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8 Cards in this Set

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Rifampin
- gram +ve bact
- used as a prophylactic antibiotic
- inhibits DNA dependent RNA polymerase => do not take if pregnant
- CYP450 induction: increased metabolism of drugs such as warfarin
- causes orange color to body fluids
- severe GI upset
Quinolones
- also known as "floxacins")- inhibit bacterial DNA gyrase, an enzyme that supercoils DNA.
- They have bacteriocidal activity against gram– bacteria.
- While they are a third choice against gram+ staphylococci, the first-generation quinolones are not effective against gram+ streptococci.
- They have good penetration into bone, soft tissue, and the urinary tract and so are often used to treat osteomyelitis, tissue infections, and UTIs.
Important characteristics of quinolones
1. CYP P450 inhibition
2. Prolongation of the QT interval
3. Binding (chelation) of divalent minerals
4. Crystalluria
5. Lower seizure threshold
6. Hypersensitivity in HIV+ patients
7. Teratogenicity
8. Rupture of Achilles tendon
Important characteristics of quinolones
- CYP P450 inhibition: (First-generation quinolones.) Always look up potential interactions with other drugs given at the same time.
- Prolongation of the QT interval: Quinolones can further increase the QT interval in patients taking other drugs that prolong the QT interval and in patients with hypokalemia or bradycardia.
- Binding (chelation) of divalent minerals: Taking food (dairy, soy), supplements, antacids, containing Ca2+, Fe2+, Mg2+, or Al2+ within 2 hours of a quinolone will prevent absorption of the antibiotic. Sulcrafate (contains Al2+) also prevents absorption of quinolones.
Important characteristics of quinolones
- Crystalluria: Quinolones can precipitate in the urinary tract. Encourage patients to drink eight full glasses of water per day. Patients who experience crystalluria are given sodium bicarbonate to alkalinize the urine and dissolve the crystals. Quinolone doses must be decreased in renal impairment.
- Hypersensitivity in HIV+ patients: Quinolones can cause a toxic shock–like syndrome with a diffuse, nonpruritic rash, fever, and hypotension in patients who are HIV+.
- Teratogenicity: The effects on DNA gyrase place quinolones in Pregnancy Risk Category C. They are also contraindicated in children because they have been shown to cause cartilage toxicity in juvenile dogs.
- Rupture of Achilles tendon: This rare potential adverse drug effect was identified from postmarketing surveillance reports. Patients over age 80 have a reported 20-fold increased risk.
Metronidazole
- Flagyl
- is a broad-spectrum antibiotic that is now recommended by the CDC as the first-line agent against Clostridium difficile (instead of vancomycin).
- is used with tetracycline and amoxicillin in "triple therapy" against Helicobacter pylori, the bacterium that causes peptic ulcer disease.
- is also active against other anaerobic bacteria and parasites
- is used as a topical agent to treat rosacea.
- It is often prescribed to travelers to take in case of "traveler's diarrhea," which is most often due to E. coli and Giardia.
Important points to remember about metronidazole
- Inhibits CYP P450
- Interacts with alcohol
- Inactivates contraceptive steroids
- Teratogenic in first trimester
- Causes red-brown urine
- Neuropathy
Important points to remember about metronidazole
- CYP P450 inhibition: Always look up potential interactions with other drugs given at the same time.
- Interacts with alcohol: Consumption of alcohol during or for 3 days after use of metronidazole will result in a disulfiram-like (Antabuse-like) reaction that includes severe flushing, GI distress, and headache. Patients must withdraw from alcohol before beginning therapy with metronidazole.
- Inactivates contraceptive steroids: As with other antibiotics, women should use another method of birth control during and for 1 month after use of metronidazole.
- Teratogenic in first trimester: Women who may become pregnant should use another antibiotic for bacterial vaginosis (eg, clindamycin cream).
- Causes red-brown urine: Metabolites cause the urine to appear a red-brown color. This is not hematuria. Metronidazole also causes a metallic taste sensation.
- Neuropathy: Neuropathy (numbness, pain, tingling, weakness in the extremities) is a rare but serious potential adverse drug event in patients who take metronidazole as long-term (3 weeks or more) systemic therapy. It takes several months to resolve after discontinuation of the antibiotic.