Therapeutic Index + Additional Chapter 3 Notes

Therapeutic Index Is the amount of drug that causes a therapeutic effect. Toxicity Adverse Response Therapeutic Threshold response window Desired Response (Not arough) TIME Common signs of drug toxicity may include new onset confusion or disorientation Critical elements of assessment in pt w/ toxicity. ① mental status vitals Pupillary exam. Therapy Drug Monitoring Peak + trough levels (P+t) Done for antibiotics that have a narrow therapeutic range (usually trough) Frequently done for vancomycin; vanco may cause renal failure if drug concentration is too high Vanco: Renal failure is preventable by monitoring trough levels. Dose mod made based on trough Peak Highest plasma concentration (absorption) Antibiotic Concentration Trough: Lowest plasma concentration (elimination) 1 2 3 DOSE Peak: 30-60 mins after infusion complete Trough: Drawn just before next dose of drug Onset, peak, duration ONSET Peak Concentration Onset when drug starts to take effect. Peak: Highest concentration - Maximal therapeutic effect. minimum Effective Concentrations Duration then long lasts. DURATION TIME Side Effects (SE) Secondary drug effects, generally expected, maybe unexpected. Usually mild in nature + self resolve, may be good / bad. BX Good-Minoxidil hair growth. ADR's unexpected, unintended, noxious (harmful / unpleasant); may be serious + require immediate tx. BX Thalidomide CONCENTRATION Interactions, additive, synergistic, + antagonistic effects Interactions When 2 or more drugs react w each other. Ex: Sildenafil - Nitrates (Dramatic hypotension) Additive effects: Sum effect of 2 drugs will ↑ response beyond what either could do alone. Ex: Diuretic + betablocker will antihypertense effect Synergistic (hyperadditive): Effect is SUBSTANTIALLY greater than what drugs can do alone.. Ex: Trimethoprim sulfamethoxazole Weak alone, strong together. Antagonistic: 1 drug reduces / blocks activity of another Ex: Naloxone + Morphine Warfarin + Vitamin K Other Interactions Drug-food interactions Grapefruit, MAOI's tyramine Drug/Lab interactions Digoxin can affect troponin (falsely low = missed MI) Drug-induced photosensitivity: Some drugs make pt. more sensitive to sunlight. Ex: Antibiotics, pyrazinamide Education: Avoid excessive sunlight, sunscreen