Drug-Drug Interactions and Therapeutic Drug Monitoring Flashcards
Discuss the medical importance of drug-drug interactions in terms of morbidity and mortality.
Drug-drug interactions (DDIs) can significantly impact morbidity (disease and complications) and mortality (death).
Reduced efficacy: DDIs can make medications less effective, leading to treatment failures and worsening health conditions.
Increased toxicity: Interactions can cause harmful drug levels, leading to severe side effects, organ damage, or even death (e.g., bleeding from warfarin interactions).
Adverse reactions: DDIs may cause new or worsened side effects, like excessive sedation or respiratory depression, which can be fatal.
Pharmacokinetic alterations: DDIs can affect drug absorption, metabolism, or excretion, leading to inadequate or toxic drug levels.
Vulnerable populations: Elderly patients, those with chronic conditions, or pregnant women are at higher risk due to polypharmacy or altered organ function.
Specific conditions: Certain drug combinations can worsen conditions like hypertension, diabetes, or infections, leading to severe complications.
Discuss factors predisposing a patient to drug interactions and illustrate this with medically relevant examples.
Polypharmacy: Patients taking multiple medications, especially those with chronic conditions, are at higher risk for DDIs (e.g., warfarin and metronidazole causing bleeding).
Age: Older adults, due to polypharmacy and decreased organ function, are more prone to DDIs (e.g., elderly patients on lisinopril and spironolactone may develop hyperkalemia).
Renal and Hepatic Impairment: Impaired liver or kidney function can lead to drug buildup, causing toxicity (e.g., acetaminophen in liver disease or digoxin in kidney disease).
Genetics: Genetic variations in drug-metabolizing enzymes can affect drug metabolism (e.g., slow metabolism of warfarin increases bleeding risk).
Diet and Lifestyle: Foods like grapefruit and habits like smoking or alcohol use can affect drug metabolism (e.g., grapefruit with statins increases drug concentration).
Acute Illnesses: Illnesses such as fever or dehydration can alter drug effectiveness or metabolism.
Drug Mechanisms: Combining drugs with similar effects (e.g., benzodiazepines and opioids) can increase side effects like sedation and respiratory depression.
Discuss the definition and classification of drug - drug interactions.
Mechanism-Based Classification:
Pharmacokinetic: Interactions that affect absorption, metabolism, or excretion of drugs (e.g., warfarin and metronidazole increasing bleeding risk).
Pharmacodynamic: Interactions affecting the drug’s biological effect, either enhancing (additive/synergistic) or reducing (antagonistic) its action (e.g., benzodiazepines with opioids leading to sedation).
Timing-Based Classification:
Delayed: Interactions that develop over time (e.g., warfarin and metronidazole interaction).
Immediate: Rapid interactions occurring shortly after administration (e.g., nitrate and Viagra causing a drop in blood pressure).
Clinical Classification:
Major: Severe interactions with life-threatening outcomes (e.g., warfarin and aspirin causing bleeding).
Moderate: Moderate interactions needing monitoring or dose adjustments (e.g., antacids and antibiotics).
Minor: Interactions unlikely to cause serious harm (e.g., grapefruit juice with statins).
Discuss the importance of therapeutic drug monitoring.
Therapeutic Drug Monitoring (TDM) is crucial for ensuring that drug levels stay within the therapeutic range to maximize effectiveness and minimize toxicity. It is especially important for drugs with a narrow therapeutic index (e.g., digoxin, lithium, warfarin). TDM helps:
Ensure efficacy by maintaining drug concentrations at effective levels.
Prevent toxicity by avoiding concentrations that could cause harm.
Individualize dosing based on patient-specific factors like age, genetics, and organ function.
Adjust for physiological changes (e.g., kidney or liver issues).
Manage drug interactions that may alter drug levels.
Assess patient adherence to treatment.
Detect adverse effects early, before they become serious.
Commonly monitored drugs include antiepileptics, cardiovascular drugs, antibiotics, immunosuppressants, and lithium. Overall, TDM optimizes treatment, reduces risks, and ensures safe, personalized care.
