Lecture slides week 1 Flashcards
What is rational prescribing?
Prescribing decisions that are
-evidence based
-interpreted in the context of factors not accounted for in any clinical trial (system, patient, drug, prescriber)
-maximize effectiveness
-minimize harms
-avoid waste of resources
-respect patient choice
Describe patient factors that affect prescribing
Diagnosis, medical history (allergies, genetics, risk factors, comorbidities), drug history (i.e., history of adverse effects), exam findings, investigations (labs, XR, urine, etc.), ability to obtain/ pay for Rx, ability to follow instructions, prognosis
Describe drug factors influencing prescribing
Side effects, interactions with patient (their comorbidities, other drugs they are on), kinetics and dynamics
Describe prescriber factors influencing prescribing
Provider familiarity/ comfort, ability to make referrals/ follow up
Describe system factors influencing prescribing
Drug availability, insurance coverage, restrictions
Describe the rational prescribing process
Diagnosis
Prognosis
Goals of therapy
Treatment selection
Monitoring and follow up
What is the most important component of making the diagnosis?
History per Susan (helps form ddx, obtain allergies/ hx )
If you don’t have time to do a hx/ physical/ ddx, you probably aren’t prescribing rationally!
What components are important in making a diagnosis?
History, physical, differentials, diagnostics (if necessary), working diagnosis
How does prognosis affect prescribing decisions?
Prognosis helps shape goals of care
I.e., QOL goals vs. curative intent
What is the patient willing to do? Will they be able to use the therapy? Do comorbidities (i.e., liver, kidney) affect the drug choice? (i.e., patient with declining liver fcn).
Name a few different goals of therapy
Cure, relief of symptoms, long term prevention of negative effects of disease, replacing deficiencies, therapeutic trials to aid in diagnosis
When there is more than one treatment option available, how do you decide which one to pick?
-Maximize benefit harm balance, consider patient factors, drug factors, prescriber factors
i.e., drug availability, cost, community support, side effect profile, dosing profile, your competence/ experience with a drug
T/F Drugs in the same class may have different bioavailability, dose concentration curves, and half lives that will determine their dosing schedule
True
What are some pharmacokinetic factors to consider when prescribing?
Absorption- what route is feasible/ will the patient tolerate?
Distribution- i.e., giving an anemic person a highly protein bound drug won’t work
Metabolism: any drug interactions to be aware of? How is their liver function?
Excretion: Kidney function/ adjusting for renal dosing
What are some pharmacodynamic factors to consider when prescribing?
Therapeutic index
Dose response curve
Need for monitoring
T/F when choosing between drug A and B, you want to pick the drug with a more narrow therapeutic index in order to have precise effects
False- want wider for less chance of side effect or toxicity
T/F Rational prescribing means making prescribing decisions based on the specific disease process
False- make decisions based on the patient, not the diseasee
What are some consequences of irrational prescribing?
Low benefit, increased risk of harm, reduced adherence, unnecessary cost
What is multimorbidity?
Multiple (2+) long term conditions (can be physical/ mental, learning disabilities, sensory or spectrum disorder, alcohol and substance misuse)
What is deprescribing?
Planned and supervised process of dose reduction or stopping medication that might be causing harm, is is no longer of benefit.
Part of good prescribing.
How might one incorporate principles of deprescribing into practice/
-review prescribed, OTC, supplemental therapies at every encounter
-reduce or discontinue preventive medications when benefit is no longer a consideration (i.e., when 2-10 year outcomes will not be achieved)
-reduce or discontinue medications that are not needed or could be replaced by something less harmful
Define pharmacotherapeutics
The study of the therapeutic uses and effects of drug
For clinicians to be safe and effective in their approach to therapeutics, they should have a strong understanding of the ______________ and __________________ of drug therapy.
Pick from: safety profile, cost effectiveness, kinetics, dynamics, tailoring, negatives, benefits, harms
Kinetics and dynamics. You need to know the kinetics and dynamics to be safe!!!
What is pharmacokinetics?
Study of absorption, distribution, metabolism, and elimination of drugs
(Body effect on drugs)
Why do we care about pharmacokinetics?
Determines how rapidly and for how long the drug will appear at the target organ
Define absorption:
The method in which a drug is introduced to the body
What is the general relationship between route of absorption and onset of pharmacologic effect?
In general, the pharmacological effect that is desired will be delayed the further it is away from the systemic circulation
Describe some drug factors influencing absorption
Route of administration, dosage form, molecular weight, lipid solubility, degree of ionization, drug solubility, chemical stability in gastric pH
What patient factors influence absorption?
Body size, maturation of organ function, pathologic processes
What is bioavailability?
In a typical use of the drug, how much is available AT THE SITE OF ACTION unchanged
Do I need to calculate bioavailability for every patient?
No, drugs come with bioavailability information. It is the “best case scenario” how much drug will be at the side of action unchanged. The drug is designed this way.
How does oral vs. IV administration of a drug influence its effect?
Oral- GI system > liver > circulation (takes more time, subject to first pass metabolism by liver)
IV > enters directly into circulation, bypassing the GI system and liver
Which route has the most immediate peak concentration in the blood? Inhalation, oral, or intravenous
Inhalation > intravenous > oral
Inhaled drugs reach arterial circulation faster than drugs injected into the vein
Define bioavailability
Concentration of drug available at site of action unchanged.
Here is another definition from the slide set:
The fraction of drug that is available unchanged that is absorbed into the systemic circulation after extravascular administration and passing the biologic barriers is defined as its bioavailability
What influences bioavailability?
Dose of drug, availability of membrane transported, amount of drug that enters systemic circulation, volume of distribution, how quickly metabolism and excretion take place
Why is drug binding significant in kinetics?
Drugs may bind to transport proteins in the blood to travel around circulation. However, it is important to note that only unbound drug (1) provides the driving force for distribution of the agent to the body tissues (2) has effects on its intended target
T/F Binding (by a tissue or protein) is reversible
Usually yes- this allows unbound and bound forms of the drug to find an equilibrium in the body.
What may cause a drug to be incompletely absorbed?
-Poor absorption in gut
-Too hydrophilic- cant cross lipid cell membrane
-Too lipophilic- cant’ cross the water layer adjacent to the cell
How may a drug be transported across the cell membrane?
I don’t think we need to know this, but included it anyways.
Paracellular transport (water soluble agents)
Diffusion (lipid soluble agents, i.e., antidepressants, nicotine, alcohol)
Protein transporters (i.e., glcuose, amino acids, cyclosporin, gabapentin)
Receptor mediated transcytosis (i.e., insulin, interleukins)
Absorptive transcytosis (i.e., albumin)
Efflux transportation (i.e., cetirizine)
T/ F Rate of absorption is different from extent of absorption
True
T/ F Rate of absorption is determined by the site of administration and the drug formulation (bioavailability)
True
Why is understanding the difference in rate of absorption and the degree of bioavailability important?
Determines how quickly particular drugs reach target concentrations
What is the bioavailability of a drug given IV?
100%
(last slide of week 1 lecture 2: Intro to pharmacotherapeutics and pharmacokinetic concepts)
What is the bioavailability of a drug given IM or SC?
75-100%