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Aminoglycoside

Aminoglycoside. Ahmad Noor, PharmD. Aminoglycosides are a group of antibiotics that are effective against:. Mechanism of action & pharmacokinetic:. MOA : They bind to ribosomal units ( 30S-50S ) in bacteria & inhibits protein synthesis Pharmacokinetic :.

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Aminoglycoside

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  1. Aminoglycoside Ahmad Noor, PharmD

  2. Aminoglycosidesare a group of antibiotics that are effective against:

  3. Mechanism of action & pharmacokinetic: • MOA :They bind to ribosomal units ( 30S-50S ) in bacteria & inhibits protein synthesis • Pharmacokinetic : • PO poor absorption; IM or IV best • Distribution: hydrophillic, poor CSF, cross placenta • Metabolism : • Excreted unchanged, special dosing for renal failure

  4. Special concern in treatment: • Tobramycin is superior to gentamicin for ttt of P.aeruginosa . • Gentamicin is the preferred AGL used in combination ttt of enterococcal endocarditis ( with ampicillin or vancomycin). • Streptomycin has the greatest activity of all the AGL against M.tuberculosis. • Capreomycin is an AGL use as alternative drug to ttt mycobacterial infection • Streptomycin & gentamicin are drugs of choice to ttt tularemia • Streptomycin is drug of choice to ttt plague & brucellosis

  5. Single Daily Dose (SDD) of AGL: • For Adult: • There are two main principles for the use of the SDD of AGL: • Since the AGL bactericidal effect is related to peak concentrations, higher doses will achieve a higher peak concentration and ensure efficacy of therapy. With this dosing, it is possible to achieve the desired peak:MIC ratio. • SDD may reduce the frequency of nephrotoxicity since low or undetectable trough concentrations will be attained. • Dose ranges from 3 to 7mg/kg/day for gentamicin & tobramycin. • For children: • The use of SDD of AGL in children has some limitation because of: • Rapid AGL clearance. • Unknown duration of post-antibiotic effect. • Safety concerns. • Limited clinical and efficacy data.

  6. Single Daily Dose of AGL: cont. • SDD relatively contraindications : • S.aureus or Enterococcal infection. • Bacterial pneumonia with pathogen having high MIC. • Toxicity with SDD: • Endotoxin like reactions with SDD AGL’s therapy: - many patients develop rigors, fever, tachycardia. • Ototoxicity: develop vestibular dysfunction with high dose. • Nephrotoxicity decreased with the use of SDD AGL’s. • N.B: • SDD of AGL not for every infection, pathogen, or patient. • Must have therapeutic goal based on pathogen susceptibility & location of infection. • PK’s remain useful tool to screen patients & to establish desired Cpx:MIC ratio.

  7. Aminglycosides dosage : • AGL dose depend on IBW & cretinine clerance. IMP. Formulae: • Creatinine clerance: = (140-age)(IBW in kg) / (72)(Scr)=ml/min x 0.85 for CrCl of women . • Ideal Body Weight (IBW): males: 50kg + 2.3kg per inch over 5’= weight in kg females: 45kg +2.3kg per inch over 5’= weight in kg • Obesity adjustment : use if Actual Body Weight (ABW) is >30% above IBW. To calculate adjusted dosing weight in kg : IBW+ 0.4 (ABW-IBW) = adjusted weight .

  8. Aminglycosides dosage : cont. • SARUBBI-HULL NOMOGRAM FOR AMINOGLYCOSIDES: • General dosing information:The following dosing chart by Sarubbi-Hull (Ann Intern Med 1978; 89: 612-8) may be used to provide the clinician with an initial loading dose and maintenance dose regimen in adult patients. Further dosage adjustments should be individualized and based on peak/trough serum concentrations, which should be drawn after the 3rd maintenance dose.

  9. Aminglycosides dosage : cont. 1- Select loading dose ( based on IBW ) to provide peak serum concentration in the range listed below for the desired AGL:

  10. Aminglycosides dosage : cont. 2- Select maintenance dose ( as % of loading dose ) to maintain peak serum conc. Indicated above according to desired dosing interval & the patient corrected CrCl:

  11. Side effects: • Nephrotoxicity • Risk of Nephrotoxicity with Cyclosporine , Vancomycin , Ampho B , Radiocontrast & NSAIDs . • Risk of nephrotoxicity by once-daily dosing method. • Ototoxicity , deafness • Risk of ototoxicity with loop diuretic . • Risk of nephro/ototoxicity with Cis platinum . • Pseudomembrane colitis • Neuromuscular toxicity • Other drug-drug interactions: • Neuromuscular blocking agents apnea or respiratory paralysis • Non-polarizing muscle relaxant apnea • Oral anticoagulants prothrombin time Note:there is no known method to eliminate risk of AGL nephro/ototoxicity .proper Rx attempts to the % risk.

  12. Follow up & monitoring : • Monitor patient for ototoxicity : tinnitus, vertigo, hearing loss • the drug should be stopped if tinnitus occurs. • Monitor patient for nephrotoxicity periodically .if serum creatinine increases by more than 50% over baseline value it may be advisable to discontinue drug ttt & use less nephrotoxic agent. • Monitor neuromuscular function when administering the drug IV. Too rapid administration may cause paralysis & apnea.Have Ca gluconate or pyridostigmine available to reverse such effect • Monitor patient's neurologic status if the drug is given for hepatic encephalopathy .

  13. Contraindications: • Hypersensitivity to AGL • Pregnancy (AGL is class D during pregnancy ) • Myasthenia gravis • Parkinsonism (AGL may cause neuromuscular blockade, resulting in further skeletal muscle weakness ) • Fetal eight nerve damage ( AGL may cause auditory and vestibular toxicity )

  14. Patient counseling : • Do not take AGL if you are pregnant or could become pregnant during treatment. • Do not take AGL if you are breast-feeding a baby. • Take each dose with a full glass of water. • Take AGL with food. • Store AGL at room temperature away from moisture, heat, and direct light.

  15. References : • Joel Hardman, Lee Limbird, Alferd Goodman Gilman, eds. The Pharmacological Basis Of Theraputics.10th ed. Mcgraw-hill;2001;p1219-1238. • Seymour Ehrenpreis, Eli Ehrenpreis, eds. Clinician’s Handbook Of Prescription Drugs.1st ed. McGraw-hill; 2001;p959-960. • David Gilbert, Robert Moellering, George Eliopulos, Merle Sande, eds. The Sanford Guide To Antimicrobial therapy. 35th ed. Antimicrobial Therapy, Inc;2005;p47-53. • Simeon Marglis, Rodney Friedman, Thomas Dickey, Jermy Birch, eds. The Johns Hopikins Consumer Guide to Drugs.1st ed. Medletter associates, Inc;2005;p766. • Frederic Vagnini, Barry Fox, eds. The Side Effects Bible.1st ed. Random House, Inc;2005;p499-500. • http://health.yahoo.com/drug/d00014a1. • http://www.rxlist.com/cgi/generic2/streptomycin.htm. • http://www.medscape.com/viewarticle/448281_print. • http://bmj.bmjjournals.com/cgi/content/full/312/7027/338. • http://depts.washington.edu/druginfo/Formulary/Aminoglycosides.pdf#search='aminoglycosidenomogram.

  16. Thank You Ahmad Noor , PharmD

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