What are the top 15 antibiotics prescribed in general practice, including their doses, indications, contraindications, and preferred usage based on symptoms and patient-specific factors?

Top 15 Antibiotics Prescribed in General Practice: Dosing, Indications, and Clinical Use Guidelines

The most commonly prescribed antibiotics in general practice include amoxicillin-clavulanate, azithromycin, ceftriaxone, ciprofloxacin, and doxycycline, with specific dosages and indications tailored to the type of infection and patient characteristics. 1

1. Amoxicillin-Clavulanate

• Dosage:
  • Adults: 875/125 mg PO twice daily or 500/125 mg PO three times daily
  • Children: 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours
• Indications: Skin and soft tissue infections, respiratory tract infections, otitis media, animal and human bites
• Contraindications: History of penicillin allergy, cholestatic jaundice/hepatic dysfunction with previous use
• When to use: First-line for mixed aerobic-anaerobic infections, particularly when beta-lactamase producing organisms are suspected 1

2. Azithromycin

• Dosage:
  • Adults: 500 mg on day 1, followed by 250 mg once daily for 4 days
  • Children: 10 mg/kg on day 1 (max 500 mg), then 5 mg/kg (max 250 mg) once daily for 4 days
• Indications: Atypical pneumonia, pharyngitis, sinusitis, otitis media, cat scratch disease
• Contraindications: History of cholestatic jaundice/hepatic dysfunction with macrolide use, QT prolongation
• When to use: For respiratory infections with suspected atypical pathogens or in penicillin-allergic patients 1

3. Ceftriaxone

• Dosage:
  • Adults: 1-2 g IV/IM once daily
  • Children: 50-100 mg/kg/day IV/IM divided every 12-24 hours (max 4 g/day)
• Indications: Severe community-acquired pneumonia, meningitis, complicated UTIs, gonorrhea, severe skin infections
• Contraindications: Hypersensitivity to cephalosporins, history of anaphylaxis to penicillins
• When to use: For severe infections requiring parenteral therapy or when oral therapy is not feasible 1

4. Ciprofloxacin

• Dosage:
  • Adults: 500-750 mg PO twice daily or 400 mg IV every 12 hours
  • Children: Generally avoided; if necessary, 10-15 mg/kg every 12 hours (not to exceed 1 g/day)
• Indications: UTIs, prostatitis, gastrointestinal infections, respiratory infections in adults
• Contraindications: Children under 18 (relative), pregnancy, history of tendon disorders
• When to use: For gram-negative infections, particularly in the urinary tract 1

5. Doxycycline

• Dosage:
  • Adults: 100 mg PO twice daily or 100 mg PO once daily
  • Children >8 years: 2-4 mg/kg/day divided twice daily (max 200 mg/day)
• Indications: Respiratory tract infections, skin infections, malaria prophylaxis, acne, STIs
• Contraindications: Pregnancy, children under 8 years
• When to use: For atypical respiratory pathogens, MRSA skin infections, or when macrolides are contraindicated 1

6. Clindamycin

• Dosage:
  • Adults: 300-450 mg PO three times daily or 600 mg IV every 8 hours
  • Children: 10-20 mg/kg/day PO in 3 divided doses or 25-40 mg/kg/day IV in 3 divided doses
• Indications: Anaerobic infections, skin and soft tissue infections, bone and joint infections
• Contraindications: History of C. difficile infection
• When to use: For suspected anaerobic infections or MRSA when other options aren't suitable 2

7. Trimethoprim-Sulfamethoxazole (TMP-SMX)

• Dosage:
  • Adults: 1-2 double-strength tablets (160/800 mg) twice daily
  • Children: 8-12 mg/kg/day (based on TMP component) in 2 divided doses
• Indications: UTIs, MRSA skin infections, Pneumocystis pneumonia
• Contraindications: Pregnancy near term, nursing mothers, infants <2 months, severe renal impairment
• When to use: For community-acquired MRSA infections and uncomplicated UTIs 2

8. Amoxicillin

• Dosage:
  • Adults: 500-875 mg PO three times daily
  • Children: 25-45 mg/kg/day in divided doses every 8-12 hours
• Indications: Streptococcal pharyngitis, otitis media, sinusitis, community-acquired pneumonia
• Contraindications: History of penicillin allergy
• When to use: First-line for susceptible streptococcal infections 3

9. Cephalexin

• Dosage:
  • Adults: 500 mg PO four times daily
  • Children: 25-50 mg/kg/day in 4 divided doses
• Indications: Skin and soft tissue infections, UTIs, streptococcal pharyngitis
• Contraindications: History of anaphylaxis to penicillins or cephalosporins
• When to use: For uncomplicated skin infections caused by susceptible staphylococci and streptococci 2

10. Vancomycin

• Dosage:
  • Adults: 15-20 mg/kg IV every 8-12 hours (30-60 mg/kg/day)
  • Children: 40 mg/kg/day in 4 divided doses
• Indications: MRSA infections, C. difficile colitis (oral form), endocarditis
• Contraindications: Previous hypersensitivity reaction
• When to use: For serious MRSA infections or when beta-lactams are contraindicated 2

11. Metronidazole

• Dosage:
  • Adults: 500 mg PO/IV three times daily
  • Children: 30 mg/kg/day in 3 divided doses
• Indications: Anaerobic infections, C. difficile colitis, bacterial vaginosis, parasitic infections
• Contraindications: First trimester of pregnancy, alcohol consumption during and 48 hours after therapy
• When to use: For anaerobic infections, particularly intra-abdominal and pelvic infections 1

12. Nitrofurantoin

• Dosage:
  • Adults: 100 mg PO twice daily
  • Children: 5-7 mg/kg/day in 4 divided doses
• Indications: Uncomplicated lower UTIs
• Contraindications: Renal impairment (CrCl <30 mL/min), G6PD deficiency, pregnancy at term
• When to use: For uncomplicated cystitis, particularly in areas with high resistance to other antibiotics 1

13. Linezolid

• Dosage:
  • Adults: 600 mg PO/IV twice daily
  • Children: 10 mg/kg every 12 hours
• Indications: MRSA infections, VRE infections, complicated skin infections
• Contraindications: Concurrent MAOI use, uncontrolled hypertension
• When to use: For resistant gram-positive infections when other options have failed 2

14. Moxifloxacin

• Dosage:
  • Adults: 400 mg PO/IV daily
• Indications: Community-acquired pneumonia, complicated skin infections, intra-abdominal infections
• Contraindications: QT prolongation, children under 18 years, pregnancy
• When to use: For respiratory infections requiring broad-spectrum coverage including anaerobes 1

15. Cefazolin

• Dosage:
  • Adults: 1-2 g IV every 8 hours
  • Children: 50 mg/kg/day in 3 divided doses
• Indications: Skin and soft tissue infections, surgical prophylaxis, UTIs
• Contraindications: History of anaphylaxis to penicillins or cephalosporins
• When to use: For surgical prophylaxis and treatment of susceptible gram-positive infections 2

Clinical Decision-Making Algorithm

1. Identify infection site and likely pathogens:

   • Respiratory: Amoxicillin, Azithromycin, Doxycycline
   • Skin/Soft Tissue: Cephalexin, Clindamycin, TMP-SMX
   • Urinary: Nitrofurantoin, Ciprofloxacin, TMP-SMX
   • Gastrointestinal: Ciprofloxacin, Metronidazole

2. Consider patient factors:

   • Age: Avoid tetracyclines in children <8 years
   • Pregnancy: Avoid fluoroquinolones, tetracyclines
   • Renal function: Adjust doses for amoxicillin-clavulanate, ciprofloxacin

3. Assess infection severity:

   • Mild-moderate: Oral therapy (amoxicillin, cephalexin)
   • Severe: Parenteral therapy (ceftriaxone, vancomycin)

4. Consider local resistance patterns:

   • High MRSA prevalence: Consider TMP-SMX, clindamycin
   • High fluoroquinolone resistance: Avoid ciprofloxacin for empiric therapy

Important Caveats and Pitfalls

• Antibiotic resistance: Local resistance patterns should guide empiric therapy; narrow spectrum when culture results are available 1
• Duration of therapy: Most respiratory infections require 5-7 days, skin infections 7-10 days, and UTIs 3-7 days 1
• C. difficile risk: Higher with clindamycin, fluoroquinolones, and cephalosporins; use with caution 1
• Drug interactions: Macrolides and fluoroquinolones have significant drug interactions that must be checked 1
• Pediatric considerations: Avoid tetracyclines in children under 8 years and fluoroquinolones in children under 18 years when possible 1
• Pregnancy considerations: Categorize antibiotics according to safety profile to avoid teratogenicity 1

Remember that antibiotic selection should be guided by the suspected pathogen, site of infection, patient factors, local resistance patterns, and infection severity. Always reassess therapy based on clinical response and culture results when available.