- Sample: 4mL plain (non-gel) tube preferred or 4mL lithium heparin (non-gel) tube acceptable. Gel containing tubes are NOT acceptable for this assay.
- Sample can be collected ambient (8-24C). After separation, it is stable at 2-8C for up to a week. However, if it is anticipated that the testing would be delayed for more than one week, preferable to store at <= -20C (stable up to 4 weeks). Avoid repeated freeze-thaw cycles. Send the aliquot frozen to Canterbury Health laboratory.
- The suggested sampling strategy is an immediate pre-dose trough collect. For some patients, a two hour post-dose collect is also warranted.
- This test is not available at LabPlus. It will be sent to Canterbury Health laboratories for testing.
Only requests from (or endorsed by) Infectious Disease or Respiratory Medicine specialists will be processed.
Therapeutic drug monitoring of Linezolid is mainly used to assess risk of toxicity especially when it is used in a prolonged manner (exceeding its licenced use of 28 days).
Linezolid is a synthetic antimicrobial of the oxazolidinone class, and is sometimes used as part of a multi-drug regime to treat multidrug-resistant and extensively drug-resistant TB. With its high oral bioavailability and good CNS penetration, it may also have an adjunctive role in the treatment of TB meningitis but evidence is still scanty. On rare occasions, it may also be used in the treatment for some non-tuberculous mycobacterial infections or gram positive pneumonia or skin/soft tissue infections.
Significant adverse drug reactions including peripheral neuropathy, optic neuropathy (relating more to duration of use) and myelosuppression (dose-dependent) have been described.
Lactic acidosis can occur, can be severe, and is more likely in patients with liver and/or renal impairment or circulatory compromise.
Linezolid interacts with Rifampicin and Clarithromycin; the former decreases and the latter increases its plasma concentration. Linezolid is also a reversible, non-selective monoamine oxidase inhibitor, unrelated to its pharmacological anti-microbial use. Special cautions should be made as there can be potentially significant sympathetic or serotonergic interactions when there is concomitant use of medications e.g. sympathomimetics, adrenergic agents, MAOIs, SSRIs, Tricyclic antidepressants or concurrent medical conditions such as uncontrolled hypertension, phaeochromocytoma, thyrotoxicosis or carcinoid syndrome. For details, please refer to Medsafe NZ data sheet.
References:
Martson A-G, Burch G et al. Therapeutic drug monitoring in patients with tuberculosis and concurrent medical problems. Expert opinions on drug metabolism and toxicology 2021; 17(1): 23-39
Zhang Z, Falagas ME et al. Systematic review and meta-analysis of the efficacy and safety of therapy with Linezolid containing regime in the treatment of multidrug-resistant and extensively drug-resistant tuberculosis. J Thorac Ds 2015; 7(4): 603-615
Zyvox - New Zealand data sheet https://www.medsafe.govt.nz/profs/Datasheet/z/Zyvoxinjtabsusp.pdf
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
- Sample: 4mL plain (non-gel) tube preferred or 4mL lithium heparin (non-gel) tube acceptable. Gel containing tubes are NOT acceptable for this assay.
- Sample can be collected ambient (8-24C). After separation, it is stable at 2-8C for up to a week. However, if it is anticipated that the testing would be delayed for more than one week, preferable to store at <= -20C (stable up to 4 weeks). Avoid repeated freeze-thaw cycles. Send the aliquot frozen to Canterbury Health laboratory.
- The suggested sampling strategy is an immediate pre-dose trough collect. For some patients, a two hour post-dose collect is also warranted.