Can Amoxil (amoxicillin) be taken with allopurinol?

Amoxicillin and Allopurinol Interaction

Amoxicillin can be taken with allopurinol, but there is an increased risk of skin rashes when these medications are used together, so patients should be monitored closely for hypersensitivity reactions. 1

Interaction Details

• The concurrent administration of allopurinol and amoxicillin increases the incidence of rashes compared to patients receiving amoxicillin alone 1
• The exact mechanism of this interaction is not fully understood - it's unclear whether the potentiation of rashes is due to allopurinol itself or the hyperuricemia present in patients taking allopurinol 1
• This interaction is specifically mentioned in the FDA drug label for amoxicillin, indicating its clinical significance 1

Clinical Implications and Monitoring

• Patients should be monitored for signs of hypersensitivity reactions, particularly skin rashes, when taking these medications concurrently 1
• Common manifestations of hypersensitivity may include:
  • Skin reactions (rash, pruritus, urticaria) 1
  • More severe reactions like erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis (rare but serious) 1
• If a rash or other signs of hypersensitivity develop, the risk-benefit of continuing both medications should be reassessed 2

Special Considerations

Renal Function

• Both medications require dose adjustments in renal impairment:
  • Allopurinol dosage should be reduced by 50% or more in patients with renal failure 2
  • Amoxicillin may also require dosage adjustment in patients with significantly impaired renal function 1
• Monitoring renal function is recommended when using either medication, especially in combination 2

Other Important Drug Interactions with Allopurinol

• Allopurinol has significant interactions with other medications that may be more clinically significant than the interaction with amoxicillin:
  • 6-mercaptopurine/azathioprine: Dose reductions of 65-75% are required when used with allopurinol due to risk of severe myelotoxicity 2
  • Warfarin: May require increased warfarin dosing and more frequent INR monitoring 2
  • Cyclosporine: May need dose adjustment 2

Patient Education

• Patients should be advised to report any skin reactions or other signs of hypersensitivity promptly 1
• The benefits of treating both conditions (infection with amoxicillin and hyperuricemia/gout with allopurinol) typically outweigh the risks of the potential interaction 2
• Patients should be reassured that while the risk of rash is increased, most cases are mild and resolve with discontinuation of the medications 1

Bottom Line

While there is an increased risk of rash when amoxicillin and allopurinol are used together, this interaction does not absolutely contraindicate their concurrent use. Careful monitoring for hypersensitivity reactions is warranted, but the clinical benefit of treating both conditions often outweighs the risk of this interaction.