General Principles of Clinical Pharmacology, Pharmacokinetics and Rational therapy Flashcards
What is clinical pharmacology?
- the relationship between drugs and their clinical use in all aspects
- the aim is the achieve optimal pharmacotherapy
- To study: pharmacokinetics, pharmacodynamics, drug interaction, adverse effects, efficacy & safety etc
What is pharmacotherapy?
- application of drugs in the prevention treatment or diagnosis of disease
- drug use in purposeful alteration of normal function
What is rational prescribing?
- Make a Dx
- Understand the pathophysiological implications of the Dx
- Objective for therapy
- Drug choice
- Plan for monitoring drug effectiveness, its action and determine the endpoint for therapy
- Plan a program to educate the patient
What is irrational prescribing?
- AB resistance development
- Prolonged hospitalisation
- Delay in cure
- Loss of patient trust in physician
- Lowering health standards etc
What are the 7 steps to selecting a “Personal drug”?
1) Make Dx
2) Therapeutic objective?
3) Gather effective groups of drugs
4) Choose an effective group according to criteria: efficacy, safety, cost etc
5) Choose a personal drug
6) Provide eduction and info on this drug to patient
7) Monitor patient and stop treatment when suitable
What must be considered when administering drugs?
- Age
- Renal status
- Liver function
- Polymorphisms
- Cytochrome P450 (genetics, drug interaction etc)
What are clinical pharmacokinetics and pharmacodynamics?
-The relationship between dose and effect can be separated into pharmacokinetics (dose-concentration) and pharmacodynamics (concentration-effect) components
- Concentration provides the link between the two
- Allows the “Target Concentration” for rational dosing
Pharmacokinetics- absorption, distribution and elimination
Pharmacodynamics- effect of the drug at the site of action, dose-response curve and influence of other factors on the effect of the drug
What is target concentration strategy?
1) Estimate the initial dose
2) Begin therapy
3) Assess therapy- patient response and drug level
4) Refine estimate dose
5) Adjust dose- refer then back to assess therapy
What is pharmacogenomics?
- the study of genetic variations that cause differences in drug response among individuals or populations
- some patients respond with greater than usual sensitivity to standard doses
- possibly due to small genetic modifications
- reduced activity of particular enzyme responsible for eliminating the drug
What factors should be considered when deciding initial doses for drugs?
- Check renal function if the drug will be primarily eliminated by the Kidneys
*Check creatinine concentration and convert the value into creatinine clearance - Check liver function if the drug will be primarily eliminated hepatically (Child-Pugh Score)
What is therapeutic drug monitoring (TDM)?
- TDM is the management of a patient’s drug regimen based on the serum, plasm or whole blood concentration of a drug
- enables assessment of efficacy and safety of certain meds
- Goal: individualism therapeutic regimen for optimal benefit
*only useful for drugs with poor correlation between dose and clinical effect
What are some examples of TDM indications?
- unpredictable relationship with dose and plasma concentration e.g. phenytoin
- drugs with narrow therapeutic window
- drugs with steep dose-response curve
- drugs difficult to predict end point or clinical response
What pharmacokinetic parameters are essential for TDM?
- Bioavailability
- Volume of distribution and distribution phases
- Clearance
- Half-life
- Protein binding of drugs
Clinical significance of TDM?
- Maximises efficacy
- Avoids toxicity
- Identifies therapeutic failure e.g. non compliance
- Facilitates therapeutic effect of drug by achieving target drug concentration
