Clinical use
Therapeutic drug monitoring of amikacin.
Background
Therapeutic drug monitoring is the measurement of specific drug concentrations in the blood at timed intervals, in order to maintain a relatively constant concentration of the medication in the circulation. Monitored drugs tend to have a narrow “therapeutic index” – the difference between the toxic and therapeutic doses of medications. For some drugs, maintaining this steady concentration in the blood cannot be achieved by simply giving a standard dose of medication to everyone. Each person will absorb, metabolise, utilise, and eliminate drugs at different rates based upon their age, general state of health, genetic makeup, and the influence of other medications that they are taking. These factors may change over time and vary from day to day or with various disease states.
Therapeutic drug monitoring (TDM) aims to optimise individual dosage regimens, enabling the assessment of safety and efficacy of certain drugs. Current TDM approaches include measuring drug serum concentration together with appropriate medical interpretation.
Candidate drugs for TDM possess one or more of the following: narrow therapeutic range, high pharmacokinetic (PK) variability and a clear relationship between serum concentration and therapeutic response. TDM is also helpful for the drug optimisation in patients with renal, hepatic or gastrointestinal insufficiency.
Reference ranges
- Once Daily Pre dose <5mg/L
- Post dose 40-45mg/L
- BD or TDS Pre <10mg/L Post 20-30mg/L
Patient preparation
Recommendation from referral lab for sampling: pre dose sample and a post dose sample taken 1h after end of IV/IM admin.
Specimen requirements
Approx. 1-2mLl of separated serum (the minimum acceptable is 100µL) collected in a gold top serum separator tube.
Minimum volume
100µL of serum
Turnaround time
<1 day (at the reference laboratory) if received Monday to Friday between 9am and 3pm.
Analysing laboratory
Antimicrobial Reference Laboratory, Level 2, Phase 1, Pathology Sciences Building, Southmead Hospital, Westbury-on-Trym, Bristol, BS10 5NB
Additional information
Re-assay interval: 6-8 Days – Assuming initial results are within expected range.
Please visit the guidance page for the Antimicrobial Reference Laboratory for more information.