1. Dr. Lokesh
Garg
M.B.B.S. M.D.

2.  One of the most commonly used group of drugs.
 A medical doctor has to know the definite clinical pharmacology
of 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.  Definition
Antibiotics are substances that kill or inhibit the growth
of micro-organisms.
 Bacteriostatic
Bactericidal

4. Based on their mechanism of
action, antibiotics can be divided
into 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 inhibitors
B – lactam
antibiotics

6. Category Parenteral Agents Oral Agents
Natural Penicillins Penicillin G Penicillin V
Antistaphylococcal
penicillins
Nafcillin, oxacillin Dicloxacillin
Aminopenicillins Ampicillin Amoxicillin and
Ampicillin
Aminopenicillin + β-
lactamase inhibitor
Ampicillin-sulbactam Amoxicillin-
clavulanate
Extended-spectrum
penicillin
Piperacillin, ticaricillin Carbenicillin
Extended-spectrum
penicillin + β-lactamase
inhibitor
Piperacillin-tazobactam,
ticaricillin-clavulanate
THE PENICILLINS

7. Class Examples Routes of
administration
First generation Cephalexin/cefadroxil
Cefazolin
Oral
i.v.
Second
generation
Cefuroxime
Cefoxitin
Oral/ i.v.
Third generation Cefixime
Ceftriaxone/cefotaxim
Ceftazidime
Oral
i.v.
i.v.
Fourth
generation
Cefipime i.v.

8.  Adverse Effects
 Allergic reactions: itch, rash,
fever, angioedema, rarely
anaphylactic reaction
 GI upset and diarrhoea
 Interstitial nephritis and
increased renal damage in
combination with
aminoglycosides
Pharmacokinetics
 Bactericidal
 Safe in pregnancy
 Dosage needs to be
reduced in cases of
impaired 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 renal
failure is not necessary
Adverse Effects :
 GI upset
 Cholestatic jaundice
 Prolongation of QT interval
(erythromycin)
 Theophylline, oral anticoagulants
cannot be administered
simultaneously

11. PharmacokineticsPharmacokinetics
 Bectericidal
 Negligible oral absorption
 Dose adjustment is
critical in renal
impairment
Adverse Effects
 Ototoxic (permanent)
Avoid concurrent use of
other ototoxics drugs for eg.
Lasix , minocycline
 Nephrotoxic ( reversible):
use cautiously with other
nephrotoxic drugs

12. Pharmacokinetics
Bacteriostatic
Best oral absorption in fasting
state
 Adverse Effects
 Contraindicated in renal failure
(except doxycycline and minocycline)
 Nausea, diarrhoea
 Binds to metallic ions in bones and teeth (to
be avoided in children and
in pregnancy)
 Phototoxic skin reactions

13. This group includesThis group includes ::
 Sulphonamides: Sulfamethoxazole, sulfadoxine
 Trimethoprim
 Quinolones: Ciprofloxacin, levofloxacin, pefloxacin, ofloxacin, norfloxacin,
gatifloxacin, moxifloxacin, sparfloxacin
 Rifampicin
Azoles: This group includes-
 Antibacterial- Metronidazole, secnidazole, tinidazole,
 Antihelminth- Albendazole, Mebendazole, thiabendazole

14. Pharmacokinetics
 Bactericidal
 Well absorbed orally with
good bioavailability
 Dose reduction necessary in
renal failure
Adverse Effects
 Fatal marrow dysplasia and
haemolysis in G6PD
deficiency
 Skin and mucocutaneous
reactions: Stevens- Johnson
syndrome
 Contraindicated in
pregnancy

15. Pharmacokinetics
 Bectericidal
 Well absorbed after oral
administration
 Dose adjustment required
in renal impairment
(except moxifloxacin and trovafloxacin)
 These two drugs are
contraindicated in hepatic
Adverse Effects
 GI side effects
 CNS effects such as restlessness,
headache, insomnia, confusion and
seizures in the elderly
 Rare skin reactions
 Should be avoided in pregnancy
 Not routinely recommended for use in
patients under 18 years
of age

16. Pharmacokinetics
 Almost completely
absorbed after oral
administration (60% after
rectal administration).
Adverse Effects
 Metallic taste
 Severe vomiting if taken with
alcohol (disulfiram like
syndrome )

19.  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

21.  62 year old male presents to your clinic with c/o: Cough with
expectoration x 4days
◦ Intermittent fever, measured to 100.8
◦ Chest pain – Rt side
 PMHx
◦ Healthy
o No H/O hospitalization in recent past
o not on any medication
 Drink socially , non smoker

22.  Exam
VS – temp 100.3, P 92, RR 18, Spo2 - 96% on room air, BP
123/75
HEENT – normal
Neck – normal w/o palpable LN or TMG
Lungs – Bronchial breath sound in I/S , I/A on Rt side, clear at
bases,
CV – normal
Legs – no edema

25. Case 1

26.  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

28. Common Outpatient Bacterial Etiologies

30. AntibioticsAntibiotics
 Oral macrolide
 Erythromycin
 Azithromycin
 Clarithromycin
This patient’s pneumonia is mild
Previously healthy
No antibiotics in past 3 months

31.  In patients who are older, have comorbid illnesses
Levofloxacin Moxifloxacin
 In patients treated with antibiotics within the last 90 days.
 Respiratory quinolones
Moxifloxacin
Levofloxacin
Gemifloxacin
or
 B- lactam
Amoxicillin + Clavunate
Cefuroxime

33.  Beta-lactam + macrolide
Ceftriaxone or cefotaxime
Erythromycin, azithromycin, or clarithromycin
OR
 Fluoroquinolone with antistreptococcal activity
Levofloxacin or moxifloxacin

40. Trimethoprim/sulfamethoxizole x 3 days
women with risk factors, complicated UTI
Fluoroquinolone x 3 days:
 Ciprofloxacin
 Norfloxacin
 Ofloxacin
Nitrofurantoin x 7 days

41.  Initial drug selections:
Fluoroquinolones
Ciprofloxacin
Levofloxacin
Cephalosorin

Ceftriaxone

Cefotaxime
+ Amikacin

42.  57 years male painful rash on his right leg. 5 days
ago he developed a blister on his foot after wearing a
new pair of shoes.
c/o fever with chills
 PMHx – COPD, high cholesterol
Social – stopped tobacco two years ago.

43.  Exam
 Temp 101.2 otherwise stable , APPP
 Exam unremarkable except for
 Lungs – few inspiratory rales
 Right leg …

47.  Outpatient Treatment: non-MRSA
Antistaphylococcal penicillin
Dicloxacillin
First-generation cephalosporin

Cephalexin
 Inpatient Treatment: non-MRSA
 Amoxicillin + Clavunate
 Clindamycin is a good alternate with penicillin allergy
 Surgical opinion

48.  A 43 year old male presents with 10 days of purulent
rhinorrhea, subjective fevers, and facial headaches.
 PMHx – HTN, high cholesterol
 Meds – lisinopril/HCTZ
 FamHx – noncontributory

49. Exam
 HEENT – VS normal tenderness over right maxillary sinus
 Exam otherwise unremarkable
 Diagnosis?
 Sinusitis

51. Mild Acute Bacterial Sinusitis (ABS)
Amoxicillin
Amoxicillin/clavulanate
Cefuroxime axetil
Cefpodoxime
Or
antistrep. fluoroquinolones:
Levofloxacin
Moxifloxacin

52.  Drug option in the case of allergies to penicillin
and cephalosporin with Mild ABS:
◦ Doxycycline
◦ Trimethoprim/sulfamethoxizole
◦ Azithromycin
◦ Clarithromycin

53.  Drug option in the case of allergies to penicillin and
cephalosporin with Moderate to Severe ABS:
◦ Antipneumococcal fluoroquinolone:
 Levofloxacin
 Moxifloxacin

55. 42 years male with 5 days of progressive diffuse
headache, mildly stiff neck,fever vomiting, confusion.
PMHx – none known
PSHx - none

56. 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


57.  Lab.-
 TLC - 16000
 DLC - N80 L18
 CECT Head - normal study
 CSF - TLC – 412
DLC – N 96 L4
protein – 110mg/dl
suger - 23 mg/dl

60.  Adults(<55years) and children>3 months old:
 High dose ceftriaxone or cefotaxime
+
 Vancomycin 1gm IV BD
 Adults > 55years of age , patient with alcoholism
or other debilitating illness
 High dose ceftriaxone /cefotaxime
+ Vancomycin 1gm IV BD
+ Ampicillin 2gm/ 4horly
2gm IV BD

61. Cholera:
Tetracycline 250 mg 6-hourly for 3 days,
Doxycycline 300 mg single dose or Ciprofloxacin 1
g in adults
Bacillary Dysentery:
Ciprofloxacin 500 mg 12-hourly for 3 days
Helicobacter pylori Infection:
Two antibiotics (from amoxicillin, clarithromycin
and metronidazole) for 7 days

62. Aetiology: Salmonella typhi and Salmonella paratyphi A and B
Ciprofloxacin 500 mg 12-hourly
Ofloxacin 400 mg every 12 hourly
Ceftriaxone 2gm IV BD
Azithromycin 1gm once daily x 5 days
Treatment should be continued for minimum 10 days.
Or
5 days after resolution of fever

63.  Aetiology (pyogenic): E.coli, various streptococci
(amoebic): Entamoeba histolytica
 Management:
o Pyogenic: Combination of antibiotics e.g3rd gen
cephalosporin, gentamicin and metronidazole
o 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)

64. Gastro-Intestinal:

Ancylostoma, Ascaris:
Albendazole 400 mg single dose or Mebendazole 100
mg 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.

65.  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

66.  Treat the Mother first and the baby will appreciate it 
 Penicillins and cephalosporins are generally safe in
pregnancy.
 Macrolides are generally safe
- They may increase nausea early on

67. Is antibiotic necessary
What is the most
appropriate antibiotic
H/O
Allergy
Pregnancy
Renal dysfunction
Liver Disease
Dose/Frequency/Route/Duration
Monitor side effects