Agonist responses - = a ffi nity and e ffi cacy - Full agonist = - - PowerPoint PPT Presentation

One 2 One Medicine: Pre-clinical revision course

• = affinity and efficacy
• Full agonist = can generate

maximum response

• Spare receptors
• Partial agonist = cannot

generate max

• EC50 = concentration for 50%

drug's maximum response

Agonist responses

One 2 One Medicine: Pre-clinical revision course

• = affinity and efficacy
• Full agonist = can generate

maximum response

• Spare receptors
• Partial agonist = cannot

generate max

• EC50 = concentration for 50%

drug's maximum response

Agonist responses

One 2 One Medicine: Pre-clinical revision course

Response Log [agonist]

High efficacy full agonist 100% Spare receptors Lower efficacy full agonist Partial agonist 50% 100% 50% EC50

One 2 One Medicine: Pre-clinical revision course

• Binds with affinity and no efficacy
• Competitive = same binding site as agonist
• Dissociates away
• Can be overcome
• Non-competitive = irreversible (covalent)
• Removes receptor once bound
• Increasing agonist has no effect
• Allosteric agonist / inhibitor = binds at different site

Antagonist responses

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One 2 One Medicine: Pre-clinical revision course

Response Log [agonist]

100% Competitive antagonist Non-competitive antagonist

Antagonist responses

One 2 One Medicine: Pre-clinical revision course

• G-proteins are activated by GTP, causing subunit

dissociation

• Increased ionisation of drugs reduces transmembrane

passage

• Zero order elimination has a fixed amount removed per

hour, with variable half-life

• Competitive antagonists can be overcome by

increasing agonist concentration

Key points