infection pharmacology

penicillins

penicillin, amoxicillin, piperacillin tazobactam

destroys bacteria by weakening the bacterial cell wall- bactericidal (kills bacteria)

used for a wide variety of infections, often rx for streptococcus pneumoniae which can cause pneumonia and meningitis, also they work against some gram negative cocci

can be used for prevention against bacterial endocarditis in at risk pts

complications: anaphylaxis, renal impairment, electrolyte imbalance (hyperkalemia and hypernatremia)

contraindications: allergy to penicillin, cephalosporins, or imipenem

always assess for allergy, monitor for s/s of hypersensitivity, monitor IV site, monitor kidneys, tell pts to complete all meds

drug interactions with penicillins

aminoglycosides (IV) and clavulanic acid: additivity; more effective killing of bacteria

methotrexate: decreased renal elimination of methotrexate; increased methotrexate levels

NSAIDs: compete for protein binding; more free and active penicillin ( may be beneficial)

oral contraceptives: uncertain; may decrease effectiveness of contraceptives

probenecid: competes for elimination; prolongs the effects of penicillin

rifampin: inhibition; may inhibit the killing activity of penicillins

warfarin: reduced vitamin K from gut flora; enhanced anticoagulant effect of warfarin

cephalosporins

cephalexin, cefazolin, ceftriaxone, cefepime

similar to penicillins, they destroy bacterial cell wall- bactericidal

broad spectrum antibiotic that treats UTIs, post op infections, pelvic infections, and meningitis

often chosen when a specific bacteria has not been identified

complications: anaphylaxis, bleeding, thrombophlebitis, renal insufficiency, antibiotic associated pseudomembranous colitis (results from overgrowth of C diff, can be life threatening)

do not give to patients allergic to penicillin

no alcohol

cephalosporin drug interactions

ethanol (alcohol): accumulation of acetaldehyde metabolite of ethanol; acute alcohol intolerance (disulfiram like reaction) after drinking alcoholic beverages within 72 hours of taking cefotetan, S/S include stomach cramps, n/v, diaphoresis, pruritus, h/a, and hypotension

antacids, iron: decreased absorption of certain oral cephalosporins (cefdinir, cefditoren); decreased effectiveness of drug

probenecid: decreased renal excretion; increased cephalosporin levels

oral contraceptives: unknown; increased risk for pregnancy

carbapenems

imipenem-cilastatin, meropenem

beta lactam antibiotics that will cause destruction of microorganisms

broad spectrum; used for serious infections like pneumonia, peritonitis, UTIs due to gram positive cocci

often safe for cases where other antibiotics have failed

complications: allergy, GI upset, superinfections (C diff)

interactions: valproic acid (breakthrough seizures are possible)

ask about allergy to other beta lactams, penicillins, or cephalosporins

vancomycin

vancomycin

the big gun antibiotic

destroys bacterial cell walls, causing destruction of microorganisms

tx of serious infections due to methicillin resistant staph, tx of antibiotic associated pseudomembranous colitis due to C diff

complications: ototoxicity, infusion reactions (red man’s syndrome), renal toxicity

interactions: increased risk for ototoxicity when taking vanco with other meds that cause ototoxicity (loop diuretics, furosemide)

monitor kidney labs

infuse slowly (over 1 hr)

vancomycin onset

route: IV

onset: variable- depends on pt condition

peak plasma concentration: 1hr

elimination half life: 4-6hr

duration of action: up to 24hr; longer in renal dysfunction

monitor trough levels to ensure levels are therapeutic but not toxic

tetracyclines

tetracycline, doxycycline

broad spectrum antibiotics that inhibit microorganism growth- bacteriostatic

used for acne, periodontal disease, pneumonia, antrax, lyme disease, GI infections (h pylori)

complications: GI discomfort, tooth discoloration, hepatotoxicity, photosensitivity, suprainfection

contraindications: taking while pregnant can stain unborn baby’s teeth and children under 8

interactions: milk products and antacids (and iron)

do not take with calcium, aluminum, magnesium, or iron

macrolides

erythromycin, azithromycin (z-pack)

slows growth of microorganisms

tx infections in pts with penicillin allergy; resp infections, skin infections, and STIs

complications: GI discomfort, prolonged QT intervals, ototoxicity

contraindications: can not use if pt has liver disease or QT prolongation

metabolized by the liver and can worsen liver dysfunction if liver disease is present

monitor for GI upset- take with food

cardiac hx- monitor for arrhythmias

macrolides reported adverse effects

cardiovascular: palpitations, chest pain, QT prolongation

CNS: h/a, dizziness, vertigo

GI: n/v/d, hepatotoxicity, heartburn, flatulence, cholestatic jaundice, anorexia, abnormal taste

integumentary: rash, urticaria, phlebitis at IV site

other: hearing loss, tinnitus

aminoglycosides

gentamicin, tobramycin, neomycin

bactericidal antibiotics that destroy microorganisms

tx of gram negative bacilli (E coli), gentamicin and tobramycin are common choices for systemic infections such as sepsis or complicated UTIs, oral neomycin suppresses the normal flora of GI tract, tx infections of the eye, ear, and skin

complications: ototoxicity, nephrotoxicity, hypersensitivity

interactions: other ototoxic meds

peak and trough levels

antivirals

acyclovir, ganciclovir

prevents the reproduction of viral DNA

tx of herpes simplex and varicella zoster viruses

complications: phlebitis (if given IV), nephrotoxicity, suppressed bone marrow

interactions: not used in pregnancy and lactation, monitor for toxicity when combined with other meds

herpes simplex = oral/genitals lesions

varicella zoster = chicken pox and shingles

take full course, use barrier contraception, infuse slowly, take with food

antituberculosis (antimycobacterial)

pyrazinamide, rifapentine, isoniazid (selective)

rifampin (broad spectrum)

indicated for active and latent TB

for active TB: 4 med regimen for 6-24 months

for latent TB- 2 med regimen once weekly for 3 months

complications: peripheral neuropathy, hepatotoxicity, discoloration of urine

interactions: not used in pregnancy or liver disease; avoid tyramine foods (aged cheeses, cured meats) and alcohol

2 different forms of birth control due to birth defects

not taken with food- take 1 hour before or 2 hours after meals

take full course

frequent LFTs

do not take with warfarin (coumadin)

airborne disease

monoclonal antibodies

rituximab, pembrolizumab, trastuzumab (…mab endings)

to bind selectively to specific antigens of cells or pathogens without harming healthy tissue

used in oncology, autoimmune diseases, RSV, and alzheimer’s

complications: infusion reactions, fever, tachycardia, hypotension, anaphylaxis, increased r/f infection r/t immunosuppression

interactions: steroids, live vaccines