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Antibiotics basics for clinicians


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  • 1. Dr. LokeshGargM.B.B.S. M.D.
  • 2.  One of the most commonly used group of drugs. A medical doctor has to know the definite clinical pharmacologyof antibiotics, how to select & use them rationally.- Avoid adverse effects on the patient- Avoid emergence of antibiotic resistance- Avoid unnecessary increases in the cost of health care
  • 3.  DefinitionAntibiotics are substances that kill or inhibit the growthof micro-organisms. BacteriostaticBactericidal
  • 4. Based on their mechanism ofaction, antibiotics can be dividedinto the following classes: Inhibitors of Cell Wall synthesis Inhibitors of Protein synthesis Inhibitors of Nucleic Acid synthesis
  • 5. This class includes: Penicillin Cephalosporin Carbapenems Monobactams Vancomycin Beta lactamase inhibitorsB – lactamantibiotics
  • 6. Category Parenteral Agents Oral AgentsNatural Penicillins Penicillin G Penicillin VAntistaphylococcalpenicillinsNafcillin, oxacillin DicloxacillinAminopenicillins Ampicillin Amoxicillin andAmpicillinAminopenicillin + β-lactamase inhibitorAmpicillin-sulbactam Amoxicillin-clavulanateExtended-spectrumpenicillinPiperacillin, ticaricillin CarbenicillinExtended-spectrumpenicillin + β-lactamaseinhibitorPiperacillin-tazobactam,ticaricillin-clavulanateTHE PENICILLINS
  • 7. Class Examples Routes ofadministrationFirst generation Cephalexin/cefadroxilCefazolinOrali.v.SecondgenerationCefuroximeCefoxitinOral/ i.v.Third generation CefiximeCeftriaxone/cefotaximCeftazidimeOrali.v.i.v.FourthgenerationCefipime i.v.
  • 8.  Adverse Effects Allergic reactions: itch, rash,fever, angioedema, rarelyanaphylactic reaction GI upset and diarrhoea Interstitial nephritis andincreased renal damage incombination withaminoglycosidesPharmacokinetics Bactericidal Safe in pregnancy Dosage needs to bereduced in cases ofimpaired renal function.
  • 9. This class includes:- Macrolides- erythromycin, clarithromycin, azithromycin Lincosamides- clindamycin Aminoglycosides- gentamicin, tobramycin, amikacin,netilmicin,neomycin, streptomycin. Tetracyclines- tetracycline, doxycycline,minocycline Chloramphenicol
  • 10. Pharmacokinetics: Bacteriostatic Dose adjustment in renalfailure is not necessaryAdverse Effects : GI upset Cholestatic jaundice Prolongation of QT interval(erythromycin) Theophylline, oral anticoagulantscannot be administeredsimultaneously
  • 11. PharmacokineticsPharmacokinetics Bectericidal Negligible oral absorption Dose adjustment iscritical in renalimpairmentAdverse Effects Ototoxic (permanent)Avoid concurrent use ofother ototoxics drugs for eg.Lasix , minocycline Nephrotoxic ( reversible):use cautiously with othernephrotoxic drugs
  • 12. PharmacokineticsBacteriostaticBest oral absorption in fastingstate Adverse Effects Contraindicated in renal failure(except doxycycline and minocycline) Nausea, diarrhoea Binds to metallic ions in bones and teeth (tobe avoided in children andin pregnancy) Phototoxic skin reactions
  • 13. This group includesThis group includes :: Sulphonamides: Sulfamethoxazole, sulfadoxine Trimethoprim Quinolones: Ciprofloxacin, levofloxacin, pefloxacin, ofloxacin, norfloxacin,gatifloxacin, moxifloxacin, sparfloxacin RifampicinAzoles: This group includes- Antibacterial- Metronidazole, secnidazole, tinidazole, Antihelminth- Albendazole, Mebendazole, thiabendazole
  • 14. Pharmacokinetics Bactericidal Well absorbed orally withgood bioavailability Dose reduction necessary inrenal failureAdverse Effects Fatal marrow dysplasia andhaemolysis in G6PDdeficiency Skin and mucocutaneousreactions: Stevens- Johnsonsyndrome Contraindicated inpregnancy
  • 15. Pharmacokinetics Bectericidal Well absorbed after oraladministration Dose adjustment requiredin renal impairment(except moxifloxacin and trovafloxacin) These two drugs arecontraindicated in hepaticAdverse Effects GI side effects CNS effects such as restlessness,headache, insomnia, confusion andseizures in the elderly Rare skin reactions Should be avoided in pregnancy Not routinely recommended for use inpatients under 18 yearsof age
  • 16. Pharmacokinetics Almost completelyabsorbed after oraladministration (60% afterrectal administration).Adverse Effects Metallic taste Severe vomiting if taken withalcohol (disulfiram likesyndrome )
  • 17.  CNS: Meningitis, brain abscess etc Respiratory: URTI, Pneumonia, Lung abscess, Bronchiectasis CVS: Acute rheumatic fever, Infective endocarditis GIT and HBS: Cholera, Bacillary dysentery, Enteric fever,gastroenteritis, peritonitis,liver abscess Genitourinary: UTI, pyelonephritis, STDs Skin : Cellulitis necrotizing fascitis Musculoskeletal: Osteomyelitis, Septic arthritis Mycobacterial Infections: Tuberculosis, Leprosy Chlamydial Infections Systemic Infections: Sepsis syndrome
  • 18.  62 year old male presents to your clinic with c/o: Cough withexpectoration x 4days◦ Intermittent fever, measured to 100.8◦ Chest pain – Rt side PMHx◦ Healthyo No H/O hospitalization in recent pasto not on any medication Drink socially , non smoker
  • 19.  ExamVS – temp 100.3, P 92, RR 18, Spo2 - 96% on room air, BP123/75HEENT – normalNeck – normal w/o palpable LN or TMGLungs – Bronchial breath sound in I/S , I/A on Rt side, clear atbases,CV – normalLegs – no edema
  • 20. Case 1
  • 21.  Community –acquired Pneumonia (CAP) Recent onset of- Fever- Productive cough- TLC- CXR Why CAP- Healthy adult with no H/O hospitalization in recent past& was not taking any antibiotics
  • 22. Common Outpatient Bacterial Etiologies
  • 23. AntibioticsAntibiotics Oral macrolide Erythromycin Azithromycin ClarithromycinThis patient’s pneumonia is mildPreviously healthyNo antibiotics in past 3 months
  • 24.  In patients who are older, have comorbid illnessesLevofloxacin Moxifloxacin In patients treated with antibiotics within the last 90 days. Respiratory quinolonesMoxifloxacinLevofloxacinGemifloxacinor B- lactamAmoxicillin + ClavunateCefuroxime
  • 25.  Beta-lactam + macrolideCeftriaxone or cefotaximeErythromycin, azithromycin, or clarithromycinOR Fluoroquinolone with antistreptococcal activityLevofloxacin or moxifloxacin
  • 26. Trimethoprim/sulfamethoxizole x 3 dayswomen with risk factors, complicated UTIFluoroquinolone x 3 days: Ciprofloxacin Norfloxacin OfloxacinNitrofurantoin x 7 days
  • 27.  Initial drug selections:FluoroquinolonesCiprofloxacinLevofloxacinCephalosorinCeftriaxoneCefotaxime+ Amikacin
  • 28.  57 years male painful rash on his right leg. 5 daysago he developed a blister on his foot after wearing anew pair of shoes.c/o fever with chills PMHx – COPD, high cholesterolSocial – stopped tobacco two years ago.
  • 29.  Exam Temp 101.2 otherwise stable , APPP Exam unremarkable except for Lungs – few inspiratory rales Right leg …
  • 30.  Outpatient Treatment: non-MRSAAntistaphylococcal penicillinDicloxacillinFirst-generation cephalosporinCephalexin Inpatient Treatment: non-MRSA Amoxicillin + Clavunate Clindamycin is a good alternate with penicillin allergy Surgical opinion
  • 31.  A 43 year old male presents with 10 days of purulentrhinorrhea, subjective fevers, and facial headaches. PMHx – HTN, high cholesterol Meds – lisinopril/HCTZ FamHx – noncontributory
  • 32. Exam HEENT – VS normal tenderness over right maxillary sinus Exam otherwise unremarkable Diagnosis? Sinusitis
  • 33. Mild Acute Bacterial Sinusitis (ABS)AmoxicillinAmoxicillin/clavulanateCefuroxime axetilCefpodoximeOrantistrep. fluoroquinolones:LevofloxacinMoxifloxacin
  • 34.  Drug option in the case of allergies to penicillinand cephalosporin with Mild ABS:◦ Doxycycline◦ Trimethoprim/sulfamethoxizole◦ Azithromycin◦ Clarithromycin
  • 35.  Drug option in the case of allergies to penicillin andcephalosporin with Moderate to Severe ABS:◦ Antipneumococcal fluoroquinolone: Levofloxacin Moxifloxacin
  • 36. 42 years male with 5 days of progressive diffuseheadache, mildly stiff neck,fever vomiting, confusion.PMHx – none knownPSHx - none
  • 37. Exam VS: T 100.9, Pulse 96, RR 16, BP 138/82 Gen: mildly ill appearing Mental status: orientation to place & person not time HEENT: mild photophobia Neck: mild pain with flexion (kernig sign +ve ) Skin: no rash
  • 38.  Lab.- TLC - 16000 DLC - N80 L18 CECT Head - normal study CSF - TLC – 412DLC – N 96 L4protein – 110mg/dlsuger - 23 mg/dl
  • 39.  Adults(<55years) and children>3 months old: High dose ceftriaxone or cefotaxime+ Vancomycin 1gm IV BD Adults > 55years of age , patient with alcoholismor other debilitating illness High dose ceftriaxone /cefotaxime+ Vancomycin 1gm IV BD+ Ampicillin 2gm/ 4horly2gm IV BD
  • 40. Cholera:Tetracycline 250 mg 6-hourly for 3 days,Doxycycline 300 mg single dose or Ciprofloxacin 1g in adultsBacillary Dysentery:Ciprofloxacin 500 mg 12-hourly for 3 daysHelicobacter pylori Infection:Two antibiotics (from amoxicillin, clarithromycinand metronidazole) for 7 days
  • 41. Aetiology: Salmonella typhi and Salmonella paratyphi A and BCiprofloxacin 500 mg 12-hourlyOfloxacin 400 mg every 12 hourlyCeftriaxone 2gm IV BDAzithromycin 1gm once daily x 5 daysTreatment should be continued for minimum 10 days.Or5 days after resolution of fever
  • 42.  Aetiology (pyogenic): E.coli, various streptococci(amoebic): Entamoeba histolytica Management:o Pyogenic: Combination of antibiotics e.g3rd gencephalosporin, gentamicin and metronidazoleo Amoebic: Metronidazole (800 mg 8-hourly for 10 days)or tinidazole (2 g daily for 3 days)Luminal amoebicide-diloxanide furoate (500 mg 8-hourly for 10 days)
  • 43. Gastro-Intestinal:Ancylostoma, Ascaris:Albendazole 400 mg single dose or Mebendazole 100mg 12 hourly for 3 daysTissue parasite:Filariasis: Caused by Wuchereria bancrofti Treatment: Diethylcarbamazine 6 mg/kg body wt.orally in 3 divided doses for 12 days.
  • 44.  Avoid tetracycline Staining of teeth and bones in babies Acute yellow atrophy of lever , pancreatitis in mother Avoid sulfa drugs in the third trimester May be associated with kernicterus Avoid aminoglycosides Kidney toxicities Can cause foetal ear damage FluoroquinolonesConcerns about cartilage development
  • 45.  Treat the Mother first and the baby will appreciate it  Penicillins and cephalosporins are generally safe inpregnancy. Macrolides are generally safe- They may increase nausea early on
  • 46. Is antibiotic necessaryWhat is the mostappropriate antibioticH/OAllergyPregnancyRenal dysfunctionLiver DiseaseDose/Frequency/Route/DurationMonitor side effects