Flucloxacillin

See separate guideline for Infective Endocarditis Treatment

Dosing for penicillins should be at the upper end of recommended ranges, particularly for morbidly obese patient with severe infections, considering patient’s renal function.

Renal Impairment

Hepatic impairment

No dose adjustment required.

Use with caution. The risk of flucloxacillin induced liver injury is higher in patients 50 years and over or with severe underlying disease. Hepatic events can be severe and may very rarely result in death. Onset can be delayed by up to two months. Neither route nor dose related.

Flucloxacillin is contra-indicated in patients with a previous history of flucloxacillin associated jaundice/hepatic dysfunction.

Methotrexate: Flucloxacillin can reduce excretion of methotrexate (increased risk of toxicity).

Paracetamol: Risk of high anion gap metabolic acidosis (HAGMA) with concomitant paracetamol. High risk in malnourished states, severe renal impairment, sepsis or if maximum paracetamol doses are used.

Vitamin K antagonists: Appropriate monitoring should be undertaken. It would be prudent to monitor coagulation status within 3 days of starting or stopping a penicillin.

This is not a complete list. Please see the BNF, Summary of Product Characteristics or speak to a pharmacist.

Pregnancy 

Safe, extensive data supporting use of penicillins in pregnancy, though note that no studies have specifically investigated pregnancy outcomes with flucloxacillin.

Breastfeeding 

Very little published evidence: trace amounts in milk, but appropriate to use. Monitor infant for gastro-intestinal disturbances and oral candida infection, especially if used for prolonged periods or in high doses, although these effects are unlikely to occur. There is also a theoretical risk of hypersensitivity.

Flucloxacillin injection contains approximately 51 mg sodium per g. This should be included in the daily allowance of patients on sodium restricted diets.

1. Flucloxacillin Capsules 500 mg [online]. Manufacturer -Flamingo Pharma last updated: 22/2/22 Accessed via: www.emc.medicines.org.uk [Accessed 20/9/23].
2. Flucloxacillin 1000 mg powder for solution for injection or infusion [online]. Manufacturer - Esteve Pharmaceuticals (formerly Intrapharm Laboratories) – last updated: 2023 May 19. Accessed via: www.emc.medicines.org.uk [Accessed 29/8/2023 ].
3. The Renal Drug Database. Flucloxacillin - last updated: 2017 Aug 24. Accessed via: https://renaldrugdatabase.com [Accessed 29/9/2023].
4. Habib G, et al. 2015 ESC guidelines for the management of infective endocarditis: the task force for the management of infective endocarditis of the European Society of Cardiology (ESC) endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM). European heart journal. 2015 Nov 21;36(44):3075-128.
5. UK Medicines Information. How should antibiotics be doses in obesity – last updated 2017 Mar 1. Accessed via: https://www.gloshospitals.nhs.uk/media/documents/Obese_Dosing_2016_update.pdf [Accessed 23/8/2023].
6. Specialist Pharmacy Service – Lactation Safety Information: Flucloxacillin – last updated 2021 Nov 17. Accessed via: https://www.sps.nhs.uk/medicines [Accessed 2023 Aug 29].
7. UK Teratology Information Service - USE OF PENICILLINS IN PREGNANCY– last updated 2019 Jan. Accessed via: https://www.medicinesinpregnancy.org/ [Accessed 2023 Aug 29]