This document discusses penicillin antibiotics, including their classification, mechanisms of action, spectra, forms, indications, and adverse effects. It covers natural penicillins, penicillinase resistant penicillins, aminopenicillins, carboxypenicillins, and ureidopenicillins. Key indications for penicillin use include syphilis, gonorrhea, streptococcal infections, and prophylaxis for rheumatic fever. Adverse effects can include rashes, seizures, and bleeding disorders. Aminopenicillins like ampicillin and amoxicillin are also discussed, along with their absorption, interactions, dosing, and common indications for urinary tract infections and respiratory infections.

1. Antibiotics
‘Start smart – then focus’

2. Classification

3. Penicillin
 NATURAL PENICILLIN: benzylpenicillin, phenoxy
methylpenicillin
 PENICILLINASE RESISTANT PENICILLIN:
Methicillin, Cloxacillin, Dicloxacillin
 AMINOPENICILLIN: Ampicillin, Amoxicillin
 CARBOXYPENICILLIN: Carbenicillin
 UREIDOPENCILLIN: Piperacillin

4. Mechanism of action
Competitive inhibition of transpeptidase (penicillin binding protein)
Inhibition of cell wall peptidoglycan synthesis
Bacterial cell swells and burst due to hyperosmotic interior of cell

5. Antibacterial spectrum
Natural penicillin: Treponema pallidum, meningococci, most
streptococci
Penicillinase resistant penicillin: MSSA, streptococci
Aminopenicillins : streptococci, enterococci
Carboxy and ureido penicillins :Pseudomonas aeruginosa,
streptococci, enterococci

6. FORMS
 Pencillin V: oral solution tablets 250mg and 500 mg
 Penicillin G: Injectable 1 million units per 50 ml(aqueous) ;
600,000 units per 1 ml syringe(procaine)

7. INDICATIONS
 Syphilis- Benzathine Penicillin
 Gonorrhea
 Streptococcal infections
 Pneumococcal infections
 Meningococcal infections
 Diphtheria
 Prophylaxis: Rheumatic fever,

8. Syphilis
1. For early syphilis(primary, secondary and early latent syphilis( <2
years): Benzathine penicillin G 2.4megaunits IM single dose
2. For late syphilis(>2 years duration): Benzathine penicillin 2.4
megaunits IM weekly for 3 weeks
3. For neurosyphilis: Aqueous crystalline penicillin G 3-4 megaunits
IV every 4 hourly for 10-14 days

9. Rheumatic fever(RF) prophylaxis
• Benzathine penicillin 1.2 MU IM 3 weekly
or
• Oral penicillin V 250 mg BD

10. Adverse effects
• Rashes
• Allergy
• Seizures
• Encephalopathy
• Leucopenia, thrombocytopenia and coagulation deficiencies

11. AMINOPENCILLIN (Category B)
AMPICILLIN
Food interfere with absorption
Oral absorption incomplete but
adequate
ADR: diarrhea frequent, rashes,
hypersensitivity reaction.
Interferes with deconjugation an
d enterohepatic circulation
Dose: oral 250- 500mg x 6hrly
iv or im 1-2 g x 4/6 hrly
B lactamase inhibitor: salbactum
AMOXICILLIN
Food doesn’t interfere absorption
ADR: same but diarrhea is less
Dose: 500 mgX POX 8hrly
B lactamase inhibitor: clavulonic
acid

13. INDICATIONS
 Urinary tract infections
 Gonorrhea- Ampicillin 3.5g + Probenecid 1g
 Premature rupture of membrane
 Mastitis: dicloxacillin
 Respiratory tract infections
 Meningitis
 Cholecystitis
 Subacute Bacterial Endocarditis- Ampicillin 2g i.v. 6 h
ourly
 H. Pylori
 Septicemia and mixed infections

14. URINARY TRACT INFECTION
Asymptomatic Bacteriuria
3-7 days treatment with
Amoxicillin 500 mg x tds OR
Ampicillin 250 mg x qid OR
Nitrofurantoin 50-100 mg x qid
Pyelonephritis
21 days treatment with above drugs

15. For respiratory tract infections
• Ampicillin: 250mg iv qid
• Amoxicillin: 500mg oral tds for 10- 14 days
For prelabour rupture of membrane
Inj. Ampicillin 1 g IV stat followed by 500 mg IV QID

16. Prophylactic antibiotic for
bacterial endocarditis
• Antibiotic prophylaxis during labor and 48 hours after delivery
is considered appropriate
• Iv ampicillin 2g and gentamicin 1.5 mg/kg(not exceeding 120mg)
• High risk patients are:
1. Structural heart disease
2. Rheumatic heart disease
3. Cyanotic congenital heart disease
4. presense of dental and respiratory tract infection
5. genitourinary procedures and catheterization
6. prosthetic heart valves
7. Prior history of infective endocarditis
8. cardiac transplant