Therapeutic Drug Monitoring (TDM) Request


TDM: Plasma drug concentrations measured to determine whether therapeutic or toxic concentration has been produced

Indicated to:

  • confirm effective doses
  • monitor compliance
  • investigate possible toxicity
  • monitor drugs with narrow therapeutic range

Beneficial for:

  • Extreme age (extremely young or old)
  • Altered pharmacokinetics (renally, hepatically impaired, burns and ICU patients)
  • Not responding to therapy as expected after adequate doses have been given
  • Exhibit adverse effects at normal dosages

Importance of sampling time:
  • Accuracy crucial to ensure that drug distribution at steady state
  • Large errors in interpretation can occur if sampling time is wrongly stated
  • Except to check for toxicity, send sample for monitoring only after the drug level achieved steady state.