Fosfomycin
General Information
Restricted formulary antimicrobial: For details see OUH netFormulary
Oral: AWaRe antibiotic classification: 'Access'. Use as per guidelines.
IV: AWaRe antibiotic classification: 'Reserve'. All indications to be discussed with Micro/ID.
Elderly patients - Caution is advised when considering the use of IV doses at the higher end of the recommended range (see also recommendations on dosage for patients with impaired renal function below).
Renal and hepatic impairment
Renal impairment
| Creatinine Clearance (ml/min) | Oral Dose | IV dose |
| 41-80 | Dose as in normal renal function |
Dose as in normal renal function Caution should be exercised, particular if doses at higher end of the recommended range |
| 31-40 | Dose as in normal renal function |
Normal loading dose (must not exceed 8g), then 70% of normal daily dose in 2-3 divided doses |
| 21-30 | Dose as in normal renal function |
Normal loading dose (must not exceed 8g), then 60% of normal daily dose in 2-3 divided doses |
| 11-20 | Dose as in normal renal function |
Normal loading dose (must not exceed 8g), then 40% of normal daily dose in 2-3 divided doses |
| Less than 10 | Avoid |
Normal loading dose (must not exceed 8g), then 20% of normal daily dose in 1-2 divided doses |
| HD/HDF/High Flux | Avoid | 2g-4g post-dialysis |
| PD | Avoid |
Normal loading dose (must not exceed 8g), then 20% of normal daily dose in 1-2 divided doses |
Note: dose ranges use creatinine clearance, rather than eGFR.
Hepatic impairment
No dose adjustment required in hepatic impairment.
Pregnancy and breastfeeding
Pregnancy
Discuss with pharmacy.
Breastfeeding
Discuss with pharmacy.
Additional information
IV therapy:
- Monitor electrolytes, particularly sodium and potassium, and fluid balance during therapy. Hypernatremia (each 1g vial for IV administration fosfomycin contains 14mmol of sodium) and hypokalemia requiring potassium supplementation may occur.
- The risk of hypernatraemia and fluid overload should be assessed before starting treatment, especially in patients with a history of congestive heart failure or underlying comorbidities such as nephrotic syndrome, liver cirrhosis, hypertension, hyperaldosteronism, pulmonary oedema or hypoalbuminemia
- Caution is advised in cardiac insufficiency, hypertension, hyperaldosteronism, hypernatraemia or pulmonary oedema.
Fosfomycin oral sachets:
- Food may delay the absorption of fosfomycin. Take on an empty stomach or about 2 – 3 hours after meals.
- Each 3g sachet contains less than 1 mmol sodium (23 mg).
- Patients with fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not use the sachets.
- Concomitant administration of metoclopramide has been shown to lower serum and urinary concentrations of fosfomycin and should be avoided.
- May rarely cause severe hypersensitivity reactions and bronchospasm due to Sulphites.
References
- Summary of Product Characteristics (SPC) for Fomicyt 40 mg/ml powder for solution for infusion. Last updated 31/10/20. Accessed via www.medicines.org.uk on 6/11/21
- Summary of Product Characteristics (SPC) for Monuril 3g granules for oral solution. Last updated 17/5/21. Accessed via www.medicines.org.uk on 6/11/21
- The Renal Drug Database. Fosfomycin. Accessed via renaldrugdatabase.com 19/7/21. Last updated 17/4/18
- BNF online accessed via www.medicinescomplete.com on 6/11/21