Antibiotics of UTI

1-Sulfonamides(Sulfadiazine-Sulfamethoxazole-Sulfadoxine)

*from short to long acting

*SAQ

MoA: Inhibit bacterial folic acid synthesis by competitively inhibiting dihydropteroate synthase (bacteriostatic alone).

Spectrum: Broad; effective mainly for Gram-positive and Gram-negative urinary pathogens.

Uses: UTI, genital infections, respiratory infections, otitis media.

Side Effects:

Hypersensitivity (rash, urticaria, cross-reactivity with thiazides & sulfonylurea)

Hemolytic anemia in G6PD deficiency⭐️

Kernicterus in neonates

Contraindications:

Pregnancy & lactation

Infants < 6 weeks

Renal or hepatic failure

G6PD deficiency

⭐️Extra Notes: Often combined with Trimethoprim (Cotrimoxazole) to produce synergistic bactericidal effect

Trimethoprim (part of Cotrimoxazole)

MoA: Inhibits dihydrofolate reductase⭐️, blocking folate synthesis; bacteriostatic alone.

Uses: Combined with Sulfonamides for UTI, respiratory, genital infections.

Side Effects & Notes: Same as Sulfonamides; combination increases efficacy, converts to bactericidal action, and reduces resistance .

Nitrofurantoin

MoA: Bacteria reduce the drug to active metabolites → inhibit ribosomal protein synthesis and damage bacterial DNA (bactericidal).

Spectrum: Mainly E. coli, some other urinary Gram-negative bacteria.

Uses: Lower urinary tract infections (cystitis); not for upper UTI.

Side Effects:

Gastrointestinal upset (take with food)

⭐️Turns urine dark orange-brown

⭐️Hemolytic anemia in G6PD deficiency

Contraindications: G6PD deficiency, neonates, pregnancy

Extra Notes: Concentrated in urine, minimal systemic effect; used only in uncomplicated lower UTIs

Tetracyclines (⭐️Doxycycline)saq

⭐️MoA: Bacteriostatic; binds 30S ribosomal subunit → inhibits protein synthesis.

Spectrum: Gram-positive & Gram-negative bacteria, including Mycoplasma and Chlamydia.

Uses: UTI (especially prostatitis), atypical infections.

Side Effects:

⭐️Permanent brown teeth discoloration & ⭐️bone deformity (teratogenic/childhood)

Photosensitivity

Hepatotoxicity

Contraindications: Pregnancy, breastfeeding, children <10 yrs

Aminoglycosides (Gentamicin)

⭐️MoA: Bactericidal, inhibits protein synthesis.

Spectrum: Gram-negative aerobic organisms.

Uses: Severe UTIs (Pseudomonas/Enterobacter), osteomyelitis, pneumonia, TB (Streptomycin), topical eye infections (Neomycin).

Side Effects:

⭐️Nephrotoxicity (especially in elderly)

⭐️Ototoxicity

Nerve damage

Neuromuscular blockade

Contraindications: Pregnancy (crosses placenta) .

Cephalosporins (3rd Gen – Ceftriaxone)

MoA: Bactericidal; inhibits peptidoglycan synthesis → disrupts bacterial cell wall.

Spectrum: Broad; Gram-negative bacteria (3rd & 4th gen cover meningitis).

Uses: Severe/complicated UTIs, acute prostatitis, respiratory, skin, soft tissue infections, otitis media, Gram-negative meningitis.

Side Effects:

GI: pseudomembranous colitis

Injection site pain & thrombophlebitis

Hypersensitivity: rash, fever, anaphylaxis (cross-reactivity with penicillin)

Extra Notes: Given parenterally .

Fluoroquinolones (Ciprofloxacin)

MoA: Inhibits DNA synthesis (bactericidal).

Spectrum: Broad; includes multidrug-resistant organisms like Pseudomonas.

Uses: UTIs, acute/chronic prostatitis.

Side Effects:

CNS: confusion, insomnia, headache, anxiety

Arthropathy (growing cartilage damage)

Tendonitis

Phototoxicity

Contraindications: <18 yrs, pregnancy, lactation

Extra Notes: Avoid excessive sunlight exposure .