glycopeptides mark johnson, pharm.d., bcps associate professor and director of postgraduate...
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Glycopeptides
Mark Johnson, Pharm.D., BCPSAssociate Professor and Director of
Postgraduate Education
Vancomycin—A glycopeptide
http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=1399
Vancomycin
• Mechanism of action– Inhibits cell wall synthesis by binding to the D-Ala-D-Ala
terminus of of peptidoglycan pentapeptide, which as a result inhibits transglycosylase, preventing peptidoglycan elongation and cross-linking
• Mechanism of Resistance: modification of D-Ala-D-Ala binding site (D-Ala is replaced by D-lactate), and thus vancomycin cannot bind to its target site
Vancomycin• Spectrum of Activity– Gram + organisms only (Staph and Strep); particularly
Staphylococci (MRSA), penicillin-resistant Streptococcus pneumoniae
– Synergistic in vitro with gentamicin and streptomycin against Enterococcus faecium and Enterococcus faecalis
– Increased incidence of VRE, but otherwise good coverage against enterococcus
– Vancomycin Resistance: VISA (GISA), VRSA– Kills Staph slowly compared to beta-lactams– Bacteriocidal
Vancomycin• Clinical Use– PO for C. difficile colitis – IV for everything else (usually serious infections including
bacteremia, endocarditis, meningitis)– Also an alternative for PCN allergic patients
Vancomycin
• Pharmacokinetics– Poorly absorbed from GI tract– Widely distributed with Vd 0.4-1L/kg; CSF levels 7-
30% of serum levels with meningeal inflammation; lung tissue 5-41% of serum levels
– Þ-distribution phase 30min; ß-elimination half-life 6-12h
– 90% excreted by glomerular filtration
Vancomycin• Adverse Effects: – Nephrotoxicity (uncommon, but ? Increasing incidence)
and Ototoxicity (rare--possibly related to very high trough conc)• More common with older preparation (“Mississippi
mud”)• Toxicity may be increased with other nephro/oto-toxic
drugs
Vancomycin• Adverse Effects: – “Red man” or “red neck” syndrome • Infusion-related flushing reaction caused by release of
histamine• Prevented by increasing the infusion time
– Phlebitis – Rash– Chills– Fever
Vancomycin
• Dosing– 15-20mg/kg (as actual body weight) every 8-
12h for most patients with normal renal function when MIC < 1
– Dose modify interval depending on renal impairment
– In seriously ill, LD 25-30mg/kg can be used to facilitate rapid attainment of target trough
– Goal AUC:MIC >400 overall; not achievable if MIC > 2 with conventional dosing
AJHP 2009;66:82-98
Vancomycin
• Monitoring: – Troughs most accurate and practical for
monitoring efficacy– Trough historically 5-10mcg/ml, now
>10mcg/mL because of MIC creep– Complicated infections (endocarditis,
osteomyelitis, meningitis, HAP caused by Staph aureus): trough 15-20mg/L
– Scr periodically
AJHP 2009;66:82-98
Vancomycin
• Dosage Forms:– Capsules (Vancocin®) 125mg and 250mg– Injection • Premixed: 500mg (100ml); 1g (200ml)• Powder for reconstitution: 500mg, 1gm, 5gm, 10gm
Telavancin (Vibativ™)Theravance
• Lipoglycopeptide antibiotic (synthetic derivative of vancomycin) for the treatment of complicated gram-positive skin infections
• MOA: inhibits bacterial cell wall synthesis and disrupts bacterial cell membrane function
Televancin vs. Vancomycin
Telavancin (Vibativ™)Theravance
• Antimicrobial Activity:– MSSA, MRSA– Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus
pneumoniae (incl. penicillin resistant), Streptococcus angiosus group– Enterococcus faecalis– Not VRE, not VRSA, maybe GISA– PAE of up to 6 hours
• Efficacy:– Skin and Skin Structure: comparable to
vancomycin and anti-staphylococcal penicillins– HAP: comparable to vancomycin
Telavancin (Vibativ™)Theravance
• ADR’s:– >10%: taste disturbance, n&v, foamy urine– Renal dysfunction: 3% (vs. 1% vancomycin) (monitor renal
function before/during therapy)– Possible: QTc prolongation, Red-man syndrome– Pregnancy C: reduced fetal weights, digit/limb deformities in
animals (need to do pregnancy test)• Drug Interactions:
– Is a CYP3A4 inhibitor, so potential exists– Can interfere with PT, INR, aPTT, ACT, factor Xa as binds to
artificial phospholipid surface—collect samples when telavancin is at trough
Telavancin (Vibativ™)Theravance
• Dosing:– 10mg/kg Q24h IV over 60min
• CrCl 30-50ml/min: 7.5mg/kg Q24h• CrCl 10-29ml/min: 10mg/kg Q48h• CrCl < 10ml/min: insufficient data• Severe hepatic impairment: unknown
– No level monitoring• Cost:– 750mg vial: $150– 250mg vial: $50
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