Treatment of Meningitis

Penicillin G

Class: Penicillin — β-lactam antibiotic Spectrum: Narrow spectrum

Low activity against Gram-negative bacilli

MOA ⭐: Inhibits bacterial cell wall synthesis

Route ⭐: IV or IM only

Destroyed by gastric acidity → cannot be given orally.

Important facts:

Inactivated by β-lactamase

Short acting: 4–6 hours

Adverse effects ⭐:

Hypersensitivity / anaphylaxis

Nausea, vomiting, diarrhea

Nephritis

Neurotoxicity, especially with large doses

🔥 Exam focus: Penicillin G = narrow spectrum + IV/IM + acid sensitive + β-lactamase sensitive.

Amoxicillin

Class: Penicillin — β-lactam antibiotic Spectrum: Broad spectrum

MOA ⭐: Inhibits bacterial cell wall synthesis

Routes:

Oral → acid stable ⭐

IV

IM

Important combination ⭐: Amoxicillin + clavulanic acid

Clavulanic acid acts as a β-lactamase inhibitor in the combination.

Adverse effects of penicillins:

Hypersensitivity / anaphylaxis ⭐

Nausea, vomiting, diarrhea

Nephritis

Neurotoxicity at large doses

🔥 Exam focus: Amoxicillin = broad spectrum + acid stable + can be given orally

Ampicillin

Class: Penicillin — β-lactam antibiotic Spectrum: Broad spectrum

MOA ⭐: Inhibits bacterial cell wall synthesis

Routes: Oral / IV / IM

⭐ Role in meningitis

Ampicillin IV → used when Listeria monocytogenes is suspected.

According to the lecture, it is weak and is combined with vancomycin.

Important combination: Ampicillin + sulbactam

Adverse effects:

Hypersensitivity / anaphylaxis

Nausea, vomiting, diarrhea

Nephritis

Neurotoxicity at high doses

🔥 HIGH-YIELD: Listeria suspected → Ampicillin IV

Ceftriaxone

Class: 3rd-generation cephalosporin Route: IV

⭐ Very important

3rd-generation cephalosporins can cross the blood-brain barrier (BBB) → important for meningitis.

MOA: Inhibits bacterial cell wall synthesis

Spectrum: Broad spectrum; highly effective against Gram-negative bacilli

Elimination ⭐: ➡ Biliary excretion

Role in meningitis:

Used as empirical IV therapy

Also used for chemoprophylaxis in close contacts of meningococcal meningitis

Adverse effects:

Superinfection

Allergy → cross-allergy with penicillin

Painful IM injection

Thrombophlebitis with IV administration

🔥 Exam focus: Ceftriaxone → biliary excretion. 3rd gen → crosses BBB

Ceftazidime

Class: 3rd-generation cephalosporin Route: IV

MOA: Inhibits bacterial cell wall synthesis

Spectrum: Broad spectrum; highly effective against Gram-negative bacilli

Elimination ⭐: ➡ Renal excretion

Adverse effects:

Superinfection

Allergy / cross-allergy with penicillin

Painful IM injection

Thrombophlebitis with IV

Renal toxicity, especially at high doses ⭐

⚠ Important comparison

Ceftriaxone → biliary excretion Ceftazidime → renal excretion

🔥 Exam trap: 3rd-generation cephalosporins such as ceftriaxone/ceftazidime are NOT effective against Listeria monocytogenes according to the lecture

Imipenem

Class: Carbapenem Spectrum: Broad spectrum

MOA ⭐: Inhibits bacterial cell wall synthesis

Main use: ➡ Resistant infections ➡ Polymicrobial infections

Adverse effects:

Nausea

Vomiting

Diarrhea

Skin rash at injection site

Seizures ⭐

🚨 High-yield warning

Risk of seizures especially when: High dose + renal failure

🔥 Exam association: Imipenem → seizures in high doses, particularly with renal failure

Vancomycin

Class: Non-β-lactam cell-wall inhibitor

MOA ⭐: Inhibits bacterial cell wall synthesis

Spectrum: The lecture summary emphasizes broad-spectrum activity mainly against Gram-positive organisms.

Role in meningitis ⭐

IV vancomycin is used if resistant Streptococcus pneumoniae is suspected.

Important adverse effects ⭐⭐⭐:

Thrombophlebitis

Hypotension

🛑Ototoxicity

Nephrotoxicity

Red man syndrome

🚨 Red Man Syndrome

Cause: Rapid injection → histamine release

Features: ➡ Flushing ➡ Hypotension

Prevention: ➡ Inject vancomycin slowly

Important interaction

Ototoxicity and nephrotoxicity are especially important when vancomycin is given with aminoglycosides.

🔥 Exam favorite: Vancomycin + rapid infusion → Red man syndrome. Vancomycin + aminoglycosides → ↑ nephrotoxicity & ototoxicity

Ciprofloxacin

Class: Fluoroquinolone

MOA ⭐: Inhibits bacterial DNA synthesis

Spectrum:

Mainly Gram-negative

Less activity against Gram-positive organisms

Use in this lecture ⭐: ➡ Chemoprophylaxis

For close contacts of patients with meningococcal meningitis, the lecture lists ceftriaxone or ciprofloxacin for prophylaxis.

Meningitis.pdf

Contraindications ⭐⭐⭐

❌ Children <18 years ❌ Pregnancy ❌ Lactation ❌ History of epilepsy/CNS disorders

Adverse effects:

GIT upset

Headache

Dizziness

Insomnia

Abnormal liver function tests

Skin rash

Photosensitivity

Cartilage damage → arthropathy ⭐

Tendon damage → tendinitis ⭐

Enzyme inhibitor

🔥 Exam favorites: Ciprofloxacin → DNA synthesis inhibitor. Ciprofloxacin → arthropathy + tendinitis. Ciprofloxacin → chemoprophylaxis

⭐ Key association

Penicillin G

Narrow spectrum; IV/IM; acid sensitive

Amoxicillin

Broad spectrum; acid stable/oral

Ampicillin

Listeria

Ceftriaxone

3rd gen; crosses BBB; biliary excretion

Ceftazidime

3rd gen; crosses BBB; renal excretion

Imipenem

Resistant/polymicrobial infection; seizures

Vancomycin

Resistant S. pneumoniae; Red man syndrome

Ciprofloxacin

Chemoprophylaxis; DNA inhibition; arthropathy/tendinitis

⭐ One more exam-important point

Empirical bacterial meningitis treatment: 3rd-generation cephalosporin IV → ceftriaxone or ceftazidime. Add vancomycin if resistant S. pneumoniae is suspected. Use ampicillin IV if Listeria monocytogenes is suspected.