Therapeutic Drug Monitoring Reagents

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Therapeutic Drugs

Therapeutic drugs are used to heal, control, or prevent certain diseases and conditions, and are often required throughout a person’s lifetime to treat chronic conditions.

Most therapeutic drugs have a narrow therapeutic index and require regular monitoring to ensure correct levels of the drug in the blood are maintained. Therapeutic index refers to the difference in the amount that causes a therapeutic effect, and the amount that causes toxicity.

Toxic levels may occur as a result of a person’s ability to absorb the drug i.e. change in health, additional medication that may be reacting with the drug, and, overdose. In addition, sub-therapeutic levels may occur where the patient’s level of the drug is inadequate for their treatment.

  • Liquid-ready-to-use reagents for increased convenience
  • Extensive measuring ranges for ultimate detection of ranges outside the therapeutic range
  • Applications for a wide range of analysers to allow flexibility
  • Multi-analyte controls and calibrators to decrease costs
  • Our TDM controls are lyophilised for enhanced stability
  • Latex-enhanced immunoturbidimetric method and a strong correlation to reference methods.

Therapeutic drugs which may require monitoring include:

  • Carbamazepine, an anti-epileptic drug used in the treatment of seizures; side effects of incorrect dosage can include breathing difficulties, drowsiness and in severe cases seizures, development of lupus and fatal skin reactions
  • Digoxin, a cardiovascular drug used in the treatment of heart conditions such as arrhythmias and heart failure; digoxin toxicity can be associated with health issues such as changes in heart rate and rhythm, gastrointestinal problems and fatigue
  • Phenobarbital, an anti-epileptic drug and sedative-hypnotic drug; incorrect dosage can cause drowsiness, depression, headaches and dizziness with severe cases leading to renal failure, coma and hypotension.
  • Phenytoin, an anti-epileptic drug used to control generalised seizures; incorrect dosage can lead to side effects such as insomnia, nausea, confusion and fatigue, with symptoms of high level toxicity including seizures, unusual bleeding and difficulty breathing or swallowing.
  • Valproic Acid (an anti-epileptic drug); incorrect dosage can result in severe liver impairments, renal function failure and pancreatic function impairments.

Monitoring Dosage is Key

Therapeutic drugs are monitored upon initial dosage to evaluate dosage suitability for the individual, as each person absorbs, metabolises and eliminates drugs at different rates. Depending upon test results, drug dosage may be increased or decreased, and monitored until the blood level reaches the therapeutic range.


Testing may be required in situations where a patient is experiencing side effects to determine if the dose needs to be adjusted; if a patient has experienced a change in health i.e. kidney function, thyroid problems, cancer, or stomach or intestinal issues; if a patient begins taking another medication; if a doctor suspects the patient is not taking the recommended dose of medication; and, if an overdose is suspected.

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