Fybogel)

Stimulant

↑Motility. Often cause cramp so avoid in intestinal obstruction. Excessive use can cause diarrhoea (and hence hypokalaemia).
E.g. Senna

Osmotic

Increase water in the large bowel.
E.g. lactulose (also useful in hepatic encephalopathy)

Proton Pump Inhibitors

Mechanism: Inhibit gastric acid secretion by blocking H-K pump.
Uses: Effective short term rx for gastric/duodenal ulcers. Also used for eradication of H pylori, prophylaxis of ulcers
Dose: Omeprazole 20mg 
Adverse Efects: GI disturbances (nausea, vomiting, abdo pain...), headache, dizziness

H2 Receptor Antagonists

Mechanism: Reducing acid output
Uses: 2nd line to PPIs usually
Adverse Effects: GI distrubance, altered liver function, headache, dizziness, rash, tiredness
Interactions: Is an CP450 inducer