What is narrow therapeutic?
Narrow Therapeutic:A narrow therapeutic index (NTI), also called a narrow therapeutic window, means a drug’s effective dose is a similar dose to the dose that could elicit adverse or toxic effects of the drug. Because the margin of safety between the doses causing therapeutic and toxic effects is small, the drug generally needs to be continuously dosed to maintain the desired concentration.
Many medications have narrow therapeutic indices, and thus can cause harm if dosed incorrectly or without medical supervision.
- Drugs with a Narrow Therapeutic Index
- Anticoagulants (e.g. warfarin)
- Anticonvulsants (e.g. phenytoin)
- Anti-arrhythmics (e.g. digoxin)
- Some chemotherapeutics (e.g. methotrexate)
- Lithium
- Theophylline
- Tacrolimus
- Cyclosporine
- Considerations for Narrow Therapeutic Index (NTI) Medications:
- Therapeutic Drug Monitoring (TDM): TDM involves routine measurement of the drug concentration in the patient's blood, allowing for adjustment of the drug dose to achieve the desired therapeutic effects while avoiding toxicity.
- Dosing Adjustments: Due to individual variations in drug metabolism, careful dosing adjustments may be required based on factors like age, weight, and concurrent medical conditions.
- Patient Education: Thorough patient education is crucial to ensure proper medication use and adherence. Patients should be well-informed about the potential risks, benefits, and signs/symptoms of toxicity associated with the drug.
- Regular Monitoring: Close clinical monitoring is essential to assess the patient's response to the medication and to detect potential adverse effects early on.
- Multidisciplinary Care: Collaboration between healthcare professionals (e.g. pharmacists, nurses, physicians) is crucial in managing medications with a narrow therapeutic range.