Pharmacology Week 9 Case Study Analyses

Pharmacology Week 9 Case Study Analyses

Scenario 1: Prescription Errors, Classifications, and Mechanisms of Action (MOAs)

Medication	Error	Correct Order	Classification	MOA
Tamsulosin	Incorrect dose (4 mg instead of 0.4 mg)	Tamsulosin 0.4 mg capsule PO once daily, 30 minutes after the same meal; Disp: #30, 2 RF (Ng & Baradhi, 2024)	Alpha-1 blocker	Relaxes smooth muscle in the bladder, neck, and prostate
Levofloxacin	Spelling error  (“levofloxcin”)	Levofloxacin 750 mg PO daily for 5 days; Disp: #5, 0 RF (Podder & Sadiq, 2024).	Fluoroquinolone	Inhibits DNA gyrase and topoisomerase IV (Podder & Sadiq, 2024).
Ciprofloxacin otic	Wrong formulation (otic for eye)	Ciprofloxacin 0.3% ophthalmic solution, 1–2 drops in affected eye Q2H x 2 days, then Q4H x 5 days; Disp: 1 bottle, 0 RF	Fluoroquinolone	Inhibits DNA gyrase and topoisomerase IV (Podder & Sadiq, 2024).
Paxlovid	Reversed dosing label	Paxlovid (nirmatrelvir 300 mg + ritonavir 100 mg) PO BID x 5 days; Disp: 1 dose pack, 0 RF	Antiviral combo	Protease inhibition + boosting agent
Depo-Provera	Incorrect frequency (monthly vs every 3 months)	Depo-Provera 150 mg IM every 3 months; Disp: 1 syringe, 3 RF (Curtis et al., 2024).	Progestin contraceptive	Inhibits ovulation and thickens cervical mucus (Curtis et al., 2024).

Scenario 2: Gonorrhea with Allergies and Empiric STI Coverage

FS is a 26-year-old sexually active female with gonorrhea; she has a known penicillin allergy and latex allergy. In this case, one must select a safe and effective treatment regimen that conforms to the CDC guidelines on the treatment of gonorrhea and the empirical coverage for chlamydia. To prevent reinfection, providing thorough patient education is crucial (CDC, 2021).

Ceftriaxone, a third-generation cephalosporin, is typically first-line. However, in patients with IgE-mediated penicillin allergy, like anaphylaxis or Stevens-Johnson syndrome, cross-reactivity risk exists even when administered in low doses (CDC, 2021). Due to this reason, an alternative treatment is as follows;

Treatment Plan

Gentamicin 240 mg IM once

• Dispense: 1 vial; Refills: 0
• Instructions: Non-latex materials; monitor renal function (Public Health Agency of Canada, 2025)

Azithromycin 2 g PO once

• Dispense: 2 × 1g tablets; Refills: 0
• Instructions: Take with food; watch for GI upset (Public Health Agency of Canada, 2025)

Doxycycline 100 mg PO BID x 7 days is used to empirically treat chlamidia due to its high efficacy especially in the rectal infections.

• Dispense: #14 tablets; Refills: 0
• Instructions: Avoid antacids; wear sunscreen; take on an empty stomach (Mohseni et al., 2023).

Patient Education

It is important to conduct thorough patient education in order to make them part of the solution to their therapeutic journey. The key topics to be discussed with the patient include abstaining from sex for at least seven days post-treatment, testing and treating partners from the past 60 days, and using barrier protection consistently going forward (Springer & Salen, 2023).

Points to Note

• Latex allergy: Ensure non-latex gloves and syringes are used during IM administration.
• Penicillin allergy: Avoid cephalosporins if history suggests an IgE-mediated reaction.
• Dual therapy with gentamicin and azithromycin is effective and safe in this context.
• Doxycycline is preferred for chlamydia due to its higher efficacy, especially for rectal infections.

Scenario 3: Warfarin and Bactrim DS Interaction

JH, a 68-year-old male on warfarin for DVT, was prescribed Bactrim DS for a UTI. His INR is 6.9, which is significantly elevated. One needs to understand the mechanism of this interaction and adjust the patient’s therapy to prevent bleeding risk.

Interaction Mechanism

Bactrim DS (sulfamethoxazole/trimethoprim) interacts with warfarin in multiple ways. Firstly, through CYP2C9 inhibition, Bactrim inhibits the metabolism of S-warfarin, the more potent enantiomer. Another way is through protein binding displacement. Bactrim is highly protein-bound and can displace warfarin from albumin, increasing free drug levels. Lastly, through gut flora disruption, trimethoprim-sulfamethoxazole reduces vitamin K-producing bacteria, enhancing warfarin’s anticoagulant effect (Crader et al., 2023). Clinically, these ways lead to INR elevation can occur rapidly, often within 2–3 days of starting Bactrim; hence, the risk of major bleeding increases significantly when INR > 4.5.

Treatment Adjustments

• Hold warfarin until INR < 3.0.
• Monitor INR every 24–48 hours.
• If bleeding risk increases, give Vitamin K 2.5–5 mg PO once.
• Resume warfarin at reduced dose (for example, 2.5 mg–3.75 mg daily) (Kholmukhamedov et al., 2025).

Medication Orders

• Warfarin 5 mg PO daily – HOLD
• Phytonadione (Vitamin K1) 2.5 mg PO once – if needed (Waheed et al., 2023).

Scenario 4: Vancomycin Dosing & Trough Monitoring

In dosing vancomycin 15 mg/kg IV every 12 hours for a 70 kg patient, using 1 g per 20 mL vials, it is crucial to calculate the dose, volume, and infusion time, assess trough level appropriateness, and explain why vancomycin is usually given IV.

Dose per Administration

• Calculation: 15 mg/kg × 70 kg = 1050 mg per dose
• Rounded: Vancomycin doses are typically rounded to the nearest 250 mg → 1000 mg per dose
• Stock concentration: 1 g (1000 mg) per 20 mL
• Infusion Time: 1000 mg ÷ 10 mg/min = 100 minutes
• Volume needed: 1000 mg ÷ (1000 mg / 20 mL) = 20 mL per dose (Stanford Health Care, 2023).

Trough Level Interpretation

• Trough level drawn 30 minutes before 4th dose: 9 mcg/mL
• Target trough:
  • For serious infections: 15–20 mcg/mL
  • For uncomplicated infections: 10–15 mcg/mL
• Analysis: 9 mcg/mL is sub-therapeutic for most indications. The dose should be increased to achieve the target trough.

IV Route

Vancomycin is given intravenously because the IV route ensures therapeutic serum levels for bloodstream, lung, bone, and other systemic infections (Patel et al., 2024). Notably, IV vancomycin is used for systemic infections due to poor oral absorption: vancomycin is not absorbed well from the GI tract. On the other hand, oral vancomycin is reserved for localized GI infections like Clostridioides difficile colitis.

Medication Order

• Vancomycin 1000 mg IV q12h
• Dispense: 20 mL vial; Infuse over 100 min
• Monitor trough levels; increase dose if <10 mcg/mL (Rybak et al., 2020).

References

CDC. (2021). Gonococcal infections among adolescents and adults. CDC – Sexually Transmitted Infections Treatment Guidelines, 2021. https://www.cdc.gov/std/treatment-guidelines/gonorrhea-adults.htm

Crader, M. F., Johns, T., & Arnold, J. K. (2023, May 1). Warfarin drug interactions. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK441964/

Curtis, K. M., Nguyen, A. T., Tepper, N. K., Zapata, L. B., Snyder, E. M., Hatfield-Timajchy, K., Kortsmit, K., Cohen, M. A., Whiteman, M. K., Baker, C., Dethier, D., Garbarino, S., Gold, H., Halper, E., Kapp, N., Krishna, G., Meurice, M., Ramer, S., Rodenhizer, J., . . . Wright, S. (2024). U.S. selected practice recommendations for contraceptive use, 2024. MMWR Recommendations and Reports, 73(3), 1–77. https://doi.org/10.15585/mmwr.rr7303a1

Kholmukhamedov, A., Subbotin, D., Gorin, A., & Ilyassov, R. (2025). Anticoagulation management: Current landscape and future trends. Journal of Clinical Medicine, 14(5), 1647. https://doi.org/10.3390/jcm14051647

Mohseni, M., Sung, S., & Takov, V. (2023, August 8). Chlamydia. National Library of Medicine; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK537286/

Ng, M., & Baradhi, K. M. (2024). Benign prostatic hyperplasia. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK558920/

Patel, S., Preuss, C. V., & Bernice, F. (2024, October 29). Vancomycin. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK459263/

Podder, V., & Sadiq, N. M. (2024). Levofloxacin. In www.ncbi.nlm.nih.gov. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK545180/

Public Health Agency of Canada. (2025, May 14). Gonorrhea guide: Treatment and follow-up. Canada.ca. https://www.canada.ca/en/public-health/services/infectious-diseases/sexual-health-sexually-transmitted-infections/canadian-guidelines/gonorrhea/treatment-follow-up.html

Rybak, M. J., Le, J., Lodise, T. P., Levine, D. P., Bradley, J. S., Liu, C., Mueller, B. A., Pai, M. P., Wong-Beringer, A., Rotschafer, J. C., Rodvold, K. A., Maples, H. D., & Lomaestro, B. M. (2020). Therapeutic monitoring of vancomycin for serious methicillin-resistant Staphylococcus aureus infections: A revised consensus guideline and review by the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the Society of Infectious Diseases Pharmacists. American Journal of Health-System Pharmacy, 77(11), 835–864. https://doi.org/10.1093/ajhp/zxaa036

Springer, C., & Salen, P. (2023). Gonorrhea. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK558903/

Stanford Health Care. (2023, February 22). SHC vancomycin dosing guide. https://med.stanford.edu/content/dam/sm/bugsanddrugs/documents/antimicrobial-dosing-protocols/SHC%20Vancomycin%20Dosing%20Guide.pdf

Waheed, S. M., Kudaravalli, P., & Hotwagner, D. T. (2023, January 19). Deep venous thrombosis. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK507708/

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Case studies are a useful way for you to apply your knowledge of pharmacokinetics and pharmacodynamic aspects of pharmacology to specific patient cases and health histories.

For this Assignment, you evaluate drug treatment plans for patients with various disorders and justify drug therapy plans based on patient history and diagnosis.

Resources

Be sure to review the Learning Resources before completing this activity.
Click the weekly resources link to access the resources.

WEEKLY RESOURCES

• Rosenthal, L. D., & Burchum, J. R. (2021). Lehne’s pharmacotherapeutics for advanced practice nurses and physician assistants (2nd ed.). Elsevier.
  • Chapters 50, “Estrogens and Progestins: Basic Pharmacology and Noncontraceptive Applications” (pp. 425a–436)
  • Chapter 51, “Birth Control” (pp. 437–446)
  • Chapter 52, “Androgens” (pp. 447a–453)
  • Chapter 53, “Male Sexual Dysfunction and Benign Prostatic Hyperplasia” (pp. 454–466)
  • Chapter 82, “Drug Therapy for Sexually Transmitted Diseases” (pp. 763–770)
  • Chapter 87, “Drugs for the Eye” (pp. 823a–833)
  • Chapter 88, “Drugs for the Skin” (pp. 834–848)
  • Chapter 89, “Drugs for the Ear” (pp. 849–856)

To Prepare:

• Review the case study posted in “Announcements” by your Instructor for this Assignment
• Review the information provided and answer questions posed in the case study
• When recommending a medication, write out a complete prescription for the medication
• Whenever possible, use clinical practice guidelines in developing your answers when possible
• Include at least three references to support your answer and cite them in APA format
• Submit your Assignment by Day 7 of Week 7 (Sunday night, 11:59 pm ET).
• Case studies are a useful way for you to apply your knowledge of pharmacokinetic and pharmacodynamic aspects of pharmacology to specific patient cases and health histories.
• For your week 9 assignment, evaluate drug treatment plans for patients with various disorders and justify drug therapy plans based on patient history and diagnosis.
• DIRECTIONS
• For each of the scenarios below, answer the questions using your learning resources, Medscape, and clinical practice guidelines (ie JNC 8, AHA, ACC etc). Lecturio is an optional resource but highly recommended. Be sure to thoroughly answer ALL questions. When recommending medications, write out a complete medication order. What would you send to a pharmacy? Include drug, dose, route, frequency, special instructions, # dispensed (days supply) and refill information. Also state if you would continue, discontinue or taper the patient’s current medications. Review and discuss ALL labs and possible interactions. Use at least 3 sources for each scenario and cite sources using APA format; include in-text citations. You do not need an introduction or conclusion paragraph. Please also review assignment rubric.
• ASSIGNMENT (covers weeks 9-11)
• SCENARIO 1
• What are the errors in the following prescriptions (5 total)? Rewrite each prescription correctly. What is each medication classification? What is the mechanism of action (MOA)?
• tamsulosin 4 mg po daily, 30 minutes after the same meal each day #30 2 RF
• levofloxcin 750 mg po daily for 5 days #5 0 RF
• ciprofloxacin 0.3% otic solution for bacterial conjunctivitis; instill 1-2 drops into eye every 2 hours while awake for 2 days then 1-2 drops every 4 hours while awake for the next 5 days #1 bottle 0 RF
• Paxlovid 300 mg ritonavir plus 100 mg nirmatrelvir po BID x 5 days #1 dose pack 0 RF
• Depo-Provera 150 mg IM inject once monthly #1 3 RF

SCENARIO 2

• FS is a 26-year-old sexually active female who presents with a 5-day history of yellow vaginal discharge, pelvic discomfort, and burning with urination. She reports unprotected intercourse with a new male partner over the past month. A gonorrhea culture returns positive. FS has documented allergies to latex and penicillin. What is the recommended first-line treatment for gonorrhea in this patient? What additional sexually transmitted infection should be empirically treated, and with which medication? Provide complete medication orders. How long should she abstain from sex to avoid reinfection, and what patient education should be provided?

SCENARIO 3

• JH is a 68-year-old male recently discharged from the hospital following a diagnosis of deep vein thrombosis (DVT). He was started on warfarin 5 mg PO daily with INR monitoring. At his follow-up clinic visit 6 days post-discharge, he reports that his primary care provider prescribed Bactrim DS (sulfamethoxazole/trimethoprim 800/160 mg) twice daily for 7 days to treat a urinary tract infection. Today, his INR is 6.9. He has minor bruising on his arms but no active bleeding. Additional medications include sertraline 100 mg po daily for depression and lisinopril 10 mg po daily for hypertension. What is the mechanism behind this interaction? How should JH’s medication therapy be adjusted?
• SCENARIO 4
• A patient is prescribed vancomycin 15 mg/kg IV every 12 hours for a 70 kg patient. The pharmacy stocks vancomycin 1 g per 20 mL vials.
• How much vancomycin (mg) should be administered per dose?
• How many milliliters of vancomycin solution should be drawn up for each dose?
• If the infusion rate is 10 mg/min, how long will it take to administer one dose?
• A trough level is drawn 30 minutes before the 4^th dose, and the result is 9 mcg/mL. Is the current dosing regimen appropriate based on the trough level? Would you increase, decrease, or leave the dose the same?
• Why is vancomycin usually given IV and not PO?