Chapter 7: Medicines and Pharmacology Flashcards
Drug admin: do not pass through liver first (no first-pass metabolism)
Sublingual and rectal drugs
Drug admin: based on lipid solubility through the epidermis
Skin absorption
Drug admin: restricted to nonionized, lipid-soluble drugs
CSF absorption
Largely responsible for binding drugs (PCNs and warfarin 90% bound)
Albumin
Will displace unconjugated bilirubin from albumin in newborns (avoid in newborns)
Sulfonamides
Where are tetracycline and heavy metals stored?
In bone
Constant amount of drug is eliminated regardless of dose
Zero order kinetics
Drug eliminated proportional to dose
First order kinetics
How many half-lives for a drug to reach steady state?
5
Amount of drug in the body divided by the amount of drug in plasma or blood.
Volume of distribution
Drugs with a high volume of distribution: extravascular vs intravascular concentratoins
High volume of distribution: higher concentrations in extravascular compartment (e.g., fat tissue) compared with intravascular concentrations
Fraction of unchanged drug reaching the systemic circulation
Bioavailability
Bioavailability intravenous drugs
100% bioavailability IV drugs, less other routes (e.g., oral)
Drug level at which desired effect occurs in 50% of patients
ED-50
Drug level at which death occurs in 50% of patients
LD-50
Effect at an unusually low dose
Hyperactive
Tolerance after only a few doses
Tachyphylaxis
Dose required for effect
Potency
Ability to achieve result without untoward effect
Efficacy
Drug metabolism: components of Phase 1
Demethylation, oxidation, reduction, hydrolysis reactions (mixed function oxidases, requires NADPH/oxygen)
Drug metabolism: components of Phase 2
Glucuronic acid (#1) and sulfates attached (forms water-soluble metabolite); usually inactive and ready for excretion.
Def: biliary excreted drugs may become deconjugated in intestines with reabsorption, some in active form
Entero-hepatic recirculation (eg, cyclosporine)
Inhibitors of p-450
Cimetidine. Isoniazid. Ketoconazole. Erythromycin. Cipro. Flagyl. Allopurinol. Verapamil. Amiodarone. MAOIs. Disfulfiram.
Inducers of p-450
Cruciform vegetables. ETOH. Insecticides. Cigarette smoke. Phenobarbital (barbiturates). Dilantin. Theophylline. Warfarin.
Most important organ for eliminating most drugs (glomerular filtration and tubular secretion)
Kidney