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Questions and Answers
What does ADME stand for in pharmacokinetics?
What does ADME stand for in pharmacokinetics?
Absorption, Distribution, Metabolism, Elimination
What is the primary focus of pharmacodynamics?
What is the primary focus of pharmacodynamics?
What the drug does to the body
Which physicochemical properties affect the pharmacokinetic profile of a drug? (Select all that apply)
Which physicochemical properties affect the pharmacokinetic profile of a drug? (Select all that apply)
The route that involves IV, IA, and intraspinal administration is known as the ______ route.
The route that involves IV, IA, and intraspinal administration is known as the ______ route.
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Weakly acidic drugs dissolve better in a basic environment in the gastrointestinal tract.
Weakly acidic drugs dissolve better in a basic environment in the gastrointestinal tract.
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What is the Henderson-Hasselbalch equation used for?
What is the Henderson-Hasselbalch equation used for?
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What does the partition coefficient (log P) indicate in pharmacology?
What does the partition coefficient (log P) indicate in pharmacology?
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Which factors influence passive diffusion of drugs? (Select all that apply)
Which factors influence passive diffusion of drugs? (Select all that apply)
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What are common sites of loss for drugs in the body?
What are common sites of loss for drugs in the body?
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What primarily governs the absorption rate of a drug during passive diffusion?
What primarily governs the absorption rate of a drug during passive diffusion?
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Study Notes
Pharmacokinetic (ADME) Properties
- The body's action on the drug, including absorption, distribution, metabolism, and elimination.
- Medicinal chemists must understand these properties to design effective drugs.
Pharmacodynamic Properties
- The drug's action on the body, including physiological response, mechanism of action, and dose-response curve.
Physicochemical Properties and Drug Action
- Slight modifications in a drug's structure can cause dramatic activity changes, often related to specific physical factors.
Key Physical Properties Affecting Pharmacokinetic Profile
- Partition coefficient (log P): Relates to the drug's solubility in lipids versus water.
- Dissociation constant (pKa): Determines the ionization state of a drug at different pHs, impacting absorption and distribution.
- Steric factor: Relates to the size and shape of the molecule, impacting binding, absorption, and metabolism.
- Solubility: The ability of a drug to dissolve in a solvent, directly impacting absorption.
- Polymorphism: Different crystal forms of a drug, potentially affecting solubility and dissolution rate.
Routes of Administration
- Parenteral: Injections, including IV, IA, intraspinal, IM, SC, and IP. This bypasses the gastrointestinal tract, offering faster absorption.
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Gastrointestinal Tract (GIT): Oral administration, requiring drug dissolution in GIT fluids. The dissolution rate depends on:
- Particle size: Smaller particles have greater surface area, promoting faster dissolution.
- pH of the medium: Weakly acidic drugs dissolve better in basic regions of the GIT and vice versa.
Absorption Mechanisms
- Active transport: Energy-requiring transport against the concentration gradient. Requires similarity between the drug and the natural substrate.
- Passive diffusion: Drug movement down the concentration gradient, no energy required.
- Convective absorption: Passive transport of small molecules through water-filled pores in the membrane.
Passive Diffusion Factors
- Rate of diffusion is proportional to the drug concentration at the absorption site.
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Important factors influencing passive diffusion:
- Area of the membrane: Larger area, faster diffusion.
- Thickness of the membrane: Thinner membrane, faster diffusion.
- Partition coefficient of the drug: Higher lipid solubility, faster diffusion through cell membranes.
Dissociation Constant (pKa)
- Most drugs are either weak acids or weak bases.
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Henderson-Hasselbalch Equation:
- For weak acids: pH = pKa + log ([salt]/[acid])
- For weak bases: pH = pKw - pKb + log ([base]/[salt])
Partition Coefficient (log P)
- The ratio of a drug's concentration in an organic phase to its concentration in an aqueous phase at equilibrium.
- Higher log P values indicate greater lipid solubility.
Sites of Drug Loss
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Protein binding: Drugs can bind to proteins in the bloodstream.
- Advantages: Act as a temporary storage site, releasing free drug slowly, potentially contributing to longer duration of action.
- Metabolism: The process of breaking down drugs in the body.
- Excretion: Eliminating the drug from the body.
- Storage sites: Drugs accumulate in specific tissues, such as neutral fat.
Protein Binding
- Drugs can form complexes with proteins in the bloodstream.
- The complex is generally inactive, while the free drug is the active form.
- Protein binding can affect the distribution and elimination of a drug.
Neutral Fat
- Drugs can partition into neutral fat based on factors like:
- Partition coefficient: Log P
- Ionization constant: pKa
Excretion
- For a drug to be excreted in urine:
- Polarity: Drugs need to be polar to be eliminated in urine.
- pH manipulation: Adjusting urine pH can enhance excretion.
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Description
Explore the crucial concepts of pharmacokinetics and pharmacodynamics in drug design. This quiz covers key properties such as absorption, distribution, metabolism, and elimination, as well as the physicochemical factors that influence drug action. Test your knowledge on how these properties affect drug efficacy and safety.
