L40 - Intro To Pharmacokinetics Flashcards
What is a dose?
Predetermined amount of the drug administered at one time to produce a certain degree of biological response
What is a dosage?
Predetermined amound and rate of administration of a drug for a patient
What a dosage form?
- Physical form in which precise mixture of API and excipients are presented
- help administration, deliver to sites of action, achieve rapid onset of action, improve bioavailability
What is a dosage regimen?
Schedule of doses of a therapeutic agent per unit of time (+ time between doses, time when dose given, amount of a medicine to be given at each specific time
What is a medicine or MP?
Substance/combination of, that is intended to treat, prevent or diagnose disease, or restore/correct.modify physiological functions by exerting a pharmacological/immunological/metabolic action
What is the API?
Substance in MP that is biologically active, produces desired effect
What is an excipient?
Constituent of medicine other than API
How did you establish a dosage regimen in the past?
Trial and error until satisfactory therapy achieved
- dose
- interval between doses
- route of administration
What is the design of a dosage regimen now?
Pharmacokinetics
- dosage regimen -> plasma conc = feedback
Pharmacodynamics
- site of action -> effects = feedback
What is pharmacokinetics?
Study of movements of foreign chemicals during their passage through the bosy, encompasses the kinetics of absorption, distribution, biotransformation/metabolism and excretion
What has PK contributed to?
- drug ADME
- dose - conc - effect relationship
- selection of best drug candidates
- rational dev of drug therapy
- establish dosage regimen
What is PK part of?
- preclinical studient and clinical studies in drug dev
- post marketing surveillance
- regulatory marketing submissions
What does the PK phase cover?
The relationship between drug input and drug conc achieved with time
What is PK simplified?
Science of the kinetics of drug absorption, distribution and elimination
What is biopharmaceutics?
study inter-relationship between
- physiochemical properties of drug, dosage form and route of admin
- the rate and extent of absorption, disposition of the drug
What does the PD phase cover?
The relationship between conc and both the desired and adverse effects produced with time
What is therapeutic window?
Range of conc between minimal conc (Cmin,eff) and max conc (Cmac.tox)
What is an assumption in pharmacotherapy?
Magnitude of therapeutic and toxic responses is a function of drug conc at site of action
What happens if the drug conc too low/too high?
- too low - no therapeutic effects, minimal conc (Cmin, eff)
- too high - toxicity, maximum concentration (Cmax, tox)
What is the objective of a dosage regimen?
Keep the drug conc inside the therapeutic window
Cmin,eff < Cdrug < Cmax,tox
Why are drug absorption and drug disposition processes complex?
- drugs move continuously
- events and ADME happen simultaneously
What is a model?
- set of mathematical expressions, describes quantitatively the processes involved in ADME and links
- hypothesis
What does the utility of a model hypothesis depend on?
- how well it has been built (selection of processes that govern ADME for each drug/dosage form and the description of them with mathematical functions)
- how well it describes the experimental/clinical observation
What are PK parameters?
Constants defined by the model which are characteristic for each drug
What are PK parameters egs?
- vol of distribution
- clearance
- elim rate constant, elim half life
- absorption rate constant (formulation dependent)
- freaction absorbed (formulation dependent)
What are variables of PK models?
- independent - time
- dependent - plasma, urine, tissue conc (experimental data)
What is the aim of a PK model?
Predict plasma, etc, conc of drug at a given time after admin of a drug
What is compartmental modellin in PK?
- body made one or more compartments
- compartment - body vol comprising of group tissues/fluids, similar properties such as blood flow and drug affinity, uniformly distributed in a compartment
- treatment of data uses first and zero order processes of entry into and exit from compartment
