Natural Penicillin

Question 0

Now the organism used to produce penicillin are ?

Answer 0

Penicillium chrysogenum

Question 1

Organism where penicillin is derived

Answer 1

Penicillium notatum

Question 2

MOA of penicillin

Answer 2

Bactericidal

Inhibit bacterial cell wall synthesis, 3rd stage

Question 3

4 important steps in MOA of penicillin ?

Answer 3

1. Bind to PBP
2. Inhibit transpeptidase (helps in cross linkage)
3. No peptidoglycan produced
4. Autolysin ( supposedly remodel cell wall) will now act and kill the bacteria

Question 4

Mechanism of bacterial resistance in penicillin?

Answer 4

Production of Beta lactamases
Altered PBP - decreased entry of drug into organism
Transpepetidase alteration

Question 5

Pharmacokinetics of Penicillin?

• absrptn in git
• blood ( plasma protein)
• distribution in tissues
• metabolism
• excretion

Answer 5

Poor absptn by oral ( gastric acidity)
All natural penicillin only by parenteral route. IV suitable. IM painful. X displace albumin. Widely distributed. Enters CSF only when meningits. Placentae ok. Metabolised in liver. Active tubular secretion.

Question 6

How to prolong DOA of penicillin?

Answer 6

Probenecid or benzathine added.

Poorly water soluble compounds.

Question 7

Preparations of natural penicillin ?

Answer 7

✅Penicillin G ( benzyl penicillin) 
✅Procaine Penicillin G
✅Fortified Procaine Penicillin G 
( 0.3 MU procaine penicillin G + 0.1 MU penicillin G )
✅Benzathine Penicillin G

Question 8

Antibacterial spectrum of Penicillin

Answer 8

Cocci- gram positive & negative
Bacilli- gram positve
Spirochetes

Question 10

PENICILLIN G
Duration of Action
Dosage
Uses

Answer 10

PENICILLIN G
4~6 hours
0.2~2MU/every 4~12 H IM/IV
▶ Confirmed case of Meningococcal meningitis
▶ Enterococcal endocarditis ( with IV gentamicin, for 6 weeks)
▶ Sensitive pneumococcal organism - 20~24MU/day for 7-10days
▶Anthrax - 8~10 days
▶ Gas gangrene -1~2weeks
▶ Leptospirosis -7 days
▶Neurosyphilis
▶Rat bite fever

Question 11

PROCAINE PENICILLIN G
Duration of Action
Dosage
Uses

Answer 11

PROCAINE PENICILLIN G 
6~12hours 
0.6~1.2MU/every 12 H      IV/IM
▶ Streptococcal pharyngitis, sinusitis, rheumatic fever, otitis media - 10 days 
▶Carrier of C. Diphtheria - 10 days 
▶ Early syphilis & latent syphilis

Question 12

FORTIFIED PROCAINE PENICILLIN G
Duration of Action
Dosage
Uses

Answer 12

FORTIFIED PROCAINE PENICILLIN G 
12~24 hours 
2MU/day 
▶ Sensitive Gonococcal infections 
-14 days 
▶Actinomycosis (+sulphadiazine) for 6 weeks

Question 13

BENZATHINE PENICILLIN G
Duration of Action
Dosage
Uses

Answer 13

BENZATHINE PENICILLIN G 
1~3 weeks 
0.6~2.4MU/month 
▶Streptococcal pharyngitis, sinusitis, otitis media - single dose 
▶All stages of syphilis 
▶Prophylaxis of rheumatic fever

Question 14

Syphilis stages and how penicllin helps

Answer 14

1⃣ Early & latent syphilis
Procaine penicillin
Benzathine penicillin

2⃣ Late syphilis
Benzathine penicillin

3⃣Neurosyphilis/cardiosyphilis
Penicillin G
Benzathine penicillin

Question 15

Limitations of penicillin G

Answer 15

Acid labile
Short DOA
Susceptible to penicillinase enzymes
Narrow antibac specturm

Question 16

Adverse effects of penicillin

Answer 16

Hypersensitivity type 1
Serum sickness
Fever
Severe hypotension, bronchospasm, laryngeal edema
Jarisch Herzheimer reaction in patient with syphilis

Question 17

Treatment of anaphylactic shock

Answer 17

Adrenaline
#⃣0.3~0.4ml of 1:1000 solution IM 

Hydrocortisone 
#⃣ 200 mg IV

Diphenhydramine 
#⃣ 50-100 mg IM or IV

Question 18

Precautions before administration of penicillin

Answer 18

H/o allergy to penicillin
H/o atopy
Sensitivity test , ID 0.02ml penicilllin G

Question 19

How does probenicid act?

Answer 19

Probenecid competes with Blactams for active tubular secretions and retards their excretion. Hence Blactams will not be excreted and plasma conc will increase with DOA.