Renal Impairment Summary

Many antibiotics/ Antivirals do not need dose adjustment in mild renal failure. It is important not to under treat infections too.

Several commonly prescribed antibiotics /antivirals do require dose adjustment in moderate to severe renal impairment:
Amoxicillin, Co-amoxiclav, Ciprofloxacin, Clarithromycin, Levofloxacin, Trimethoprim Aciclovir, Valaciclovir. (see table)

If you are prescribing an antibiotic for a patient with chronic renal impairment please refer to the drug SmPC (Health Products Reguatory Authority http://bit.ly/1yLzPiS ) for dose adjust ments in renal impairment.
Another useful reference source is the Renal Drug Handbook®. Elderly patients > 65 years are likely to have some degree of renal impairment.

If you have their serum creatinine, age and weight then you can calculate their creatinine clearance using the formula below or the link to the online calculator below.

Creatinine Clearance:
http://www.mdcalc.com/creatinine-clearance-cockcroft-gault-equation/

Formula: F x (140 – Age) x Weight(kg) / Serum Creatinine (µmol/L) F = 1.23 if male, 1.04 if female

This formula is suitable for use in adults with stable creatinine levels.
If the patient is obese, anuric or in acute kidney failure this formula is not appropriate (NB frail elderly patients with poor fluid intake and an infection – creatinine levels may deteriorate quickly .
NOTE : This formula provides only an estimate of the glomerular filtration rate and may not be accurate in all patients .It may be used as a guide to indicate which patients require dosage adjustment or who should not have medicines but, as it is only an estimate, undue reliance should not be placed on it in calculating doses for patients who appear (on blood biochemistry) to have moderate or severe renal impairment.

If you have known patient with severe renal compromise CKD stage 4 or 5 (eGFR <29ml/min.1.73m2), Creatinine Clearance < 10 ml/min then it is best to seek specialist advice before prescribing antibiotics/ antivirals.

Fosfomycin is contraindicated patients with any degree of renal impairment and is not recommended in patients over 65 years.

Nitrofurantoin: Nitrofurantoin should not be used in patients with severe renal impairment. and is contraindicated at Creatinine clearance less than 60ml/min. Nitrofurantoin is indicated for use in patients with mild to moderate renal impairment but caution should be exercised. Consider checking renal function when choosing to treat with nitrofurantoin, especially in the elderly. If due to multi drug resistance nitrofurantion is the only option then consultant advice should be sought before prescribing.

Macrolides: This class of antibiotics has a number of side effects, interactions and contraindications that should be taken into account when prescribing. Caution should be particularly exercised in patients with cardiac history and the elderly. HPRA website

  Mild renal impairment
CrCl>30ml/min
Moderate renal impairment
CrCl=10-30ml/min
Severe renal impairment
CrCl <10ml/min
Amoxicillin,
Co-amoxiclav
CrCl>30ml/min: Dose as in normal renal function SPC: CrCl=10-30ml/min reduce frequency from tds to bd (i.e. 250/125mg bd, 500/125mg bd) SPC: <10ml/min reduce frequency from bd to od (i.e. 250/125mg od, 500/125mg od)
Cephalexin
(RDH)
Dose as in normal renal function 10-20ml/min: Max 500mg q 8-12h <10ml/min: 250-500mg q 8-12 h
Clindamycin No adjustment required No adjustment required No adjustment required
Ciprofloxacin Dose as in normal renal function SPC: 30-60ml/min: 250-500mg every 12 hours. SPC: <30ml/min: 250-500mg every 24 hours
Clarithromycin RDH: Dose as in normal renal function RDH: 10-20ml/min: 250-500mg bd
SPC: CrCl<30ml/min 250mg od to bd
RDH: CrCl<10ml/min: 250-500mg bd
(vomiting may be a problem at high doses).
SPC: CrCl <30ml/min 250mg od to bd
Doxycycline Dose as in normal renal function Dose as in normal renal function Dose as in normal renal function
Flucloxacillin Dose as in normal renal function Dose as in normal renal function Dose as in normal renal function; maximum 4g daily.
SPC recommends dose reduction or extension of dose interval if CrCl <10ml/min.
Fosfomycin Do not use Do not use Do not use
Metronidazole Dose as in normal renal function Dose as in normal renal function Dose as in normal renal function
Trimethoprim Dose as in normal renal function 100-200 mg 18 hourly 100-200 mg od
Anti-virals
Aciclovir RDH: CrCl: 25-50ml/min: Dose as in normal renal function RDH: 10-25ml/min:
Simplex: 200mg 3 to 4 times a day
Zoster: 800mg every 8 to 12 hours

SPC: 10-25ml/min:
Varicella and Herpes zoster: 800mg every 8 hours

RDH: <10ml/min:
Simplex: 200mg every 12 hours
Zoster: 400-800mg every 12 hours

SPC: <10ml/min:
Varicella and Herpes zoster: 800mg every 12 hours

Valaciclovir
(See SPC for details on Herpes labialis (cold sore) infections)
Herpes simplex: SPC: =30ml/min
Immunocompetent: 500mg bd
Immunocompromised: 1000mg bd.

Herpes zoster: SPC:
30-49ml/min 1000mg bd

Herpes simplex: SPC: <30ml/min: Immunocompetent: 500mg od
Immunocompromised : 1000mg od

Herpes zoster:SPC:
10-29ml/min: 1000mg od

Herpes simplex: SPC: <30ml/min: Immunocompetent: 500mg od
Immunocompromised : 1000mg od

Herpes zoster:
SPC < 10ml/min: 500mg od

(CrCl = Creatinine Clearance. SmPC = Summary of medicinal product characteristics. RDH = Renal Drug Handbook)

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