2. SPARE RECEPTOR
• Spare receptor also known as a “reserve receptor” or “efficacy
reserve” , refers to a phenomenon in pharmacology where a maximal
response can be achieved with only a fraction of the total available
receptors being occupied by a drug or ligand.
• Spare receptors are receptors that remain unbound when an agonist
is producing its maximal biologic response
3. SPARE RECEPTOR CONT…
• to determine the presence of spare receptors , scientists often
compare the concentration of drug needed to produce 50% of the
maximum effect(ec50) with the concentration of drug needed to
occupy 50% of receptors(kd).
• Spare receptors act as functional reserves and allows cells to
economically use endogenous agonists such as hormones and
neurotransmitters.
• The concept of spare receptors has important implications for drug
development and efficacy.
4. SPARE RECEPTOR CONT…
• It suggests that drugs targeting receptors with spare capacity can still
produce a full response even at lower concentrations or with partial
receptor occupancy.
• The existence of spare receptors also highlights the complexity of drug-
receptor interactions and the potential for multiple signaling pathways
to be activated or modulated.
• The spare receptors may play a role in maintaining receptor sensitivity
and responsiveness in certain physiological or pathological conditions.
• Overall, spare receptors provide a valuable concept in understanding
drug-receptor interactions and have implications for drug design, dosing,
and therapeutic efficacy.
