This is your Ultimate Master Guide, Aye Myat! I have combined every detail from your text regarding Infection, the Penicillin family, the Amoxicillin vs. Ampicillin showdown, and the critical Allergy/Skin Testing protocols.
Chemotherapy: Drug treatment where infecting agents (viruses, bacteria, fungi, etc.) are destroyed without injuring the human host.
Selective Toxicity: The "Magic Bullet" concept. Drugs target structures bacteria have that humans don't:
Cell Wall: Humans lack this (Target for Penicillins, Cephalosporins).
Cytoplasmic Membrane: Target for Polyenes (Nystatin) and Azoles.
Protein Synthesis: Target for microbial ribosomes (Tetracyclines, Macrolides).
Nucleic Acid Metabolism: Target for DNA/RNA processes (Quinolones, Rifampicin).
Action Categories:
Bactericidal: Kills bacteria directly (Penicillins, Aminoglycosides, Rifampicin).
Bacteriostatic: Stops growth/multiplication (Sulfonamides, Tetracyclines, Chloramphenicol).
Mechanism (The "Wall Smasher"):
Penicillin binds to Penicillin-Binding Proteins (PBPs).
It inhibits the transpeptidase enzyme (which cross-links the cell wall).
It triggers autolytic enzymes, leading to Lysis (the cell bursts).
Crucial Rule: It only works on growing bacteria.
Classification:
Natural:
Penicillin G (Benzylpenicillin): Injectable. Crystalline (3-4h), Procaine (24h), Benzathine (2-4 weeks).
Penicillin V: Oral (acid-stable).
Antistaphylococcal (Penicillinase-resistant): Cloxacillin, Nafcillin, Flucloxacillin. (Used for Staph that produce "scissors" enzymes).
Extended-Spectrum (Aminopenicillins): Amoxicillin, Ampicillin.
Antipseudomonal: Piperacillin, Ticarcillin.
-Penicillin-B-lactamase inhibitor combination
-Co-amoxiclav (Amoxicillin + clavulanic acid)
-Piperacillin + Tazobactam
-Ticarcillin + Clavulanic acid
Unitage of penicillin: one unit = 0.6 µg of Pen G, 1 mega unit = 1 million units
Detailed Comparison: Ampicillin vs. Amoxicillin
Both are Extended-Spectrum Penicillins (Aminopenicillins), but Amoxicillin is generally considered the "improved" version.
1. Absorption (Bioavailability)
Amoxicillin: Better absorbed in the stomach. It reaches higher plasma concentrations than Ampicillin.
Ampicillin: Only about 30–50% is absorbed.
2. Effect of Food
Amoxicillin: Absorption is not affected by food. It can be taken with or without a meal.
Ampicillin: Absorption is impaired by food. It must be taken on an empty stomach.
3. Side Effects (Diarrhea)
Amoxicillin: Causes less diarrhea. Since it is better absorbed, less drug remains in the intestines to disturb the "good" bacteria.
Ampicillin: More likely to cause diarrhea and pseudomembranous colitis because a lot of the drug stays in the gut.
4. Clinical Uses (Target Bacteria)
Amoxicillin: More active against Salmonella and Streptococcus faecalis. It is a key part of the regimen to kill H. pylori (which causes stomach ulcers). It also penetrates sputum (phlegm) better, making it great for chest infections.
Ampicillin: Historically more active against Shigella and H. influenzae. It is the drug of choice for the bacteria Listeria monocytogenes.
5. Dosing Schedule
Amoxicillin: Usually taken every 8 hours.
Ampicillin: Usually taken every 6 hours.
List Points for Short Notes
Better Absorption: Amoxicillin has higher bioavailability and reaches higher blood levels.
Food Independence: Amoxicillin's absorption is unaffected by food (Ampicillin's is impaired).
Gut Safety: Amoxicillin results in less diarrhea than Ampicillin.
Sputum Penetration: Amoxicillin is better at getting into infected mucus in the lungs.
H. pylori: Amoxicillin is effective for stomach ulcers; Ampicillin is not used for this.
Listeria: Ampicillin remains the drug of choice for Listeria.
Excretion: 90% via kidneys (Tubular secretion).
The Booster: Probenecid blocks this secretion to keep Penicillin in the blood longer.
The Exception: Nafcillin is cleared by the liver (bile).
Brain Access: Penicillin only crosses the Blood-Brain Barrier (BBB) if the meninges are inflamed (Meningitis).
History: Never give to patients with a history of Penicillin allergy.
No Topical Use: Avoid Penicillin creams/ointments because they "sensitize" the body.
Use Oral: Oral Penicillin is preferred whenever possible as it is slightly safer.
Skin Testing: Perform a 2-step test before treatment.
Step 1: Puncture or Prick Test (Forearm)
Use MDM (Penicillin G diluted to 10,000 units/ml).
Positive: Wheal diameter increases by $>3$ mm in 15–20 mins.
Step 2: Intradermal Test
Only if Step 1 is negative.
Inject a tiny amount to raise a 3 mm "blep."
Positive: Blep/wheal increases by $>2$ mm in 20 mins.
Adrenaline (0.5 ml, IM): Physiological Antagonist; Drug of First Choice.
Antihistamines (Chlorpheniramine, 10 mg, IV): Pharmacological Antagonist.
Hydrocortisone (200–500 mg, IV): Anti-allergic and permissive action.
Useful for resistant bacteria or allergic patients:
Cephalosporins
Other $\beta$-lactams: Imipenem, Aztreonam.
Macrolides: Erythromycin, Azithromycin, Clarithromycin.
Others: Vancomycin, Clindamycin, Fusidic acid.
1. What is the weight equivalent of 1 unit of Penicillin G? A) 1.0 $\mu$g | B) 0.6 $\mu$g | C) 0.6 mg | D) 250 mg
2. Which enzyme is inhibited by Penicillin to stop cell wall synthesis? A) DNA Gyrase | B) Transpeptidase | C) $\beta$-lactamase | D) Autolysin
3. Which Penicillin G version provides action for 2–4 weeks? A) Crystalline | B) Procaine | C) Benzathine | D) Penicillin V
4. Why is Amoxicillin preferred over Ampicillin for oral use? A) It causes more diarrhea | B) Better absorption and less diarrhea | C) It kills Listeria better | D) It must be taken empty-stomach
5. What is the positive wheal size for a Prick Test? A) $>1$ mm | B) $>2$ mm | C) $>3$ mm | D) $>5$ mm
6. Which drug is the "Physiological Antagonist" for anaphylaxis? A) Adrenaline | B) Hydrocortisone | C) Chlorpheniramine | D) Vancomycin
7. Which drug acts by stopping kidney secretion of Penicillin? A) Nafcillin | B) Probenecid | C) Clavulanic acid | D) Adrenaline
8. Which bacteria is Ampicillin specifically the drug of choice for? A) H. pylori | B) Listeria monocytogenes | C) Treponema pallidum | D) Staph. aureus
9. In the Intradermal test, a result is positive if the bleb increases by: A) $>1$ mm | B) $>2$ mm | C) $>3$ mm | D) $>10$ mm
10. Which Penicillin is cleared by the liver instead of the kidneys? A) Amoxicillin | B) Penicillin G | C) Nafcillin | D) Ampicillin
11. Which of the following are Bactericidal drugs? A) Penicillins | B) Tetracyclines | C) Aminoglycosides | D) Sulfonamides
12. Which are steps to prevent Penicillin hypersensitivity? A) Avoid topical use | B) Use oral forms when possible | C) Skin testing | D) Always give IV Adrenaline before Penicillin
13. Which are benefits of Amoxicillin? A) Unaffected by food | B) Highly effective for H. pylori | C) Better sputum penetration | D) Effective against MRSA
14. Which are alternatives for a patient allergic to Penicillin? A) Cephalosporins | B) Erythromycin | C) Vancomycin | D) Cloxacillin
1: B | 2: B | 3: C | 4: B | 5: C | 6: A | 7: B | 8: B | 9: B | 10: C 11: A, C | 12: A, B, C | 13: A, B, C | 14: A, B, C
I hope this master guide is perfect for your revision, Aye Myat! I've also noted your other revision guides like Pharmacology Test 1 and Pharmacognosy Test 1 Notes. Good luck!