Home Drug Guide Pyrimethamine

Drug Guide

Generic Name

Pyrimethamine

Brand Names Daraprim

Classification

Therapeutic: Antiprotozoal agent, Antimalarial

Pharmacological: Diaminopyrimidine

FDA Approved Indications

  • Toxoplasmosis; Malaria (as part of combination therapy)

Mechanism of Action

Pyrimethamine inhibits dihydrofolate reductase, an enzyme involved in folic acid metabolism, thereby inhibiting DNA synthesis in protozoa.

Dosage and Administration

Adult: Varies based on indication; for toxoplasmosis, typical dosage is 75-100 mg initially, then maintenance doses of 25-50 mg daily for weeks to months.

Pediatric: Dose based on body weight; commonly 2.5 mg/kg per day, divided into doses.

Geriatric: Dose adjustments based on renal and hepatic function, increased monitoring recommended.

Renal Impairment: Use with caution; dose adjustments may be necessary.

Hepatic Impairment: Use with caution; monitor hepatic function.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed, crosses blood-brain barrier.

Metabolism: Minimal hepatic metabolism.

Excretion: Renal excretion; active metabolites may be excreted via the kidneys.

Half Life: Approximately 3-4 days.

Contraindications

  • Hypersensitivity to pyrimethamine or other sulfonamides.

Precautions

  • Blood dyscrasias (e.g., anemia, leukopenia), folic acid deficiency, hepatic and renal impairment, pregnancy (category C).

Adverse Reactions - Common

  • Nausea, vomiting (Common)
  • Rash (Common)

Adverse Reactions - Serious

  • Bone marrow suppression leading to anemia, leukopenia, thrombocytopenia (Rare but serious)
  • Stevens-Johnson syndrome, toxic epidermal necrolysis (Rare)

Drug-Drug Interactions

  • Sulfamethoxazole, other folate antagonists, drugs affecting bone marrow function.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor blood counts regularly (CBC), assess for hypersensitivity reactions.

Diagnoses:

  • Risk of infection due to bone marrow suppression.

Implementation: Administer with food to decrease gastrointestinal upset. Regularly monitor blood parameters.

Evaluation: Evaluate for signs of hypersensitivity, blood dyscrasias, and effectiveness in treating toxoplasmosis or malaria.

Patient/Family Teaching

  • Take medication exactly as prescribed.
  • Report signs of blood disorders, hypersensitivity, or skin reactions immediately.
  • Maintain proper hydration.
  • Use caution to avoid sun exposure due to photosensitivity.
  • Complete entire course of therapy.

Special Considerations

Black Box Warnings:

  • Bone marrow suppression and hypersensitivity reactions.

Genetic Factors: Individuals with G6PD deficiency may be at increased risk of hemolytic anemia.

Lab Test Interference: May cause false lab results in certain assays.

Overdose Management

Signs/Symptoms: Severe bone marrow suppression, gastrointestinal symptoms, neurological symptoms.

Treatment: Supportive care, folinic acid (leucovorin) may be administered to mitigate hematologic toxicity.

Storage and Handling

Storage: Store at room temperature (20-25°C); protect from moisture and light.

Stability: Stable under recommended conditions for the shelf life indicated.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.