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Drug/bug pair: Nafcillin (a PCN)
treats: MMSA (methicillin sensitive staphylococcus aureus)
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Drug/bug pair: Amoxicillin (an aminopenicillin)
treats: H. influenzae
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Drug/bug pair: Piperacillin (a ureidopenicillin)
treats: pseudomonas
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What drugs act against cell walls?
Penicillins and cephalosporins. (both have beta-lactam groups)
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When should a pt's allergies be assessed?
Before ever administration of antibiotics/antifungals.
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What penicillins should ONLY be given IM?
Procain penicillin and benzathine penicillin.
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Important facts about hypersensitivity reactions.
- Non-dose related (aka allergy)
- closely monitor for 15-30 min after initial dose of PCNs, esp for rash/urticaria
- thrombocytopenia may occur
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Important facts about direct tissue toxicity.
- Dose related (can occur to anyone if dose is high enough).
- Monitor for twitching/seizures (often seen in pts who receive large doses of anti-pseudomonal PCNs who can't eliminate drug)
- High doses may decrease ability of platelets to function properly resulting in bleeding tendencies (count is normal)
- Procaine PCN may cause acute psychotic rxns.
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Patient related variables important to PCNs
- allergy to PCN or cephalosporin
- renal dysfunction
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Which generations of cephalosporins work against pseudomonas?
Third (only ceftazidime) and fourth generations.
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What are common clinical uses of cephalosporins?
- - most community-aquired and nosocomial infections (due to wide range of activity)
- - CNS infections (3rd and 4th gens only)
- - skin infections (1st gen esp)
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Toxicity concerns related to cephalosporins.
- - hypersensitivity/allergic reactions (non-dose related) - approach is same as for PCNs (monitor for rash/urticaria 15-30 min)
- - direct tissue toxicity (dose related) - same as PCNs (twitching/seizures/poor platelet function)
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Administration considerations for cephalosporins.
- - assess for allergy prior to administration
- - monitor for phlebitis at site of injection
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What antibiotic should be considered for hightly resistant organisms or pts at risk for highly resistant organisms?
- Carbapenems.
- Broad spectrum: gram +/-, anerobes
- No atypical coverage (mycoplasma, Legionella, chlamydia)
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Toxicities of Carbapenems.
seizures (decrease seizure threshold)
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Drug/bug pair: azithromycin
treats: mycoplasma (an atypical)
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What are atypical organisms?
mycoplasma, Legionella, and Chlamydia pneumonia
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What drugs are macrolides?
erythromycin, clarithromycin, and azithromycin
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Drug/bug pair: azithromycin
treats: Chlamydia (and mycoplasma)
better than Doxycyclin because of short course of treatment (despite increased cost)
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Toxicities of macrolides (eryth, clarith, and azith)
- primarily dose related
- GI - D/N/abdominal pain (esp with eryth)
- prolongation of QT interval (less with azith)
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Drug interactions with macrolids (eryth, clarith, azith)
Theophylline, carbamazepine, cyclosporine (clearance is reduced due to interaction with p450 enzyme).
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Drugs that are fluoroquinolones.
ciprofloxacin and levofloxacin
- cover all atypicals (Legionella, chlamydia, mycoplasma)
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Toxicities of fluoroquinolones.
- - cartilege damage in beagles, not recommended in children (except cipro for tx of gonorrhea in adolescents)
- - tendonitis and tendon rupture (stop drug if pain develops)
- - decreased seizure threshold
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Trimethoprim plus sulfamethoxazole
- aka bactrim (a sulfonamide)
- treats: otitis media when ampicillin resistant influenza is suspected; community and hospital aquired infections, good MRSA activity
- does not treat streptococcal (no coverage)
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Drug/bug pair: trimethoprim plus sulfamethoxazole (bactrim)
treats: pneumocystis carinii (PCP)
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Administration consideration for sulfonamides.
- - maintain adequate fluid intake to prevent crystaluria
- - displacement of bilirubin may lead to kernicterus in newborns (avoid use in pregnacy/breastfeeding/infants <6wks)
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Toxicities of trimethoprim (in bactrim)
- megaloblastic anemia (sx of folic acid deficiency); treat with folinic acid
- hyperkalemia and renal insufficiency (esp when treating PCP)
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Drug/bug pair: metronidazole (flagyl)
treats: c.diff (and trichomoniasis)
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Drug/bug pair: metronidazole (flagyl)
treats: trichomoniasis (and c.dif)
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Administration considerations for metronidazole:
Do not infuse iwht other IV drugs if possible.
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Toxicities of metronidazole:
- nausea
- antabuse-like effects (inhibits alcohol dehydrogenase)
- interacts with warfarin
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Drug/bug pair: clindamycin
Staph (including MRSA)
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Toxicities of clindamycin.
Psudomembranous colitis: diarrhea involving superinfections of C.dif which produces a toxin. Treat wiht oral metronidazole or vancomycin.
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Aminoglycosides
- ex. gentamycin
- used for wide range of aerobic gram-neg organims (serious, usually nosocomial)
- poorly absorbed orally
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Toxicities of aminoglycosides:
- - nephrotoxicity (monitor serum creatinine)
- - ototoxicity (cochlear or vestibular)
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Drug/bug pair: vancomycin
treats: MRSA - methacillin resistant staph aureus
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Administration considerations for vancomycin.
- Not absorbed orally (oral therapy only effective for c.diff colitis)
- Give IV doses slowly to avoid hypotension.
- IM route causes tissue necrosis.
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Toxicities related to vancomycin.
- Nephrotoxicity (at concentrations >20mg/dl)
- phlebitis
- red man's syndrom (histamine rxn to too fast administration, prevent w/benadryl)
monitor troughs (correlate to efficacy and toxicity)
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Tetracyclines
- treats: STIs (gonorrhea, syphilis) and acne
- give with full glass of water
- dairy/iron/antacids decrease absorption
- may have dental effects in children (do not use for <8y/o)
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Chloramphenicol
- antibiotic
- treats: salmonella, PID/chlamydia
- be very careful with dose
- monitor for blood dyscrasias: RBC then WBC then platelets decrease
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