Therapeutic drug monitoring of gentamicin: evaluation of five nomograms for initial dosing at Al-Amiri Hospital in Kuwait.
OBJECTIVE
To compare five published nomograms (Thomson guidelines, Mawer nomogram, rule of eights, Hull-Sarubbi table and Dettli method) for calculating the initial gentamicin dosage regimen in a Kuwaiti population.


METHODS
Based on measured peak and trough gentamicin concentrations, the elimination rate constant and volume of distribution of gentamicin were calculated for each patient (n = 56), using a modified two-point Sawchuk-Zaske method. The calculated individual set of pharmacokinetic parameters and the initial dose regimen recommended by each of the five methods were used to predict the steady-state peak and trough of gentamicin concentrations.


RESULTS
The Thomson guidelines produced consistent results in predicting gentamicin concentrations within the target ranges of peak plus trough, peak only and trough only (63, 75 and 75%, respectively). The Mawer nomogram, Hull-Sarubbi table and Dettli methods achieved similar percentages of patients (46-50%) within the target ranges (5-10 mg x l(-1) for peak and 0.5-2 for trough), whereas empirical dosing and the rule of eights showed the lowest percentages of patients within the peak plus trough target range (25 and 37%, respectively). However, with respect to the underdosing target range (predicted concentration <5 mg x l(-1)), the Thomson guidelines showed that 21% of patients were underdosed.


CONCLUSIONS
The results show that a large number of patients (37-63%) were outside the target ranges in all initial gentamicin dosing methods evaluated in this study. Therefore, serum concentration measurement can be advised to assist in the optimization of gentamicin dose selection.
Al-Lanqawi
Yousef
Y
Department of Pharmacy, Al-Amiri Hospital, Ministry of Health, Kuwait. yousefl@hsc.edu.kw
Capps
Phillip
P
Abdel-hamid
Mohamed
M
Abulmalek
Kefaya
K
Phillips
Dotun
D
Matar
Kamal
K
Sharma
Prem
P
Thusu
Anil
A
D000900:Anti-Bacterial Agents / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001424:Bacterial Infections / Q000188:drug therapy* / Q000378:metabolism; D003404:Creatinine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D005839:Gentamicins / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006801:Humans; D007730:Kuwait; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D012189:Retrospective Studies
D000900:Anti-Bacterial Agents; D005839:Gentamicins; D003404:Creatinine