Other Antibacterials

While penicillins and cephalosporins dominate the frontlines, there’s a small but mighty group of antibacterials used for very specific roles in pharmacy practice. From chronic UTI prophylaxis to anaerobic infections and Pneumocystis pneumonia, this post breaks down six important agents beyond the usual suspects.

General Principles of Link:

Anti-Infectives

Medicine Link

1. Methenamine Hippurate (Hiprex®, Uramet®)

2. Metronidazole (Flagyl®, Metrogyl®)

3. Nitrofurantoin (Nitrofurantoina – generic)

4. Sodium Fusidate (Fusidic Acid) (Fucidin®)

5. Trimethoprim (Alprim®, Triprima)

6. Co-trimoxazole (Trimethoprim + Sulfamethoxazole)

1. Methenamine Hippurate (Hiprex®, Uramet®)

Class: Urinary antiseptic

Mechanism: Prodrug → forms formaldehyde in acidic urine (pH <5.5) → bactericidal effect

Indication:

• Prophylaxis of chronic or recurrent lower urinary tract infections (UTIs)

Dosing (Adults):

• 1 g orally every 12 hours

Precautions:

• Contraindicated in severe dehydration, renal impairment (CrCl <30 mL/min), gout, and severe liver impairment

• Safe in pregnancy and breastfeeding

Practice Tips:

• Requires acidic urine to work → avoid alkalinisers (e.g., Ural®); consider Vitamin C for acidification

• Not for active infections; refer symptomatic patients

• Monitor adherence, hydration, and urine pH if needed

  
  

2. Metronidazole (Flagyl®, Metrogyl®)

Class: Nitroimidazole antimicrobial

Mechanism: Disrupts DNA synthesis in anaerobic bacteria and protozoa

Indications:

• Anaerobic infections, bacterial vaginosis, Clostridioides difficile, giardiasis, PID, H. pylori, rosacea (topical)

Dosing (Adults):

• General: 200–400 mg orally every 8–12 h

• C. difficile: 400 mg orally every 8 h for 10 days

• Bacterial vaginosis: 400 mg twice daily for 7 days

• Trichomoniasis: 2 g single dose or 400 mg BD × 7 days

Precautions:

• Avoid alcohol (disulfiram-like reaction)

• Dose reduction in severe liver disease

• Safe in pregnancy and breastfeeding (short-course)

Practice Tips:

• CNS effects possible → avoid if seizures

• Take with food to reduce GI upset

• Monitor for neuropathy with prolonged use (>10 days)

• Dark urine is a harmless side effect

  
  

3.Nitrofurantoin (Nitrofurantoina – generic)

Class: Urinary antibacterial

Mechanism: Damages bacterial DNA, protein, and cell walls

Indications:

• Treatment and prevention of lower UTIs

Dosing (Adults):

• Treatment: 50–100 mg every 6 hours × 5 days (women), 7 days (men)

• Prophylaxis: 50–100 mg at night

Precautions:

• Avoid if CrCl <30 mL/min

• Contraindicated in late pregnancy (risk of neonatal haemolysis)

• Avoid long-term use in elderly (risk of lung, liver, nerve toxicity)

Practice Tips:

• Not effective for pyelonephritis or prostatitis

• Monitor LFTs, pulmonary, renal, and neuro status with long-term use

• May cause brown urine (harmless)

  
  

4. Sodium Fusidate (Fusidic Acid) (Fucidin®)

Class: Protein synthesis inhibitor

Indications:

• Systemic: Serious MRSA infections (with rifampicin)

• Topical: Impetigo, infected eczema, minor wounds

Dosing (Adults):

• Oral: 500 mg every 8–12 h

• Topical: Apply 2–3 times daily for up to 10 days

Precautions:

• Stop statins during systemic use (risk of rhabdomyolysis)

• Avoid long-term topical use (resistance)

• Topical form safe in pregnancy/breastfeeding if used on small areas

Practice Tips:

• Not for systemic monotherapy

• Monitor liver function if used long-term or in hepatic impairment

  
  

5. Trimethoprim (Alprim®, Triprima)

Class: Folate synthesis inhibitor (bacteriostatic)

Indications:

• UTIs, prostatitis, epididymo-orchitis, UTI prophylaxis, PJP (with dapsone)

Dosing (Adults):

• Acute UTI: 300 mg at night for 3–7 days

• Prophylaxis: 150 mg at night

• Prostatitis: 300 mg at night for 2–4 weeks

Precautions:

• Monitor potassium (hyperkalaemia risk with ACE inhibitors, elderly)

• Avoid in severe renal impairment (CrCl <10)

• Contraindicated in early pregnancy

Practice Tips:

• Monitor CBC and folate with prolonged use

• Watch for signs of allergic reactions and hyperkalaemia

• Night-time dosing optimises urinary concentration

  
  

6. Co-trimoxazole (Trimethoprim + Sulfamethoxazole)

Brands: Bactrim®, Resprim®, Septrin®

Ratio: 1:5 (160 mg trimethoprim + 800 mg sulfamethoxazole = DS tablet)

Indications:

• Pneumocystis pneumonia (PJP), MRSA skin infections, melioidosis, toxoplasmosis, pertussis

Dosing (Adults):

• Mild infections: 160/800 mg every 12 h

• PJP: 5/25 mg/kg every 6–8 h for 21 days

• Melioidosis: 320/1600 mg every 12 h

Precautions:

• Avoid in sulfa allergy, megaloblastic anaemia, severe renal/hepatic impairment

• Risk of severe skin reactions, blood dyscrasias

• Avoid in pregnancy (especially 1st and 3rd trimesters)

Practice Tips:

• Ensure 2–3 L daily fluid intake to avoid crystalluria

• Monitor CBC, potassium, renal function during therapy

• Watch for signs of rash, fever, cough, sore mouth → may indicate hypersensitivity

  
  

Thoughts for Intern Pharmacists

These “other antibacterials” are often reserved for niche or resistant infections, but they can be practice-defining in the right context. As an intern or early-career pharmacist, keep these tips in your clinical toolkit:

• Know the red flags: renal impairment, sulfa allergy, lupus, G6PD deficiency

• Monitor closely during prolonged or high-dose courses

• Be ready to counsel confidently on side effects, dosing timing, and key interactions