Basic Principles of Receptor Pharmacology, Pharmacokinetics and Pharmacodynamics Flashcards
(27 cards)
Define the basic principles of pharmacology
The study of drugs and their interactions with the human body. It embraces the knowledge of the source, physical and chemical properties, compounding, physiological actions, absorption, fate, excretion, and therapeutic uses of drugs.
Define a drug interaction
The effect of one drug (object drug) is changed by another drug (precipitant drug), either desired or undesired
Differentiate between an agonist and antagonist
Agonist: interaction between two or more drugs resulting in a pharmacologic response greater than the sum of individual responses to each drug (1+1=5)
Antagonist: Opposition in action or smaller combined effect than individual agents (2+2=1)
Discuss the theory of up and down regulation
Overtime, the body becomes tolerant to the same dose of the same drug.
-Downregulation: long-term reductions in receptor number which occur in response to continuous exposure to agonists
-Upregulation: increases in receptor number which occur when receptor activation is blocked for prolonged periods by pharmacologic antagonists
Describe the major types of drug/receptor signaling
- Transmembrane diffusion of the drug to bind to an intracellular receptor
- Transmembrane enzyme receptors, whose outer domain provides the receptor function and inner domain provides the effector mechanism converting A to B
- Transmembrane receptors that, after activation by an appropriate ligand, activate separate cytoplasmic tyrosine kinase molecules (JAKs), which phosphorylate STAT molecules that regulate transcription (Y, tyrosine; P, phosphate)
- Transmembrane channels that are gated open or closed by the binding of a drug to the receptor site
- G protein-coupled receptors, which use a coupling protein to activate a separate effector molecule
Define the basics of Pharmacokinetics
The absorption, distribution, metabolism and elimination of drugs.
Define the basics of Pharmacodynamics
The action of a drug on the body and the study of the biochemical and physiological effects of drugs and their mechanism of action
Describe the processes of pharmacokinetics
Absorption: Broken down in stomach and absorbed into the bloodstream
Distribution: Where is the drug going/Can it cross barriers?
Metabolism: Liver metabolizes the chemical
Elimination: Usually through the kidneys (urine), can also be through intestines, skin, breast milk or lungs
List factors that may affect the rate and extent of drug absorption
Regional blood flow, type of tissue, drug’s chemical properties, limitation of physiologic transport processes
What is drug bioavailability?
The proportion of a drug dose that reaches systemic circulation
Define lipophilic drug molecules
Fat soluble molecules that cross cell membranes easily
Define hydrophilic drug molecules
Water soluble molecules that cross cell membranes slowly
What is the first pass effect?
Oral drugs that are absorbed by the GIT are circulated to the liver first via the hepatic portal vein. The liver acts as a filter, and only part of the drug is circulated systemically.
What drugs bypass the first pass effect?
IV drugs, rectal suppository drugs
Reyataz requires an acidic pH for gastric absorption. Zantac is a gastric acid suppressant that raises gastric pH. How will Zantac affect the absorption of Reyataz?
It will decrease the absorption of Reyataz
Determine vancomycin’s Vd: A 70kg male patient receives 1500mg of vancomycin IV. One hour later, the blood concentration is 50mg/L. What is vancomycin’s Vd (in liters) in this patient?
30L
Your patient is seizing! Calculate a phenytoin loading dose!
Cp desired = 15mg/L
Vd = 0.7L/kg
Patient weight = 70kg
735mg
Tigecycline has a very large Vd, Daptomycin has a small Vd. Which antibiotic is better for treating endocarditis?
Tigecycline
Where does metabolism primarily occur?
The liver
What is a substrate?
The drug that is metabolized by a CYP450 enzyme
What is an inducer?
The molecule that increases CYP450 enzyme activity. It enhances the metabolism and clearance of a substrate
What is an inhibitor?
The molecule that decreases CYP450 enzyme activity. It slows metabolism of the substrate and leads to greater drug concentration
JT is a 60 year old man with recently diagnosed atrial fibrillation. He is prescribed warfarin, an anticoagulant, to reduce his risk of embolic stroke. He is also prescribed amiodarone to prevent further episodes of afib. Warfarin is a substrate of CYP450 2C9 and amiodarone is an inhibitor of CYP450 2C9. Anticipate the drug interaction.
It will increase the effects of warfarin and the patient could potentially bleed out with trauma.
What is the consequence of this drug-drug interaction?
Efavirenz + Ortho Tri-Cyclen
- Efavirenz is a strong inducer of CYP3A4
-Ortho Tri-Cyclen is metabolized by CYP3A4
Ortho Tri-Cyclen will become less effective
