Recent study in this laboratory is reviewed. Combination of group 4 metallocene dichloride (Cp2MCl2 : M= Zr, Hf) and silver salt (AgX : X = ClO4, OTf etc.) is a particularly effective reagent for activating glycosyl fluoride, which offers a new and efficient method for -glycoside synthesis, which made us to succeed in the first total synthesis of mycinamicin macrolide antibiotics. Mechanistic consideration of this activation led us to find that the reagent combination in 1 : 2-ratio, rather than the original 1 : 1-ratio, of Cp2MCl2 and AgX engendered further enhanced reactivity. Some of the recent application in oligosaccharide synthesis is listed to show the broad scope of this new glycosidation reaction in natural product synthesis. Furthermore, this combinational reagent offers a powerful basis for aryl -glycoside synthesis and the total syntheses of three prototypical compounds of this class, vineomycinone B2 methyl ester and gilvocarcin M and V, were successfully carried out by this glycoside activation method.
It is bactericidal in vitro at peak concentrations equal to or slightly greater than the minimum inhibitory concentration (MIC).
INDICATIONS AND USAGE: TOBI Podhaler is an antibacterial aminoglycoside indicated for the management of cystic fibrosis patients with Pseudomonas aeruginosa.
Safety and efficacy have not been demonstrated in patients under the age of 6 years, patients with forced expiratory volume in 1 second (FEV1)
Increasing the peak, will result in an increased post-antibiotic effect.
Mechanism of Action: Aminoglycosides are rapidly bactericidal.
Streptomycin binds to 30S subunit of the bacterial ribosome,specifically to the S12 protein which is involved in the initiation ofprotein synthesis. Experimentally, streptomycin has been shown toprevent the initiation of protein synthesis by blocking the binding ofinitiator N-formylmethionine tRNA to the ribosome. It also prevents thenormal dissociation of ribosomes into their subunits, leaving themmainly in their 70S form and preventing the formation of polysomes. Theoverall effect of streptomycin seems tobe one of distorting the ribosome so that it no longer can carry outitsnormal functions. This evidently accounts for its antibacterialactivitybut does not explain its bactericidal effects, which distinguishesstreptomycinand other aminoglycosides from most other protein synthesis inhibitors.
Risk factors for Nephrotoxicity: Age, renal insufficiency, elevated trough
concentrations, total daily dose, cumulative dose, concurrent nephrotoxic
drugs, prior aminoglycoside exposure, duration of treatment.
The aminoglycosides are products of species and are represented by streptomycin, kanamycin,tobramycin and gentamicin. These antibiotics exert theiractivity by binding to bacterial ribosomes and preventing theinitiation of protein synthesis.
Levels may be advised more frequently than once weekly in patients exhibiting conditions predisposing them to pharmacokinetic variability such as:
(1) Fluid overload or dehydration
(2) Rises in serum creatinine above baseline of > 0.3 mg/dl
(3) Acute cardiac, and/or renal decompensation.
(4) Severe hypotension (decreased renal perfusion)
(6) Ascites (increased Vd)
(7) Burn patients (usually see increases in kel)
(8) Cystic fibrosis patients (increases in kel)
(9) Surgery patients
Draw levels off the third dose for:
-Patients with normal renal function based on Creatinine/Bun, I/O's, medical history; concomitant drug therapy, and hydration status.
When to draw levels: Aminoglycoside: Peak/trough: 30 minutes before and after a 30 minute infusion.
Draw levels off the first dose for:
- Patients with abnormal renal function based on BUN/SCR; I/O's, edema, history of renal or cardiac disease.
- Patients receiving other nephrotoxic drugs.
- Patient is neutropenic, febrile, and/or unstable.
- Patient has unstable or increasing serum creatinine.
When to draw levels: 1st level: aminoglycoside: 30 minutes post infusion. 2nd level: at least one half-life (depending on drug) after the 1st level.