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Drug Interactions between allopurinol and ampicillin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

ampicillin allopurinol

Applies to: ampicillin and allopurinol

Consumer information for this interaction is not currently available.

MONITOR: Coadministration of allopurinol with ampicillin or amoxicillin may increase the risk of skin rash and hypersensitivity. The mechanism of interaction is unknown, and it is unclear whether the condition of hyperuricemia or the actual exposure to allopurinol is responsible. In a retrospective study, 15 out of 67 patients (22%) who took ampicillin with allopurinol developed a skin rash, compared to 94 out of 1257 patients (7.5%) who took ampicillin without allopurinol. An updated study by the same group of investigators consisted of 252 patients who took ampicillin with allopurinol and 4434 who took ampicillin alone. The incidence of rash was 13.9% in the allopurinol group and 5.7% in the ampicillin-only group. Similar results were reported for amoxicillin. Specifically, 8 out of 36 patients (22%) treated concomitantly with allopurinol developed a rash, compared to 52 out of 887 patients (5.9%) on amoxicillin without allopurinol.

MANAGEMENT: Closer monitoring for the development of skin rash is recommended if ampicillin or amoxicillin are used concurrently with allopurinol. Some authorities suggest using an alternative to ampicillin or amoxicillin in patients receiving allopurinol when possible. Patients should be advised to promptly report any signs of skin hypersensitivity, including rash, pruritus, fever, or chills.

References

  1. Singer JZ, Wallace SL (1986) "The allopurinol hypersensitivity syndrome." Arthritis Rheum, 29, p. 82-7
  2. Boston Collaborative Drug Surveillance Program (1972) "Excess of ampicillin rashes associated with allopurinol or hyperuricemia." N Engl J Med, 286, p. 505-7
  3. (2022) "Product Information. Zyloprim (allopurinol)." Glaxo Wellcome
  4. Jick H, Porter JB (1981) "Potentiation of ampicillin skin reactions by allopurinol or hyperuricemia." J Clin Pharmacol, 21, p. 456-8
  5. (2024) "Product Information. Allopurinol (Sandoz) (allopurinol)." Sandoz Pty Ltd
  6. (2021) "Product Information. Zyloric (allopurinol)." Aspen Pharma Trading Ltd
  7. (2021) "Product Information. Zyloprim (allopurinol)." AA Pharma Inc, 248178
  8. (2024) "Product Information. Allopurinol (allopurinol)." Actavis U.S. (Purepac Pharmaceutical Company)
View all 8 references

Drug and food interactions

Moderate

ampicillin food

Applies to: ampicillin

You may experience reduced absorption of ampicillin in the presence of food. The effectiveness of the antibiotic may be reduced. Ampicillin should be administered one hour before or two hours after meals. This will make it easier for your body to absorb the medication. Penicillin V and amoxicillin are not affected by food and may be given without regard to meals.

Switch to professional interaction data

Moderate

allopurinol food

Applies to: allopurinol

Consumer information for this interaction is not currently available.

ADJUST DOSING INTERVAL: The tolerability of allopurinol may be improved by giving it after a meal. Additionally, when the dose is greater than 300 mg, dividing the total daily dose into smaller doses administered more often may be appropriate to help minimize gastrointestinal irritation.

MONITOR: Concomitant use of allopurinol with central nervous system (CNS) depressants, including alcohol, may potentiate adverse effects such as somnolence and sedation.

MANAGEMENT: To improve tolerability, some manufacturers suggest administering allopurinol after a meal. Additionally, if the daily dose is greater than 300 mg, administering allopurinol in divided doses may help reduce gastrointestinal intolerance. Patients should also be counseled to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them.

References

  1. (2024) "Product Information. Allopurinol (Sandoz) (allopurinol)." Sandoz Pty Ltd
  2. (2021) "Product Information. Zyloric (allopurinol)." Aspen Pharma Trading Ltd
  3. (2021) "Product Information. Zyloprim (allopurinol)." AA Pharma Inc, 248178
  4. (2024) "Product Information. Allopurinol (allopurinol)." Actavis U.S. (Purepac Pharmaceutical Company)
View all 4 references

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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