gentamicin protocol - Hampshire Hospitals NHS Foundation Trust

GENTAMICIN PROTOCOL
A. SINGLE DAILY DOSING
This is recommended in most patients requiring aminoglycoside therapy
Exclusions Seek specialist advice for:
Mod-severe renal failure
(CrCl < 20ml/min)
Endocarditis
Pregnancy and post-partum
Ascites
Major burns
Cystic fibrosis
Prophylaxis
Elderly/frail
NB. Gentamicin should not be given to dehydrated patients due to an increased risk of renal
toxicity
Dosing
• Dose should be 5mg/kg every 24hours (Max initial dose 500mg)
Dose should be based on actual body weight [ABW] unless patient is 20% over ideal body
weight [IBW] in which the Gentamicin Dosing Weight (GDW) should be used – see below
• Gentamicin dosing weight (GDW) = IBW + 0.4 (actual weight – IBW)
e.g. Female patient 103kg and 5ft 4in. IBW = 54.7kg and need to use GDW if > 66kg
GDW = 54.7 + 0.4 (103 – 54.7) = 54.7 + (0.4 x 48.3) = 54.7 + 19.32 = 74kg
Gentamicin dose = 5mg/kg = 5 x 74 = 370mg
Gentamicin comes as 80mg/2ml therefore 360mg is a practical dose
• Give as an IV infusion in 100ml sodium chloride 0.9% or dextrose 5% over 30-60 minutes.
Use GDW if
weight
greater than
WOMEN HEIGHT MEN
IBW (kg)
Feet &
inches
cm
IBW (kg)
Use GDW if
weight
greater than
55 45.5 5.0 152 50.0 61
58 47.8 5.1 155 52.3 63
61 50.1 5.2 157 54.6 66
63 52.4 5.3 160 56.9 69
66 54.7 5.4 163 59.2 72
69 57.0 5.5 165 61.5 74
72 59.3 5.6 168 63.8 77
74 61.6 5.7 170 66.1 80
77 63.9 5.8 173 68.4 83
80 66.2 5.9 175 70.7 85
83 68.5 5.10 178 73.0 88
85 70.8 5.11 180 75.3 91
88 73.1 6.0 183 77.6 94
91 75.4 6.1 185 79.9 96
94 77.7 6.2 188 82.2 99
96 80.0 6.3 191 84.5 102
99 82.3 6.4 193 86.8 105
102 84.6 6.5 196 89.1 107
Produced by the Antimicrobial Management Team 2012. These guidelines are not comprehensive – consult a
Microbiologist if more advice required. For dosing in renal / hepatic failure, seek advice from a pharmacist. Page 1 of 3

Monitoring
1. Arrange for bloods to be taken 6–14 hours after the first dose – this is the prescriber’s
responsibility
2. Take 5-10mls blood in a clotted tube (yellow top)
3. Record the exact sampling time and date of blood sample on request form
4. Record exact time and date of last gentamicin dose administered on request form
5. Use the Urban-Craig nomogram (below) to assess the Gentamicin level and establish the
dosing interval
6. If gentamicin level falls into the q24hr range (appropriate for 24hourly dosing) and renal function
is stable, there is no need to recheck level unless Gentamicin therapy continues beyond 5 days
7. Trough/pre-dose Gentamicin levels (within 2hours of the dose) should be checked twice weekly
if Gentamicin continues beyond 5days and renal function is stable. Trough levels should be
less than 1mg/L before redosing.
8. If the renal function is unstable or the patient requires a dosing interval greater than 24hourly,
discuss frequency of monitoring with a Pharmacist or Microbiologist
9. Monitor serum creatinine at least twice a week or daily if renal function is unstable.
10. Additive toxicity is likely with concomitant nephrotoxic agents e.g. IV Furosemide, Amphotericin
B, Ciclosporin, Cisplatin, Colistin, Methotrexate, radio-contrast media, glycopeptide antibiotics,
Tacrolimus, ACE inhibitors
URBAN-CRAIG NOMOGRAM FOR 5MG/KG GENTAMICIN DOSING ONLY
Produced by the Antimicrobial Management Team 2012. These guidelines are not comprehensive – consult a
Microbiologist if more advice required. For dosing in renal / hepatic failure, seek advice from a pharmacist. Page 2 of 3

Trouble-shooting
• If first level is missed and if renal function is stable and within normal range (i.e. eGFR >
50ml/min and urine output is normal): give 2 nd dose after 24hours and take Gentamicin level 6–
14 hours after 2 nd dose. Seek advice if the level has not been taken after this time.
• If first level is missed and renal function is deranged or urine output has dropped, DO NOT
redose until Gentamicin level < 1mg/L
• If renal function improves during Gentamicin treatment, recheck 6-14hour post-dose level to
ensure dosing interval has not changed
B. MULTIPLE DAILY DOSING
This regimen is recommended for Gram positive Endocarditis
• In these cases, the dose recommended is 1mg/Kg (Ideal Body Weight) 12hourly.
• Give as an intravenous infusion in 100ml glucose 5% or sodium chloride 0.9%, over 30-60
minutes
Monitoring
1. Arrange for bloods to be taken 1hour pre and 1hour post the third dose after start of
therapy or change in dosing – this is the prescriber’s responsibility
2. Take 5-10mls blood in a clotted tube (yellow top)
3. Record the exact sampling time and date of blood sample on request form and medical
notes
4. Record exact time and date of last gentamicin dose administered on request form and
medical notes
5. Pre-dose (trough) levels should be less than 1mg/L
6. Peak (post-dose) levels should be between 3-5mg/L
7. If gentamicin levels fall within range and renal function is stable, recheck pre-dose levels
weekly (levels should be less than 1mg/l).
8. If the renal function is unstable or the patient requires a dosing interval greater than 12hourly,
discuss frequency of monitoring with a Pharmacist or Microbiologist
9. Monitor serum creatinine at least twice a week or daily if renal function is unstable.
10. Additive toxicity is likely with concomitant nephrotoxic agents e.g. IV Furosemide, Amphotericin
B, Ciclosporin, Cisplatin, Colistin, Methotrexate, radio-contrast media, glycopeptide antibiotics,
Tacrolimus, ACE inhibitors
Produced by the Antimicrobial Management Team 2012. These guidelines are not comprehensive – consult a
Microbiologist if more advice required. For dosing in renal / hepatic failure, seek advice from a pharmacist. Page 3 of 3