Pharmacodynamics Flashcards
Describe water as a drug target
Drugs can target the balance of water and fluids within the body. As a result, they can change the water concentration, hydrating or dehydrating certain organs/sites within the body.
Describe H+ ions as a drug target
H+ ions are targeted when the pH levels in the body needs to be changed. For example, ammonium chloride is used to acidify urine and thus lower pH levels within the body. The liver metabolises the ammonium into urine, and the Cl- is excreted into urine. The loss of Cl- obligates the loss of H+
Describe metal ions as a drug target
Are targets in cases of poisoning. Chelating agents basically bind metal ions together and make them inert = less poisonous, changing their solubility and enabling it’s excretion. An example is EDTA which works on ions like Pb ++
Describe enzymes as drug targets
Some drugs can either inhibit or activate enzymes. For example, you might want to inhibit enzymes that are favourable to pathogens. The issue is ensuring the drug is extremely specific to enzymes so that enzymes essential for metabolic pathways are unaffected.
Describe nucleic acids as drug targets
DNA and RNA may become targets for antimetabolites and some antibiotics. DNA/RNA is present within cancer cells and viruses, so drugs can help block replication and protein functions of nucleic acids.
Cisplatin is a commonly used as an anticancer drug. It crosslinks DNA strands, hence inhibiting DNA replication.
Describe non-specific binding to a receptor as a drug target
These drugs do not bind to receptors. Instead, they alter the shape or cause the dislocation of receptors, affecting their ability to work.
Anaesthetics for instance, work by disrupting the phospholipid bilayer. Integral proteins binding ability to ligands are consequently affected.
Describe specific binding to a receptor as a drug target
Drugs specifically bind to receptors; intracellular receptors, ion-gated channels, G-protein receptors and enzyme linked receptors.
Describe the types of agonists with examples (3)
Endogenous agonists: naturally produced molecules that can bind and modulate a receptor. FOR EXAMPLE seratonin for the seratonin receptors
Full agonist: Can bind and activate the receptor at 100% efficacy. FOR EXAMPLE isopterenol mimics the exact effect of adrenaline to its receptors
Partial agonists: Has a lower efficacy than a full antagonist. It cannot produce a maximal response even if all receptor sites are occupied. FOR EXAMPLE buprenorphine binds opiate receptors as a partial agonists thus relieving the dependence symptoms on opioid drugs
Describe antagonists with examples
Competitive antagonists binds to the same site as the agonist to block the agonist’s action. Therefore their inhibitory effects can be overcome by additional doses of the agonist. To achieve the same EC50, you need higher doses of the agonist
Non-competitive antagonistbinds to an allosteric (non-agonist) site on the receptor to prevent activation of the receptor. The main affect of a noncompetitive antagonist is to reduce the maximum effect of the agonist; EC50 decreases.
What does EC50 and LC50 refer to?
EC50 (Half maximum effective concentration): Refers to the concentration of the drug needed to achieve 50% of final effect
LC50 (half lethal concentration): Refers to the concentration of the drug needed to achieve 50% of mortality from toxicity
What is selectivity in terms of drugs? Provide an example.
• Most drugs are Selective: This means if the concentration increases, they can act on multiple processes (eg can bind more than one type of receptor)
Example: Verapamil blocks some Ca2+ channels but can also block Na channels in high concentrations
Which drugs helps with poisoning?
EDTA works on Pb++
Which drug acts on nucleic acids?
Cisplatin = cross linking of DNA which inhibits replication ability
Provide an example of a selective drug.
Verapamil blocks some Ca2+ channels but can also block Na channels in high concentrations
List the types of drug targets (7)
- H+ ions
- Water
- Nucleic acids
- Enzymes
- Metal ions
- Binding to a specific receptor
- Non-specific binding to a receptor
