Examples of drugs suitable for therapeutic drug monitoring include (see footnote
4) the following:^7
- digoxin (target range: 0.8–2μg/L),
- lithium (target range-acute mania: 0.8–1.2 mmol/L, maintenance:
0.4–1.0 mmol/L), - phenytoin (target range: 10–20 mg/L),
- cyclosporine [target range: 50–125μg/L (serum or plasma), 150–400μg/L
(whole blood), concentrations differ for various clinical settings], - tacrolimus [target range: 5–20μg/L (whole blood)],
- sirolimus [target range: 5–15μg/L (whole blood)].
Although TDM services have usually been set up within large hospitals, the
principles of TDM best practice could be applied to the community setting and
should be increasingly easy to incorporate as a result of the continual improvement
of information technology in general practice.^8
Only a limited number of articles have been published that demonstrate the cost-
effectiveness of therapeutic drug monitoring, and there continues to be a debate as
to whether these services make a cost-effective contribution to patient care.^9 ,^10 It
surely cannot be seen as cost-effective if it is used as an unthinking routine in
patients rather than as an aid in resolving clinical problems. TDM has to be applied
rationally, starting from a valid indication to blood sampling and ending with a
sound dosage adaptation decision.
Due to the upswing in individualization of drug therapy and thereby in TDM,
which is foundational to the concept of personalized medicine, the need for
improvement in current deficiencies in the provision of TDM services became
evident. This includes assay selection, laboratory variability in reporting, accessi-
bility, validity of suggested target ranges, and both quality and quantity of
postanalytical advice. Continuing work in ensuring the best practice guidelines
and professional standards of practice in TDM are needed, supported by an active
program of professional development.^11
(^7) Ghiculescu ( 2008 ).
(^8) Gross ( 2001 ).
(^9) Eadie ( 1995 ).
(^10) Eadie ( 1997 ).
(^11) Norris et al. ( 2010 ).
268 D. Vitezic ́et al.