Basic Pharmacology Flashcards
Pharmacokinetics
How a drug is absorbed, distributed, metabolized, and excreted
Pharmacodynamics
Mechanism of action of a drug
Routes of Administration
Oral (PO)
Enteral
Route of administration via GI tract Includes Oral (PO) and Rectal (PR) Safest and easiest route Least expensive Must pass through GI tract (w/stomach acid, enzymes) & enter portal circulation for 1st-pass metabolism (1st-pass effect)
What is the safest, easiest, and least expensive route of administration for medication?
Enteral aka oral (PO)
Hepatic Portal Vein
A short vein that transports blood containing the medications, etc. to the liver for 1st-pass metabolism, before it’s filtered back into the general circulation
1st-pass metabolism
Absorbed in the GI tract, enters portal vein to liver, metabolized, then enters general circulation
2nd-pass metabolism
Eventually sent back to liver by arterial circulation for more metabolism
Generally speaking, how long does it take once you take a pill to get a peak plasma level so that it can get to the brain?
~ 60 minutes
Parenteral
Route of administration avoiding the GI tract and hepatic 1st-pass metabolism
How long before the drug is distributed throughout the system via inhalation?
8 seconds
Smoking and inhalant drugs of abuse are very reinforcing partially due to _____?
The very fast effects on CNS (about 8 seconds)
Transmucosal
Across mucous membranes directly
What are some of the methods of transmucosal administration?
Buccal or sublabial (e.g. nicotine gum)
Sublingual (SL) [e .g. nitroglycerine, alprazolam (XANAX)]
Sprayed into nose or sniffed (e.g. drugs of abuse and nasal decongestants)
What are the methods of injection administration?
Intravenous (IV) or Intra-atrial (IA)
Subcutaneous (SQ or SC)
Intramuscular
Epidural
What is the rate of dispersion for IV injection?
Very fast, seconds, but not as fast as inhalation
What is the rate of dispersion for subcutaneous injection?
Hours, days, months
What is the rate of dispersion for intramuscular injection?
~ 15 minutes
Depot form
Type of intramuscular injection, allows for slow, controlled release (e.g. Risperdal Consta, Haldol Decanoate)
Epidural
Injection into area just outside dura mater (outer layer of the meninges that surround CNS)
Used for chronic pain and childbirth
What are the types of parenteral administration?
Inhalation, injection, transmucosal, transdermal,
Transdermal
Type of
LADME
Liberation Absorption Distribution Metabolism Excretion
Liberation
release of drug from its dosage form
Absorption
movement of drug from administration site into the blood
Distribution
Movement of drug from intra-vascular to extra-vascular space
Metabolism
transformation of drug into compounds that are easier to eliminate (e.g. liver wants to make compounds more water soluble so that they can be excreted in the urine)
Excretion
elimination of drug or metabolite via renal, biliary, or pulmonary processes
Why are some drugs enteric coated?
Decreases irritation to stomach lining
Delays absorption until the intestine for those drugs that are better absorbed in the intestine (which is more alkaline than the stomach)
Particularly useful for those drugs that are either poorly absorbed or destroyed in acidic environment)
What is the bottom line of liberation and absorption?
TAKE DRUGS AS INSTRUCTED
Why are some drugs instructed to take on empty stomach?
Many drugs are absorbed better in stomach than the intestine (and vice versa)
Reaches desired concentration levels faster when taken on an empty stomach
What are some technologies for controlling release and absorption?
Sustained-release Sustained-action Extended-release Controlled-release Time release technology
What is the point of developing these technologies for controlling release and absorption?
To spread out the action of the drug, decrease side effects, and in general, make drugs more convenient to take (especially in children and stimulants)
Cytochrome P450 (CYP)
System in the liver that is the main system of enzymes that inactivate drugs
What are the most important CYP enzymes?
1A2, 2C9/19, 2D6 (30%), 3A4 (55%)
Three different groups of metabolizers
Poor (PM)
Rapid or extensive (i.g. normal)
Ultra-rapid (URM)
Different ethnic/racial groups vary in certain these enzymes, leading to ___________
varying degrees of metabolism and effects
What are some considerations that you need to make with elderly population?
- Overall, may be twice as sensitive to drugs, so the dose needs to be halved, usually
- Polypharmacy is common, thereby leading to many drug-drug interactions
What are some changes that influence metabolism in the elderly?
- Decreased hepatic (liver) & renal (kidney) function
- May have less effective barriers to absorption (GI, blood-brain-barrier)
- May have increased body fat
- May have more sensitive receptors
- Hepatic changes (decreased CYP2C19, hepatic mass, and circulation)
What are some sex differences to consider with medication metabolism?
- Females may have more sensitive receptors
- Possible hormone interactions
- Combined with phamacokinetics factors (e.g. more body fat, lower body weight), females may be twice as sensitive as males (dose may need to be halved)
What are the factors involved in inter-individual variability?
- Genetics (PM vs RM vs URM)
- Age
- Sex
- Environmental factors
- Disease
Types of DDI’s
Additive
Synergistic
Antagonistic
Pharmacokinetic