3: Pharmacokinetics Flashcards
Three ways to minimize med errors
- Use computerized orders instead of hand written
- Use a bar-code system
- Have a senior pharmacist accompany physicians on rounds
Most common means for drugs to reach their targets
Simple diffusion
Three ways drugs cross the cell membrane and what theyre most commonly used for
- Facilitated diffusion via channels -> drug elim
- Active transport -> drug elim
- Direct penetration -> reaching target tissues
Example of a polar drug
Quaternary ammonium
If pH is lower, what does that mean for a compound in that solution?
Its more likely to have an H attached
Only way weak acids and bases can cross a membrane
In their unionized form
Values for both S (salt factor) and F (bioavailability)
Less than 1
When does Vd become large and “apparent”?
When there is a lot of drug in the body, but not in the plasma
Examples of non-Microsomal enzymes in phase I of biotransformation
Esterases, alcohol dehydrogenases, oxidative deaminases, decarboxylases
Inducers vs inhibitors for cytochrome P450 enzymes
Inducers: increase enzyme levels -> speed up metabolism of other drugs
Inhibitors: inhibit the enzyme -> slow metabolism of the drug
Examples of inducers and inhibitors of cytochrome P450
Inducers: phenobarbital, carbamazepine, ethanol, cigarette smoke
Inhibitors: erythromycin, ketoconazole, metronidazole, grapefruit juice
Which specific cytochrome P450 is inhibited by grapefruit juice?
P450 CYP3A4
What does first pass metabolism do?
Greatly decreases bioavailability of orally administered drugs
Excretion rate
Mass eliminated per unit time
Clearance
Plasma volume from which all solute is removed per unit time (a flow rate)
Tachyphylaxis
Rapid tolerance to a drug
Idiosyncrasy
An unusual response to a drug due to inherited alteration, often an enzyme defect
Why are adverse drug reactions more likely in elderly
- Drug accumulation due to declining renal function
- Greater severity of illness
- Use of drugs with low therapeutic index
- Poor compliance
- Presence of multiple pathologies
- Inadequate supervision
Three possibilities in a drug-drug interaction
- Intensification of effects
- Reduction of effects
- Creation of a unique response
Common adverse drug effects
Constipation, skin rash, diarrhea, dizziness, drowsiness, dry mouth, HA, insomnia
What can food impact in terms of drugs?
- Absorption
- Metabolism (ex: grapefruit juice)
- Drug toxicity
- Drug action
- Timing of drug admin
Examples of drugs that can lead to liver failure
- Lipid lowering drugs
- Antiseizure drugs
- Drugs for Tb
- Antiretroviral drugs
- Oral hypoglycemics
- Anti fungal drugs
- Immunosuppressants
- Acetaminophen
Common heart condition caused by 100+ drugs
QT prolongation
Three characteristics for calling something a teratogen
- Characteristic malformations
- Acts during a specific window of vulnerability
- Incidence increases with dose and duration of exposure
