Questions and Answers
What is the primary site of drug absorption in the body?
What is the function of pharmacokinetics?
What does the first pass effect refer to?
How do hydrophilic drugs typically leave the bloodstream?
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Which intermolecular force is primarily involved with hydrophobic tails of phospholipids?
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What characteristic of the small intestine makes it ideal for drug absorption?
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What happens to oral drugs before they circulate in the body?
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Which of the following correctly describes the role of the polar heads of phospholipids in the cell membrane?
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What is the effect of ionization on a drug's water solubility?
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At what pH will an arylamine be 50% ionized?
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Which statement accurately describes the ionization behavior of phenol?
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What is the conjugate base of phenol?
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Which amino acids are negatively charged and have high pKa values?
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Which of the following statements is true about bases in acidic solutions?
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What occurs to arylamine when placed in an acidic environment?
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Which of these compounds is classified as a base?
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What is the normal molecular weight range for effective synthetic drugs?
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Which factor is NOT mentioned as controlling the 3D structure of a drug molecule?
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Which hybridization state is described as fully saturated and tetrahedral?
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What is the significance of induced fit in pharmacology?
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What does the decorated scaffold model help with?
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Which statement about unionized drugs is correct?
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Which of the following is a correct description of Sp2 hybridization?
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What is an essential property for the absorption of drugs?
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What does a (+) π value indicate about a substituent's contribution to hydrophobicity?
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What is the ideal range for the partition coefficient, P?
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Which formula represents how to calculate π?
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What does a water-soluble compound typically have with respect to its log P value?
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Why do drugs need to be hydrophilic?
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Which of the following is an example of a substituent that would yield a (-) π value?
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What is the primary purpose of using log D in drug chemistry?
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What does it indicate if a substituent is limiting the hydrophobicity of a drug?
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Which amino acids are charged and acidic with low pKa’s?
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Which amino acids would be fully ionized at a stomach pH of 2?
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What is true when pKa and pH are equal?
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What is bulk flow transfer?
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How does diffusional transfer differ from bulk flow transfer?
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What does a log P value indicate about a molecule?
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What is a partition coefficient (P)?
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What happens when you increase the concentration of a drug in octanol?
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Study Notes
Physiological Properties of Drug Molecules
- Drugs encounter approximately 10,000 targets in the body.
- Pharmacodynamics: Refers to what the drug does to the body.
- Pharmacokinetics (ADME): Refers to what the body does to the drug, consisting of absorption, distribution, metabolism, and excretion. Effective drugs require relevant concentrations at their site of action.
Absorption
- The primary site of absorption is the small intestine, due to its large surface area.
- Minor absorption also occurs in the mouth and large intestine; however, the stomach mainly breaks down drugs because of its acidic pH (around 2).
First Pass Effect
- Oral drugs must pass through the liver before distribution throughout the body, resulting in some loss due to hepatic metabolism.
Drug Transport Mechanisms
- Hydrophilic drugs leave the bloodstream via capillary pores or transport proteins; larger proteins cannot pass easily.
- No capillary pores exist in the blood-brain barrier.
Cell Membrane Interaction
- Van der Waals forces mediate the interaction between hydrophobic tails of phospholipids.
- Polar heads interact with the aqueous outside environment, forming a hydrophobic barrier around the cell.
- Induced fit is crucial for the pharmacological effects of drugs.
Physiochemical Properties
- Key properties include stereochemistry, acid/base characteristics (e.g., pKa and ionization), and water solubility influenced by hydrogen bonds.
Molecular Weight of Drugs
- An effective molecular weight for synthetic drugs typically falls between 200-500 Da, involving elements such as C, H, N.O.P, S, Br, Cl, I, and occasionally B.
Decorated Scaffold Model
- A method for diagramming drug molecules to represent functional groups in proper 3D configurations for binding.
3D Structure Control
- Controlled by the static arrangement of groups around a stereogenic center and the dynamic conformation of the molecule.
Hybridization of Carbon
- Carbon can have three hybridization states:
- sp3: Tetrahedral, fully saturated (e.g., oxygen and nitrogen configurations).
- sp2: Trigonal planar and unsaturated.
Ionization
- Ionized drugs are more water-soluble but poorly absorbed through cell membranes; non-ionized drugs are lipid-soluble and easily absorbed.
- Acids and bases behave differently regarding ionization depending on the pH of the environment (acid does not ionize in acidic conditions, while a base does).
Properties of Phenol and Arylamine
- Phenol: A weak acid (pKa 9-11), mostly unionized in the stomach due to low pH.
- Arylamine: A basic compound (pKa 9-11) that readily ionizes in acidic conditions, forming a positively charged arylammonium at low pH.
Amino Acid Charge Characteristics
- -charged acidic amino acids: Cysteine and tyrosine.
- -charged acidic amino acids with low pKa: Aspartic acid, glutamic acid.
- Basic amino acids: Arginine (pKa 12.5), lysine (pKa 10.5), histidine (pKa 6).
pKa and pH Relationship
- pKa represents the pH at which the concentrations of ionized and unionized forms are equal.
- At a stomach pH of 2, basic amino acids will be fully ionized.
Drug Movement in the Body
- Bulk Flow Transfer: This is how drugs circulate throughout the body, independent of structure, post-absorption.
- Diffusional Transfer: Movement of molecules across non-aqueous barriers like cell membranes, dependent on drug structure and possibly requiring transporters.
Log P and Partition Coefficient
- Log P: Indicates a molecule's hydrophilicity and lipophilicity; values ≤ 0.5 suggest water solubility, while values > 0.5 indicate water insolubility.
- The partition coefficient (P) describes hydrophobicity, calculated as the ratio of drug concentration in organic material to that in water.
π Coefficient
- π measures the contribution of a functional group to the partition coefficient P, which helps identify interactions with hydrophobic binding sites.
- A positive π value indicates increased hydrophobicity compared to hydrogen, while a negative π value suggests reduced hydrophobicity.
Drug Properties
- A typical water-soluble compound has a log P value of less than 0.5.
- Drugs must be hydrophilic for body distribution and hydrophobic to diffuse across cell membranes.
- Log D: Used to describe compounds with ionizable groups and their behavior in different pH environments.
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Description
Test your understanding of the physiological properties of drug molecules with this quiz. Covering key concepts in pharmacodynamics and pharmacokinetics, you'll explore how drugs interact with the body and their various targets. Perfect for those looking to deepen their knowledge in pharmacology.
