Pharmacology Flashcards
Pharmacology
the study or science of drugs (the broad umbrella)
Pharmaceutics
- how the form of the dosage affects the body (i.e. liquid vs tablet)
- Form determines the rate of drug dissolution and absorption
Pharmacodynamics
- how the drug changes the body
- Mechanism of drug action (alter enzyme activity, interact w/ receptors, altering metabolic & chx processes)
- R’ship between drug concentration and body’s responses
- Drug receptor relationship: agonist, partial agonists, antagonists, response & receptors (target sites)
Pharmacotherapy
the use of drugs to prevent or treat disease
Therapeutic:
- what disease the drug is able to treat
- What we would explain to patient “this pill will help treat Hypertensionwhat disease the drug is able to treat
Pharmacologic:
- mechanism of action, how the drug produces its effect
- The chemistry behind how the drug does what it does
Ex: furosemide is a loop diuretic and inhibits reabsorption of Na+ from loop of Henle, thereby ↑ excretion of H2O (you’re going to pee more)
Pharmacokinetics
- study of drug mvt throughout the body
- what the body does with the drug after it is administered)
- Includes 4 processes: Absorption, Distribution, Metabolism, Excretion
Distribution
- refers to the transport of a drug by the BS to its site of action
- drug movement around body after absorption
- Heart, liver, and kidneys receive greatest blood supply=highest exposure to drugs after absorption
- Some drugs bind to proteins (especially Albumin) and form drug-protein complexes
- Only unbound or free drugs can reach target cells
Metabolism: AKA biotransformation
-the biochemical alteration of a drug into an inactive metabolite
-inactive metabolites lack pharmacologic activity and are simply drug waste products awaiting excretion from the body
Liver is the primary site of metabolism
-First-pass effect: drug enters hepatic portal circulation toward liver before reaching target site during metabolism (drug will no longer be 100% bioavailable)
Prodrug-more active after it passes through liver
Excretion
- how drug leaves body (urine, fecal matter)
- Primary elimination by kidneys
- Drugs have undergone extensive biotransformation
- Only small fraction is the original compound when excreted
- kidney pts. may be at risk for toxicity if they cannot excrete metabolites
Bioavailability
- extent to which active drug ingredient is absorbed and is available at target site to produce therapeutic effects
- First-pass reduces bioavailability of the drug to >100% (except prodrug)
- IV, parenteral administered to BS bypasses lover and is 100% bioavailable
Why are knowing about First-pass effect and bioavailability important considerations for drug administration?
-don’t want pt. to OD, toxicity
-know how quickly and predict when effects of drug will be produced
-Geri pts. have slower metabolism, certain meds will work differently for them (pay attention to vitals is HR, RR, BP ok?)
Impact of polypharmacy
Longevity=more illness and ↑ need for medications
Individual specialists prescribing multiple medications; ↑ possibility for AE and D-D interactions
Included in polypharmacy: OTC’s, herbal products, and dietary supplements
Dosing variations for the elderly:
1/2 to 1/3 of standard adult dose
Start low and go slow
↑ dose based on response
Look at geriatric dosing recommendations in drug guide before administering
Pharmacokinetic variables:
Onset of action
Time required to elicit a therapeutic effect
Pharmacokinetic variables:
Duration of action
The amount of time the drug remains in therapeutic range
Pharmacokinetic variables:
Peak
Reaches maximum therapeutic response
Pharmacokinetic variables:
Half-life
Length of time required for plasma concentration to decrease by half (after drug reaches peak, how long it takes to be excreted)
Pharmacokinetic variables:
Receptor
Reactive site, either on the surface or inside the cell
Pharmacokinetic variables:
Drug receptor interaction
The joining of the drug molecules w receptor site
Pharmacokinetic variables:
Natural chemical
Chemical produced by the body, fits into receptor site causing normal cell activity. I.e. Endorphins (stress, fear, pain) interact mainly w/ receptors cell found in regions of the brain responsible for blocking pain and controlling emotions
Agonist
Similar to natural chemicals and have the ability to mimic similar response
- a drug that binds to a receptor & and produces a response is an agonist. The better the fit (into the receptor) the better the response
- Drug w best fit will elicit greater response from ₵ or tissue
Ø Example: Morphine is an agonist. Binds to m-receptor site to block pain
Partial agonist
less efficient response, i.e. Subitex used to treat opioid dependence and has weaker less efficient response than morphine
Antagonist
revent agonist from binding at the site, has no inherent activity
Ø Its effects are caused by lack of agonist action
Ø Can be drug or natural chemical
Ø Competes for binding sites w agonists
Ø Blocks receptor site and natural chemical cannot bind
Ø Can be used when body is producing too much of a response from endogenous chemical or drug OD, I.e.: morphine m-receptor affinity= sedation, naloxone is an agonist to morphine and blocks m sites (in cases of morphine OD)
Food-drug interactions:
Ø Therapeutic response of a drug may be affected by certain foods.
Ø May prevent drug from working the way they should
Ø Can cause side effect that worsen or increase drug effect
Ø Can cause new side effects
Ø I.e. grapefruit juice blocks enzymes in the small intestine needed to metabolize several drug categories can lead to AE & ↑ toxicity
Ethnic and cultural factors influence on pharmacotherapy:
Ø Dietary consideration can increase/decrease therapeutic effect of drugs
Ø Need to be aware of these and how assess how Tx plan should be modified
Ø I.e. Asians may want to use acupuncture and herbal remedies
Ø African Americans may want to pursue religious beliefs
Drug polymorphism
concept that seeks to understand how pharmacotherapy affects different individuals from different ethnic backgrounds
Ø Renin: enzyme that stimulates vasoconstriction and causes BP to be elevated. African Americans metabolize renin differently and may require more than one drug to manage HTN
Asian Americans are “slow metabolizers” of certain drugs such as antianxiety meds and can lead to AE so lower doses should be considered
