ANarrow Therapeutic Index (NTI) drugis a medication in whichsmall differences in dose or blood concentrationcan lead to serioustoxicityorsubtherapeutic effects. These drugs requirecareful dosing and monitoringto avoid adverse effects or treatment failure.
* Small Margin of Safety:The difference between theminimum effective concentration (MEC)and the minimum toxic concentration (MTC)is very narrow.
* Requires Therapeutic Drug Monitoring (TDM):Blood levels of the drug must be regularly monitored to maintain efficacy while avoiding toxicity.
* High Risk of Adverse Effects:Even minor dosage adjustments or variations in patient metabolism can cause toxicity.
* Strict Pharmacokinetic and Pharmacodynamic Considerations:Factors likerenal and hepatic function, drug interactions, and patient weightsignificantly impact the drug's effect.
* Warfarin (Coumadin) # Risk of bleeding.
* Digoxin # Risk of toxicity affecting the heart.
* Phenytoin # Risk of severe neurological effects.
* Levothyroxine # Risk of under- or over-treatment of thyroid disorders.
* Theophylline # Risk of respiratory or cardiac toxicity.
* Carbamazepine # Risk of serious neurological side effects.
* A. Shorter window of guaranteed stability.# Incorrect. NTI drugs do not necessarily have a shorter shelf-life or stability concerns compared to other drugs. Stability depends on formulation and storage conditions.
* B. Incompatibility with therapeutic monitoring.# Incorrect. NTI drugsrequiretherapeutic monitoring, not the opposite.
* C. Synergistic effect on other medications.# Incorrect. While NTI drugs can interact with other drugs, not all exhibit a synergistic effect (where combined drugs produce a greater effect than expected).
* PTCB PTCE Exam Content Outline - Medication Safety and Quality Assurance(Monitoring NTI drugs).
* FDA Narrow Therapeutic Index Drug List(Guidelines on NTI medications).
* Lexicomp and Micromedex Drug Databases(Provide monitoring recommendations for NTI drugs).
* USP <800> Hazardous Drugs and USP <797> Sterile Compounding Guidelines(Ensure safe handling and dispensing of NTI drugs).
* Mosby's Pharmacy Technician: Principles and Practice(NTI drug classification and monitoring).
Key Characteristics of NTI Drugs:Examples of NTI Drugs:Why the Other Answer Choices Are Incorrect:
Pharmacy Technician References: