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Sore throat - acute - Management
What are the general issues when prescribing erythromycin?

  • Erythromycin may cause gastrointestinal adverse effects (e.g. nausea, vomiting, diarrhoea) [BNF 54, 2007].
  • Drug interactions:
    • Contraceptives: antibiotics may cause combined hormonal contraceptives (see the pill or the patch in the CKS topic on Contraception) to fail during the first 3 weeks of antibiotic treatment [FFPRHC, 2004; FFPRHC, 2005; FFPRHC, 2007].
      • Advise the woman to use an additional method of contraception during the course of antibiotic treatment and for 7 days afterwards. If this 7-day period runs beyond the end of the pack of contraceptive pills or patch, advise the woman to start a new pack without a break (omitting any inactive tablets).
    • Drugs metabolized by cytochrome P450 isoenzymes (e.g. theophylline, carbamazepine, digoxin, warfarin) [Aronson, 2006]:
      • The effects of these drugs may be increased because erythromycin can inhibit cytochrome P450 isoenzymes.
      • Warfarin: experience in anticoagulant clinics suggests that the International Normalized Ratio (INR) may possibly be altered when warfarin is given with erythromycin [BNF 54, 2007]. Warn the individual of the possible risk of increased bruising and bleeding. Advise when to seek medical help.
    • People taking drugs that can prolong the QT interval (e.g. antiarrhythmics, antipsychotics, tricyclic antidepressants), and people with hypokalaemia:
      • Macrolides also prolong the QT interval, and therefore should, if possible, not be used together with these drugs.
      • Macrolides should not be used in people with hypokalaemia, which also increases the risk of QT prolongation.
    • People taking statins:
      • The risk of myopathy and rhabdomyolysis is increased, as macrolides can inhibit the metabolism of statins [Aronson, 2006].
      • Consider stopping simvastatin for the duration of erythromycin treatment [ABPI Medicines Compendium, 2009].
      • For more information on drug interactions with macrolides, see the British National Formulary [BNF 54, 2007].

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