Physiological effects of some common groups of drugs.

Beta-blockers

Voluntary and autonomic NS

Sympathetic and parasympathetic

Alpha and beta sympathetic receptors

Angina

Block the ability of the heart to respond to inotropic and chronotrophic stimulation therefore reduce myocardial oxygen demand therefore limit myocardial ischaemia.

Antihypertensives

Reduce cardiac output

Prevent constriction of peripheral vessels

May decrease renin secretion

Prophylaxis of migraine

What is their effect on?

* heart rate

* broncho tone

* peripheral circulation

* GI system

Diuretics

Loop diuretics

Very powerful

Used in renal or cardiac failure

Act on ascending loop of Henle to inhibit Cl transport

This acts on the counter current multiplier to reduce the hypertonicity of the medulla

Therefore less water is re-absorbed, therefore more left as urine

Thiazide type

Promote moderate diuresis

Act on the cortical segment of the distal tubule where they inhibit active transport of Na+

Alcohol is a diuretic.

Antibacterials

Most antibiotics work by preventing the reproduction of bacteria.

Resistance

Spectrum

Finish the course

Effects on the GI system

Penicillins and cephalosporins act by inhibiting the synthesis of the bacterial cell wall

Peptidoglycan is produced using peptidoglycan transpeptidase, which is inhibited

The cell membrane then osmotically bursts

Analgesics

Pain is a result of three areas of physiology,

Peripheral

Nociceptors detect pain in the periphery

Dorsal root horn

The path taken by pain fibres into the spinal cord, role of gate theory

Endorphine receptors also exist in the cord

Brain

There does appear to be nociceptor neurones in the brain in the reticular formation in the brain stem

Actual sensation of pain depends on several factors

Endorphine receptors and opium

Naloxone

Anti-coagulants

Heparin neutralises factor X, antidote is protamine sulphate

Oral anticoagulants interfere with the function of vit. K

Antiplatelet drugs like low dose aspirin reduce platelet stickiness

Thrombolytics

Fibrinolytics eg. streptokinase and urokinase. Fibrin is broken down to achieve thrombolysis

Bronchodilators

Some stimulate the sympathetic bronchial receptors to

cause bronchodilation eg. salbutamol

Others inhibit the parasympathetic receptors eg. ipratropium