Acute sore throat

• Clarithromycin dosing:

  • In adults: 250 to 500 mg twice daily for 5 days
  • In children aged 1 month to 11 years:
  • Up to 8 kg: 7.5 mg/kg twice daily for 5 days
  • 8-11 kg: 62.5 mg twice daily for 5 days
  • 12-19 kg: 125 mg twice daily for 5 days
  • 20-29 kg: 187.5 mg twice daily for 5 days
  • 30-40 kg: 250 mg twice daily for 5 days
  • In children aged 12-17 years: 250-500 mg twice daily for 5 days
• Erythromycin dosing for pregnant women:

  • 250 mg to 500 mg four times daily or 500 mg to 1,000 mg twice daily for 5 days
• Contraindications and cautions for clarithromycin and erythromycin:

  • Do not prescribe to people at risk of QT prolongation
  • Do not prescribe to people with severe hepatic impairment in combination with renal impairment
  • Prescribe with caution to people with myasthenia gravis, mild to moderate hepatic impairment, coronary artery disease, severe cardiac insufficiency, or bradycardia
  • Adjust dose based on creatinine clearance
• Drug interactions with clarithromycin and erythromycin:

  • Carbamazepine: reduce dose by 30–50%
  • Corticosteroids: monitor for increased levels
  • Lomitapide: contraindicated with erythromycin
  • Rivaroxaban: erythromycin may increase levels
  • Warfarin: monitor INR and adjust dose
  • Statins: increased risk of myopathy
  • Calcium channel blockers: caution advised
  • Drugs that prolong the QT interval: avoid concomitant use
  • Theophylline: monitor levels and adjust dose
• Adverse effects of macrolides:

  • Nausea, vomiting, abdominal discomfort, and diarrhea are common
  • Consider pseudomembranous colitis if severe diarrhea occurs
  • Anaphylaxis, hepatotoxicity, rash, reversible hearing loss, pancreatitis, QT interval prolongation, arrhythmias, Stevens-Johnson syndrome, and toxic epidermal necrolysis are rare adverse effects
• Dosage for adults:

  • 500 mg four times daily, or 1000 mg twice daily (can be increased up to 1000 mg four times daily) for 5 to 10 days
• Dosage for children for phenoxymethylpenicillin:

  • 1-11 months: 62.5 mg 4 times daily, or 125 mg twice daily for 5 to 10 days
  • 1-5 years: 125 mg 4 times daily, or 250 mg twice daily for 5 to 10 days
  • 6-11 years: 250 mg 4 times daily, or 500 mg twice daily for 5 to 10 days
  • 12-17 years: 500 mg 4 times daily, or 1000 mg twice daily for 5 to 10 days
• A 5-day course may be sufficient for symptomatic cure, while a 10-day course may increase the chance of microbiological cure
• Contraindications and cautions:

  • Do not prescribe penicillin to individuals with a history of anaphylaxis, urticaria, or rash immediately after penicillin administration due to the risk of immediate hypersensitivity
  • People with a history of a minor rash or a rash occurring more than 72 hours after penicillin administration are likely not allergic to penicillin and should not have penicillin withheld unnecessarily for serious infections
  • Prescribe penicillins with caution to individuals with a history of atopic allergy or cephalosporin-sensitivity
• Adverse effects of penicillins:

  • Common adverse effects include diarrhoea, fever, hypersensitivity reactions, joint pain, rash, serum sickness-like reaction, and urticaria
  • Rare adverse effects include anaphylaxis, angioedema, cerebral irritation, CNS toxicity, coagulation disorders, encephalopathy, haemolytic anaemia, interstitial nephritis, leucopenia, thrombocytopenia, and neutropenia
• Drug interactions with phenoxymethylpenicillin:

  • Neomycin reduces absorption of phenoxymethylpenicillin
  • Coumarins can alter INR with current penicillin use
  • Methotrexate excretion is reduced by penicillins, leading to increased risk of toxicity
  • Sulfinpyrazone reduces excretion of penicillins
  • Tetracyclines may antagonize the effects of penicillins
  • Oral contraceptives' effectiveness may be impaired by phenoxymethylpenicillin, necessitating additional forms of contraceptives
  • Potassium-sparing diuretics (amiloride or spironolactone) may lead to life-threatening hyperkalaemia