Pathology Handbook

Gentamicin Assay

Synonyms

Gentamicin/Gent Level

Test Includes

Measurement of pre-dose or random levels Gentamicin in the patients serum.

Clinical Indications

OD - All adult patients on once daily Gentamicin should have a trough level taken before the second dose, this should be taken 2 hours prior to the second dose. Levels should be measured every third day if the first level is satisfactory.

BD - Twice or three times daily Gentamicin is only used for a few specific indications, most commonly endocarditis. Adult patients on this regime should have trough and peak levels measured either side of the third or fourth doses. The trough is taken just before the dose and the peak one hour after. Levels should be measured twice weekly if the first level is satisfactory.

Renal patients on CAPD - Levels should be measured twice weekly if the first level is satisfactory.

Children except neonates - Avoid long term Gentamicin in both children and neonates: Maximum course = 7days. Patients should be on once daily Gentamicin. They should have a trough level taken before the second dose-this should be taken 2 hours prior to the dose. Levels should be measured before the fourth dose is satisfactory.

Babies on SCBU - On once daily Gentamicin should have a trough level taken before the second dose - this should be taken 2 hours prior to the dose. Levels should be measured twice weekly if the first level is satisfactory.

Request Form

ICE request.

Availability

On request

Specific Criteria

Clotted blood should be collected.

OD regime - 20-22 hours after the first dose.

BD regime -a) Trough level immediately prior to the drug being given.

b) Peak level 1 hour after dose. It is acceptable/preferable tosend pre and post dose samples with one request form, but thesamples MUST be clearly labelled as pre or post dose and withthe time of collection.

Turnaround Time

All tests will be performed on the same day.

Specimen

Serum.

Volume

5 ml (adult)

Container 

Red or gold top, Lithium Heparin samples (green top) are also acceptable.

Vacutainer gold top

Vacutainer red top

Vacutainer green top

Collection

Samples should be transported to the laboratory as soon as possible.

Causes For Rejection

Unlabbelled/inadequately labelled samples.