Question

UTI – Trimethoprim-sulfamethoxazole

RM a 46-year old woman, has a sever urinary tract infection. She is taking trimethoprim-sulfamethoxazole (Bactrim) 160 mg/800 mg every 6 hours.

1. Is the dose within the recommended drug dose and dosing interval? What is the nurse’s responsibility?

2. What are the similarities and differences between trimethoprim-sulfamethoxazole and sulfadiazine?

3. What are the signs of thrombocytopenia, hemolytic anemia, and agranulocytosis for patients who take high doses of sulfonamides?

4. Explain the assessment and nursing interventions regarding these severe adverse reactions to sulfonamides.

5. Patient teaching is an important part of nursing interventions. Explain the nurse’s role regarding patient teaching concerning the following:

A. What is the required amount of daily fluid intake?

B. What are the cross-sensitive effects if a patient is allergic to other sulfonamide preparations? What allergic reactions may occur?

C. What time of the day should sulfonamides be taken?

D. Why should bruising and bleeding be reported?

E. What protective measures should be taken to prevent possible photosensitivity?

RM takes the anticoagulant warfarin (Coumadin) 7.5 mg daily.

6. What effect does trimethoprim-sulfamethoxazole have on warfarin?

7. Should RM’s warfarin dosage be increased or decreased? Explain your answer.

Answer 1

ANSWER :

1) The dose is in the recommended drug dose but the dosing interval is incorrect.

Correct dose and dosage interval :

• Trimethoprim/Sulfamethoxazole 160/ 800 mg PO every 12 hours or twice daily for 3 days.

Nurse responsibilities :

• She should assess the patient clinical history , signs and symptoms.
• Change the drug dosage interval as high doses of sulfadiazines has many side effects.
• Assess the signs and symptoms of sulfadiazones toxicity and treat her accordingly.

2)Similarities :

• Antibiotics used to treat bacterial infections(UTI)
• Sulfadiazine + Pyrimethamine and Trimethoprim/Sulmethoxazole used in treatment of Toxoplasmosis.
• Their mechanism of action to kill bacteria is to inhibit folate synthesis pathway at various levels.

DIfferences :

Though they inhibit folate synthesis pathway , they inhibit it at various levels.

FOLATE SYNTHESIS PATHWAY DIHYDROP TEROATE DIPHOSPHATE P-AMINOBENZOICAUD (PABA) DIHYDROPTERUATS SYNTHETASE (SULFONAMIDES) DIHYDROPTERICALID DIHYDRO POLICACID DIHYDROPULATE REDUCTASE < (TRIMETHOPRINO) TETRA HYDO FOLICACIO

In the above flow chart can see that sulfonamides (Sulfadiazine and Sulfamethoxazole) inhibit Dihydropteroate synthetase and Trimethoprim inhibit Dihydrofolate reductase.

So , when Trimethoprim / Sulfamethoxazole given together it has greater effect(inibits at 2 levels in the folate synthesis pathway) than giving Sulfadiazine alone(inhibits at only one level)

3) Signs of thrombocytopenia :

• Abnormal bleeding and easy bruising .
• Petechie( pin point red spots ) , purpura (large flat areas) and ecchymosis (very large flat areas)over the skin.

Signs of agranulocytosis :

• Decreased WBC count
• Fever ,malaise , sore throat , fatigue , painful mouth and anal ulcers.

Signs of Hemolytic anemia :

• Increased heart rate and dyspnea.
• Skin becomes pale
• Jaundice ( yellowish discoloration of skin and eyes)
• Dark coloured urine
• Weakness