Question | Answer |
Bactrim, Septra (Trimethoprim+Sulfamethoxazole) | SMX – structural analogue of PABA; blocks production of folic acid
TMP – DHFR inhibitor that blocks the conversion of DHF to THF.
Together this combination produces a synergistic effect |
Bactrim, Septra (T+S) PK | Distributes to most tissue/fluid including the CSF & prostate
Needs renal adjustment b/c cleared by kidney |
Bactrim dosing | 5:1 ration of SMX to TMP. Dosing based on TMP
80TMP:400SMX is reg. strength tab
160TMP:800SMX is dbl strength tab
16TMP:80SMX/ml IV. Every 10ml IV is like a dbl-strength tab.
KNOW HOW TO CONVERT FR ml IV to mg PO!
Oral dose is BID. IV is Q6h |
Bactrim (Septra) SoA | G+: S. pneumo, not for DRSP; MSSA, Listeria, CA-MRSA on SKIN ONLY (NOT IV HA-MRSA pneumo)
G-: E. Coli, UTIs, COPD (H. influ, M. catarrhalis, Kleb)
Septra is #1 for: S. maltophila, B. cepacia, Toxoplasmosis, Prostatitis, Shigellosis, CA-MRSA, Nocardi |
Bactrim dosing (cont'd) | Usual dose: 1 DS BID
PCP prophylaxis is 1 DS TIW |
Bactrim ADRs | NV
Insoluble, crystallization
sun sensitivity -> rash/allergy
hypo/hyperglycemia
hyperK with IV
Pancreatits, Hepatitis
Blood dyscrasias
teratogenic |
Bactrim DDIs | Warfarin: check INR (increases) - more bleeds
MTX (methotrexate) is displaced
Increases hypoglycemic effect of sulfonylureas |
Clindamycin (Cleocin) PK & MoA | Static, 50s ribosomal protein synthesis inhibitor
Penetrates most tissue well except CSF
Accumulates in Segs/Macs and in abscessed tissue
Above diaphragm anaerobic agent
Main antibiotic implicated in C. dif colitis |
Clindamycin SoA | Oral anaerobes, abscess
Abdominal C. diff, C. perfringens, and B. Fragilis
Used topically for acne
If PCN allergy, good for Staph, MSSA, Strep
G. vaginalis (G- rod, facultative anaerobe, vaginitis)
dental prophy
NOT for enterococcus |
Clindamycin ADRs | AAD (C. diff)
Metabolizes to benzyl alcohol. If used in kids, monitor conc to avoid seizures.
Bitter taste
Prolongs NMJB (neuromuscular junction blockers) - reverse w/ pancuronium
Dizziness & HA |
Metronidazole (Flagyl) PK & MoA | Mainly used for anaerobes BELOW diaphragm (but active above as well.
Cidal mostly
No activity against aerobes (req anoxic pore to enter organism)
Penetrates all tissues and fluids |
Metronidazole (Flagyl) SoA | Best for anaerobic C. diff, B. frag IA infections
Trichomonas, Giardia, Entamoeba, Gardnerella, H. pylori |
Metronidazole (Flagyl) | Contraindicated in pregnancy and nursing moms
nasty metallic taste (take with snack)
Dizziness, HA, rarely -seizures, neuropathy, tingling, numbness
Pancreatitis
dark urine |
Metronidazole (Flagyl) interactions | Warfarin (increased conc. more bleeding risk)
Alcohol (disulfiram rxn like Antabus) *Avoid in alcholics!
Light - degrades Flagyl and makes it browner |
Nitrofurantoin (MacroBID, Macrodantin) uses & SoA | UTI Tx or prophylaxis
E. coli, S. sap, E. faecalis, Group B Strep (prenatal) |
Nitrofurantoin (MacroBID, Macrodantin) MoA & PK | Binds to ribosomal protein, damages DNA
May antagonize quinolone activity when Tx G-
absorbed in small intestine
Excretion decreases in proportion w/ ClCr decreases
Macrocrystal helps w/ absorption. Causes dark brown feces
Not given to kids |
Nitrofurantoin (MacroBID, Macrodantin) ADRs | Pulmonary rxns (asthma-like, SOB, fibrosis)
Diarrhea
Elevated LFTs
G6PD deficiency -> anemia
peripheral neuropathy
discolors urine orange/brown |
Colistin (Colistimethate sodium, Coly-Mycin) MoA & PK | Cidal
Cationic polypeptide polymixin - detergent-like mechanism which interferes with cytoplasmic membrane of G- organisms
Removed by GFR almost completely unchanged
Concentration dependent |
Colistin SoA | G-: mostly used for MDR (multidrug resistant) Pseudomonas, Kleb, Acinetobacter, Enterbacteria, E. Coli
Proteus, Providencia, Serratia, Burkholderia, Stenotropheomonas
Only drug that works for NMD1 beta-lactamases!!
NOT for anaerobes |
Colistin ADRs | nephrotoxicity
neurotoxicity
respiratory arrest, apnea (breathing cessation) w/ IM due to NMJ blockade
SEs worse w/ renal dysfxn |
Metronidazole dose for Trichomoniasis | 2g x single dose |