Intro and Anti-psychotics Flashcards
Pharmacokinetics
How a drug is absorbed, distributed, metabolized, excreted. What the body does to a drug. Liberation, Absorption, Distribution, Metabolism, Excretion.
Pharmacodynamics
Mechanism of action of a drug. What the drug does to the body.
Enteral/Oral administration
via the GI tract: safest, easiest route; must pass through the GI tract (w/stomach acid, enzymes) and enter portal circulation for 1st pass metabolism (1st pass effect)
1st-pass metabolism
absorbed in GI tract, enters portal vein to liver, metabolized, then enters general circulation. eventually sent back to liver by arterial circulation for more metabolism. PO takes 1-3 hours for 75% of dose of most psychoactive drugs to enter blood, depending on lipid solubility.
Parenteral/Inhalation
Avoids GI tract, 1st-pass metabolism, inhaled to lungs. Fastest drug effects (8-10 seconds) b/c lungs have largest surface area, avoids most of 1st-pass metabolism, blood goes from lungs to left side of heart and pumped out to arterial system (to brain very fast).
Why are smoking drugs of abuse (when inhaled) very reinforcing?
Partially due to very fast effects.
Transmucosal
Across mucous membranes, directly into bloodstream. Sprayed into nose/snorted. Drug effects in 2-3 minutes for cocaine.
Buccal (sublabial)
Between cheek and gums (nicotine gum)
Sublingual (SL)
Under tongue (nitroglycerine-for heart pt; alprazolam-xanax)
Intravenous (IV)/Injected
Very fast drug effects (15-30 seconds)
Intramuscular (IM)
Drug effects in 10-20 minutes.
Depot form
Intramuscular (IM): allows slow, controlled release over weeks (e.g., Risperdal Consta, Haldol Decanoate)
Intravenous/IV Advantages
Emergency; Dose titration; Irritating substances when diluted
Intravenous/IV Disadvantages
Risk of adverse drug reactions (ADRs); Cannot give highly lipid drugs; Vein collapse with frequent repetitions.
Subcutaneous (SC, SQ, subcut)
Injected just under skin, not into the vein: Drug effects in 15-30 minutes, or hours to months. Examples: vaccines, insulin, TB skin test.
Subcutaneous Advantages
Better for highly lipid drugs, implantation of solid pellets
Subcutaneous Disadvantages
Possible pain, tissue damage from irritating substances
Transdermal
Through skin by patch
Transdermal Advantages
Slow, controlled release over hours to days
Transdermal Disadvantages
May get irritation, sometimes inconsistent absorption, must avoid heat and rubbing
Transdermal Examples
nicotine patch for addiction, hormonal patches, methylphenidate (daytrana) for ADHD, rivastigmine (exelon) for dementia, selegiline (emsam) for depression, scopolomine for motion sickness
Liberation
release of drug from its dosage form
Absorption
movement of drug from administration site into the blood
Distribution
movement of drug from intravascular to extra-vascular space