2. How do drugs work

Question 1

How do drugs work?

x7 mechanisms with examples

Answer 1

Drugs produce their effects by acting on numerous different systems within
the body.

Below is a list of the effecter sites at which drugs act, along with some clinical examples.

1. Receptors
   a Ligand-gated ion channels
   • Suxamethonium is an agonist at nAChR while rocuronium is an antagonist.

• Diazepam is an agonist at GABAA receptors while flumazenil is an antagonist.

b G-protein-coupled receptors

• Dobutamine is an agonist at β-adrenoceptors while atenolol is an antagonist.

• Morphine is an agonist at opioid receptors
while naloxone is an antagonist.

c Tyrosine kinase receptors
• Insulin is an agonist at insulin receptors.
d Intracellular receptors
• Hydrocortisone is an agonist at steroid receptors.

2. Ion channels
   • Lignocaine blocks the fast Na+ channels.
   • Verapamil blocks L-type Ca2+ channels.
3. Enzymes
   • Neostigmine inhibits acetylcholinesterase.
   • Aspirin inhibits cyclo-oxygenase 1 and 2.
4. Hormones
   • Carbimazole reduces thyroxine production.
   • Metformin increases insulin production.
5. Neurotransmitters
   • Ephedrine increases presynaptic noradrenaline release.
   • Amitriptyline and cocaine reduce noradrenaline reuptake.
6. Transport systems
   • Digoxin inhibits the cardiac Na+/K+ ATPase pump.
   • Furosemide inhibits the Na+/K+/2Cl
   – ATPase pump in the loop of Henle.
7. Physicochemical
   • Sugammadex chelates rocuronium.
   • Antacids neutralise gastric acids.