chapter
Antibiotics – aminoglycosides
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Halve the dose of antibiotic. Uncertain if this applies to adults but suggest check levels. Otherwise use an alternative NSAID

AMINOGLYCOSIDES ANTIBIOTICS

AMINOGLYCOSIDES CEPHALOSPORINS Possible ≠ risk of nephrotoxicity Additive effect; cephalosporins are rarely associated with interstitial nephritis

Renal function should be carefully monitored

AMINOGLYCOSIDES COLISTIN ≠ risk of nephrotoxicity Additive effect Renal function should be carefully monitored

NEOMYCIN PENICILLIN V ↓ levels of phenoxymethylpenicillin and possible therapeutic failure

↓ absorption of phenoxymethylpenicillin due to malabsorption syndrome caused by neomycin

Patients should be monitored for efficacy of phenoxymethylpenicillin

AMINOGLYCOSIDES TEICOPLANIN, VANCOMYCIN

≠ risk of nephrotoxicity and ototoxicity

Additive effect Hearing and renal function should be carefully monitored

AMINOGLYCOSIDES ANTICANCER AND IMMUNOMODULATING DRUGS

AMINOGLYCOSIDES CICLOSPORIN ≠ risk of nephrotoxicity Additive nephrotoxic effects Monitor renal function NEOMYCIN METHOTREXATE – ORAL ↓ plasma concentrations following

oral methotrexate Oral aminoglycosides ↓ absorption of oral methotrexate by 30-50%

Separate doses of each drug by at least 2-4 hours

cisplatin is administered early during the course of aminoglycoside therapy

Additive renal toxicity Monitor renal function prior to and during therapy, and ensure an intake of at least 2 L of fluid daily. Monitor serum potassium and magnesium and correct any deficiencies. Most side-effects of aminoglycosides are dose related, and it is necessary to ≠ interval between doses and ↓ dose of aminoglycoside if there is impaired renal function

AMINOGLYCOSIDES TACROLIMUS Risk of renal toxicity Additive effect Monitor renal function closely

NEOMYCIN ANTICOAGULANTS – ORAL Elevated prothrombin times and ≠ risk of bleeding

The mechanism is not fully understood; however, it is thought that neomycin may ↓ number of vitamin K-producing bacteria in the gastrointestinal tract and/or that the absorption of vitamin K may be ↓ by the neomycin

The INR should be monitored in all patients starting or stopping neomycin therapy. Patients more at risk are those with an inadequate diet

AMINOGLYCOSIDES ANTIDIABETIC DRUGS

AMINOGLYCOSIDES ACARBOSE ≠ postprandial hypoglycaemia and ≠ gastrointestinal effects as a result of the concurrent use of acarbose and neomycin

Neomycin is known to cause ↓ blood glucose levels after meals; when used concomitantly with acarbose, this effect may be ≠. Neomycin also exacerbates the adverse gastrointestinal effects caused by acarbose

Blood glucose levels should be closely monitored; if gastrointestinal signs are severe, the dose of acarbose should be ↓

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DRUGS TO TREAT INFECTIONS ANTIBIOTICS – AMINOGLYCOSIDES

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Mechanism Precautions

metformin

Mechanism uncertain. Metformin does not undergo hepatic metabolism. Renal tubular secretion is the major route of metformin elimination. Aminoglycosides are also principally excreted via the kidney, and nephrotoxicity is an important side-effect

AMINOGLYCOSIDES ANTIFUNGALS – AMPHOTERICIN

Risk of renal failure Additive effect Monitor renal function closely

AMINOGLYCOSIDES ANTIVIRALS

AMINOGLYCOSIDES ADEFOVIR DIPIVOXIL Possible ≠ efficacy and side-effects Competition for renal excretion Monitor renal function weekly AMINOGLYCOSIDES FOSCARNET SODIUM Possible ≠ nephrotoxicity Additive side-effect Monitor renal function closely AMINOGLYCOSIDES NUCLEOSIDE REVERSE

TRANSCRIPTASE INHIBITORS

Possibly ≠ risk of nephrotoxicity Additive effect Avoid co-administration if possible; otherwise monitor renal function weekly

AMINOGLYCOSIDES BISPHOSPHONATES – SODIUM CLODRONATE

Risk of symptomatic hypocalcaemia

Uncertain Monitor calcium levels closely

AMINOGLYCOSIDES CARDIAC GLYCOSIDES – DIGOXIN

1. Gentamicin may ≠ plasma concentrations of digoxin 2. Neomycin may ↓ plasma concentrations of digoxin

1. Uncertain; postulated to be due to impaired renal clearance of digoxin 2. Neomycin ↓ absorption of digoxin; this may be offset in some patients by ↓ breakdown of digoxin by intestinal bacterial

1. Monitor digoxin levels; watch for ≠ levels, particularly in diabetics and in the presence of renal insufficiency 2. Monitor digoxin levels; watch for poor response to digoxin

AMINOGLYCOSIDES DIURETICS – LOOP ≠ risk of ototoxicity and possible deafness as a result of concomitant use of furosemide and gentamicin

Both furosemide and gentamicin are associated with ototoxicity; this risk is ≠ if they are used together

If used concurrently, patients should be monitored for any hearing impairment