Questions and Answers
Define pharmacokinetics.
Pharmacokinetics describes the movement of a drug in the body, focusing on how the body acts on the drug.
What are the main components of ADME in pharmacokinetics?
Match the following drug administration routes with their examples:
Oral = Convenient self-administered route Injectable = Parenteral route Transdermal = Administration through the skin Inhalation = Administration through breathing
Lipid diffusion is a primary mode of movement for drugs in the body.
Signup and view all the answers
What is bioavailability in pharmacokinetics?
Signup and view all the answers
Explain the concept of prodrug.
Signup and view all the answers
What are the advantages of bypassing limitations of oral administration?
Signup and view all the answers
Which route of administration provides immediate onset of drug action?
Signup and view all the answers
Drugs administered through mucous membranes avoid the first pass effect. (True/False)
Signup and view all the answers
In biotransformation, Phase II reactions involve the conjugation of drugs to create highly polar ________________.
Signup and view all the answers
Match the drug metabolism factors with their corresponding influences: Genetics, Age and Sex hormones, Diet and Environment, Disease
Signup and view all the answers
What is the primary mechanism that limits reabsorption of drugs in the renal tubules?
Signup and view all the answers
What is enterohepatic recycling in drug excretion?
Signup and view all the answers
Breast milk being more acidic than plasma may lead to concentration of basic compounds in it.
Signup and view all the answers
What is the main route for the excretion of volatile materials like nitrous oxide?
Signup and view all the answers
What does the term 'elimination' refer to in pharmacokinetics?
Signup and view all the answers
For a drug administered at steady state, what does [Csteady state] represent in terms of dosing calculation?
Signup and view all the answers
Study Notes
Pharmacokinetics
- Definition: Describes the movement of a drug in the body (how the body acts on the drug)
- ADME: Absorption, Distribution, Metabolism, and Excretion
- Importance: The body's actions on the drug affect the drug's efficacy and toxicity
Absorption
- Definition: Process of a substance entering the blood circulation
- Factors affecting absorption:
- Physical state of the drug
- Water/lipid solubility
- Particle size
- Ionization of the drug
- Disintegration time of the drug
- Modes of movement:
- Aqueous diffusion
- Special carriers
- Endocytosis and exocytosis
- Lipid diffusion (most important)
- Weak acids and weak bases: only non-ionized forms can diffuse through the lipid membrane
Distribution
- Definition: Dispersion or dissemination of substances throughout the fluids and tissues of the body (to the site of action)
- Factors affecting distribution:
- Blood flow
- Plasma protein binding
- Lipid solubility
- pH
- Volume of distribution (Vd): The apparent volume of fluid that the drug is distributed in
- Importance of distribution: To produce a characteristic effect, a drug must present at an appropriate concentration at its intended site of action
Routes of Administration
- Enteral (oral, sublingual, rectal)
- Parenteral (injectable, transdermal, inhalation)
- Advantages and disadvantages of each route
First Pass Metabolism
- Definition: Drug passes through the liver where it is metabolized (inactivated) and/or excreted into the bile
- Importance: Affects bioavailability and efficacy of the drug
Prodrug
- Definition: A drug that is inactive in its administered form and must be converted to an active form in the body
- Importance: Takes advantage of first-pass effect to activate the drug
Metabolism
- Definition: Biotransformation, may change the substance to a more active form or inactive form
- Phase I: Addition of a polar functional group to prepare for conjugation
- Phase II: Conjugation or hydrolysis reactions to make the drug more readily excreted
- Cytochrome P450 (CYP) enzymes: important for Phase I metabolism
- Induction and inhibition: effects of other substances on CYP enzymes
Excretion
- Definition: Removal from the body
- Renal excretion: major route of excretion
- Biliary excretion: minor route of excretion
- Other routes: respiration, breast milk, sweat, saliva, and tears
Elimination Kinetics
-
Definition: The sum of the pharmacokinetics that contribute to the removal of an administered drug
-
Importance: Determines the duration of the drug's effect### Clinical Pharmacokinetics
-
Formula to calculate half-life (t½): t½ = (0.693 x Vd)/Clearance
-
Formula to calculate steady-state concentration [Csteady state]: [Csteady state] = (Bioavailability x Dose)/(Dosing interval x Clearance)
-
Formula to calculate doseloading: Doseloading = Vd x [Csteady state]
-
Formula to calculate dose maintenance: Dosemaintenance = Clearance x [Csteady state]
-
Formula to calculate clearance: Clearance = (0.693 x Vd)/t½
-
Formula to calculate volume of distribution (Vd): Vd = (t½ x Clearance)/0.693
-
Alternative formula to calculate Vd: Vd = Dose/[Plasma]
Case Scenario 1: Adverse Drug Reaction
- A 58-year-old patient presents with dizziness, nausea, vomiting, and palpitations
- The patient is prescribed medication for hypertension
- Labs reveal elevated BUN and serum creatinine, indicating Acute Kidney Injury (AKI)
- The most likely explanation is a drug-drug interaction affecting kidney function
Case Scenario 2: Drug Interaction with Oral Contraceptives
- A 27-year-old female presents with abdominal pain, nausea, and vomiting
- The patient is prescribed oral contraceptives and has been taking St. John's Wort supplements
- Urine dipstick for human chorionic gonadotropin (HCG) is positive, indicating unintended pregnancy
- The best explanation is that St. John's Wort induces CYP3A, which accelerates the metabolism of oral contraceptives, reducing their effectiveness
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about pharmacokinetics, the movement of a drug in the body, and absorption, the process of a substance entering the blood circulation. Understand the factors affecting absorption and its importance in drug efficacy and toxicity.