Episode 31
Whispers of Fate
Let’s try yourself!
A. Pulmonary Embolism from Deep Vein Thrombosis (DVT)
B. Acute Respiratory Depression from Opioid and Benzodiazepine Interaction
C. Cardiac Arrest from Drug-Induced QT Prolongation
Choice 1: Pulmonary Embolism from Deep Vein Thrombosis (DVT)
Pharmacology & Pharmacotherapy Analysis
A pulmonary embolism (PE) often results from deep vein thrombosis (DVT), a blood clot that can travel to the lungs and obstruct blood flow, causing sudden respiratory failure. This is particularly common in patients who have been immobile for long periods or who are at elevated risk due to conditions like cancer, recent surgery, or inherited clotting disorders.
Why This Cause is Unlikely
Absence of Clotting Agents or Recent Trauma: The patient’s medical history lacks the necessary risk factors, such as major surgery, trauma, or immobilizing medical conditions.
Lack of Anticoagulant Interaction: The patient wasn’t on anticoagulants or medications that would typically promote clot formation.
No Immediate Link to Medications: Without a history of clot-promoting drugs (e.g., oral contraceptives or hormone replacement), there’s no direct pharmacological trigger.
Practical Mnemonics and NAPLEX Tips
Mnemonic for PE risk factors: "THROMBOSIS"—Trauma, Hormones, Road trips/long flights, Obesity, Malignancy, Blood disorders, Oral contraceptives, Smoking, Immobility, Surgery.
Important for NAPLEX: Understanding contraindications for medications in DVT/PE patients and knowing when anticoagulants like warfarin or direct oral anticoagulants (DOACs) are indicated, especially for high-risk patients.
Choice 2: Acute Respiratory Depression from Opioid and Benzodiazepine Interaction
Pharmacology & Pharmacotherapy Analysis
Combining opioids with benzodiazepines is known to cause severe CNS and respiratory depression, potentially fatal when both drugs potentiate each other's effects on the central nervous system. Opioids depress the medullary respiratory center, while benzodiazepines increase GABAergic inhibition, further reducing respiratory drive.
Why This Cause is Unlikely
Toxicology Report Shows Therapeutic Levels: Toxicology indicates that both the opioid and benzodiazepine were within safe therapeutic levels, making severe respiratory depression less likely.
Respiratory Suppression Signs Absent: The symptoms reported (e.g., sleepiness) weren’t pronounced enough to indicate severe respiratory suppression.
Insufficient Evidence of Overdose: While therapeutic levels were present, there is no evidence that either drug alone or in combination reached a toxic threshold.
NAPLEX Relevance
Opioid-Benzo Combo Mnemonic: “Do Not Cross” — Dangerous when Depressants Narcotics (Opioids) and Central nervous system drugs (Benzos) are Combined Simultaneously.
Important Dose Calculations: Pharmacists need to be proficient in calculating morphine milligram equivalents (MME) and recognizing dose thresholds that increase overdose risk, especially in combinations with other CNS depressants.
Correct Answer: Cardiac Arrest from Drug-Induced QT Prolongation
Pharmacology & Pharmacotherapy Analysis
QT prolongation is a delay in ventricular repolarization, often seen on an ECG, which can lead to arrhythmias like Torsades de Pointes (TdP), a potentially fatal condition if it progresses to ventricular fibrillation. Drug-induced QT prolongation is often linked to medications that inhibit potassium ion channels (specifically, hERG channels).
Mechanism of Drug Interaction: The patient’s combination of an antibiotic (e.g., a macrolide like azithromycin) and an antiarrhythmic (e.g., amiodarone) can inhibit the cardiac potassium channels (hERG), prolonging the QT interval. This combined effect increases the likelihood of arrhythmia.
Elevated Risk: In patients with other risk factors—such as electrolyte imbalances (e.g., hypokalemia, hypomagnesemia), advanced age, or pre-existing heart conditions—the additive effect of QT-prolonging drugs can trigger lethal arrhythmias.
Undetected Risk Factor: The patient’s slight ECG abnormalities and recent prescription increase the probability of TdP, indicating the fatal arrhythmia was drug-induced, a condition that often lacks premonitory symptoms before sudden death.
Practical Mnemonics and NAPLEX Tips
Mnemonic for QT Prolonging Drugs: “ABCDE Drugs Can Kill” — Antiarrhythmics (amiodarone, sotalol), Biotics (macrolides, fluoroquinolones), CNS drugs (antipsychotics), Diuretics, Electrolyte imbalances, with K(potassium) levels needing close monitoring.
Important for NAPLEX: Be familiar with identifying high-risk patients and contraindications in those on QT-prolonging agents. Also, know dose adjustment in patients with renal/hepatic impairment that can elevate drug levels.
Clinical Pharmacy Perspective on Risk Reduction
Patient Assessment: This case emphasizes the importance of reviewing new prescriptions against existing medications to avoid cumulative QT prolongation risks.
Therapeutic Monitoring: A pharmacist’s role is crucial in ensuring that medications with overlapping cardiac effects, like macrolides and antiarrhythmics, are not prescribed simultaneously without close monitoring.
Electrolyte Monitoring: Regular lab work (electrolytes, renal/hepatic function) can help identify patients at increased risk, allowing for preemptive interventions.
Final Decision for the Pharmacist’s Role
Upon reviewing the evidence, the pharmacist, conclude that drug-induced QT prolongation was the likely cause of death due to the additive effects of the patient’s antibiotic and antiarrhythmic prescriptions. This assessment underscores the importance of drug interaction vigilance, particularly for medications affecting the heart's electrical activity.
Mockup Test
1. A patient is prescribed amoxicillin 500 mg every 8 hours. How many grams of amoxicillin will the patient receive in 24 hours?
A) 0.5 g
B) 1.5 g
C) 2.0 g
D) 3.0 g
2. A child weighing 20 kg is prescribed a dose of 10 mg/kg of a medication. What total dose should be administered?
A) 100 mg
B) 150 mg
C) 200 mg
D) 250 mg
3. A medication is available in a concentration of 25 mg/mL. If a patient needs a 75 mg dose, how many mL should be administered?
A) 1 mL
B) 2 mL
C) 3 mL
D) 4 mL
4. A physician orders 1 L of D5W to be infused over 8 hours. The IV set delivers 15 drops/mL. What should the drip rate be in drops per minute?
A) 15 drops/min
B) 25 drops/min
C) 31 drops/min
D) 50 drops/min
5. A patient is prescribed 0.4 mg/kg of a drug. If the patient weighs 70 kg, what dose should be administered?
A) 14 mg
B) 28 mg
C) 35 mg
D) 56 mg
6. An order is written for 500 mg of a drug to be diluted in 250 mL of saline to be infused over 2 hours. What is the infusion rate in mL per hour?
A) 100 mL/hr
B) 125 mL/hr
C) 150 mL/hr
D) 175 mL/hr
7. A patient is receiving a continuous infusion of dopamine at 10 mcg/kg/min. The patient weighs 60 kg. What is the infusion rate in mcg per minute?
A) 300 mcg/min
B) 500 mcg/min
C) 600 mcg/min
D) 700 mcg/min
8. A patient is prescribed a loading dose of 2 mg/kg of a medication. The patient weighs 80 kg. How many mg of the medication should be administered for the loading dose?
A) 100 mg
B) 120 mg
C) 160 mg
D) 200 mg
9. A patient is to receive 1,000 mg of vancomycin in 250 mL to be infused over 2 hours. What is the infusion rate in mL per hour?
A) 100 mL/hr
B) 125 mL/hr
C) 150 mL/hr
D) 175 mL/hr
10. An IV antibiotic is to be given at a dose of 15 mg/kg every 8 hours. If a patient weighs 50 kg, what dose should be given every 8 hours?
A) 500 mg
B) 650 mg
C) 700 mg
D) 750 mg
11. A patient is prescribed 0.2 mg/kg/hr of an IV drug. If the patient weighs 60 kg, what should be the infusion rate in mg per hour?
A) 6 mg/hr
B) 8 mg/hr
C) 10 mg/hr
D) 12 mg/hr
12. A 5 mg/mL solution is ordered for a patient to receive 10 mg. How many mL should be given?
A) 1 mL
B) 2 mL
C) 2.5 mL
D) 3 mL
13. A medication is dosed at 30 mg/m^2. If a patient has a body surface area (BSA) of 1.8 m^2, what dose should be administered?
A) 30 mg
B) 45 mg
C) 54 mg
D) 60 mg
14. A patient requires 0.1 mg/kg of a drug. If the patient weighs 80 kg, how many mg should they receive?
A) 4 mg
B) 6 mg
C) 8 mg
D) 10 mg
15. A 2-year-old child requires a dose of acetaminophen 15 mg/kg. The child weighs 12 kg. What is the correct dose in mg?
A) 100 mg
B) 150 mg
C) 180 mg
D) 200 mg
16. A patient is to receive 2 grams of medication every 12 hours. What is the total daily dose?
A) 2 grams
B) 4 grams
C) 6 grams
D) 8 grams
17. A 1 L IV bag contains 10 grams of a drug. How many mg/mL are in this solution?
A) 1 mg/mL
B) 5 mg/mL
C) 10 mg/mL
D) 20 mg/mL
18. A medication is supplied as 250 mg per 5 mL. If a patient requires a dose of 500 mg, how many mL should be administered?
A) 5 mL
B) 10 mL
C) 15 mL
D) 20 mL
19. A drug is prescribed at 1.5 mg/kg/day in divided doses every 8 hours. If a patient weighs 40 kg, what is the dose for each administration?
A) 15 mg
B) 20 mg
C) 25 mg
D) 30 mg
20. A patient weighing 70 kg requires 0.5 mg/kg of a medication as a one-time dose. How many mg should be administered?
A) 30 mg
B) 35 mg
C) 40 mg
D) 45 mg
Mockup Test Detailed Answers
1. Answer: B) 1.5 g
Explanation: The patient takes 500 mg every 8 hours, which amounts to 1,500 mg in 24 hours (500 mg × 3 doses).
2. Answer: A) 100 mg
Explanation: The total dose is calculated by multiplying the weight (20 kg) by the dose per kg (10 mg), resulting in 200 mg.
3. Answer: B) 3 mL
Explanation: To find the volume needed for 75 mg from a 25 mg/mL solution, divide the dose by the concentration: 75 mg ÷ 25 mg/mL = 3 mL.
4. Answer: C) 125 drops/min
Explanation: Infusing 1 L (1,000 mL) over 8 hours means 125 mL/hour. With a drop factor of 15 drops/mL, the drip rate is 125 mL/hr × 15 drops/mL ÷ 60 min/hr = 31.25 drops/min (rounded to 31).
5. Answer: C) 28 mg
Explanation: Multiply the weight (70 kg) by the dose (0.4 mg/kg): 70 kg × 0.4 mg/kg = 28 mg.
6. Answer: B) 125 mL/hr
Explanation: 500 mg in 250 mL over 2 hours equals a rate of 125 mL/hr (250 mL ÷ 2 hr).
7. Answer: A) 300 mcg/min
Explanation: 10 mcg/kg/min for a 60 kg patient equals 600 mcg/min (60 kg × 10 mcg/kg).
8. Answer: C) 160 mg
Explanation: For a loading dose of 2 mg/kg for an 80 kg patient, calculate 80 kg × 2 mg/kg = 160 mg.
9. Answer: B) 125 mL/hr
Explanation: 1,000 mg in 250 mL over 2 hours equals 125 mL/hr (250 mL ÷ 2 hr.)
10. Answer: C) 750 mg
Explanation: 15 mg/kg every 8 hours for a 50 kg patient results in a dose of 750 mg (15 mg × 50 kg).
11. Answer: A) 6 mg/hr
Explanation: 0.1 mg/kg/hr for a 60 kg patient results in 6 mg/hr (0.1 mg × 60 kg).
12. Answer: B) 2 mL
Explanation: To receive a 10 mg dose from a 5 mg/mL solution, calculate 10 mg ÷ 5 mg/mL = 2 mL.
13. Answer: C) 54 mg
Explanation: The dose is calculated as 30 mg/m^2 × 1.8 m^2 = 54 mg.
14. Answer: C) 8 mg
Explanation: 0.1 mg/kg for an 80 kg patient equals 8 mg (0.1 mg × 80 kg).
15. Answer: B) 180 mg
Explanation: 15 mg/kg for a 12 kg child equals 180 mg (15 mg × 12 kg).
16. Answer: B) 4 grams
Explanation: A dose of 2 grams every 12 hours totals 4 grams in 24 hours (2 g × 2 doses).
17. Answer: C) 10 mg/mL
Explanation: 10 grams in 1 L (1,000 mL) results in a concentration of 10 mg/mL (10,000 mg ÷ 1,000 mL).
18. Answer: B) 10 mL
Explanation: To administer 500 mg from a 250 mg/5 mL solution, calculate 500 mg ÷ 50 mg/mL = 10 mL.
19. Answer: C) 25 mg
Explanation: The total daily dose is 60 mg (1.5 mg × 40 kg), which is divided into three doses every 8 hours, yielding 20 mg per dose.
20. Answer: B) 35 mg
Explanation: The dose is calculated as 0.5 mg/kg × 70 kg = 35 mg.