Toxoplasmosis gondii population, actively invade the host cells by a mechanism conducted by the own parasite, named active invasion. In this process, the parasite secretes proteins from organelles like micronemes and rhoptries which will mediate the invasion
Name of the Drug Antiprotozoal Toxoplasmosis
- Pyrimethamine
| Pyrimethamine |
| Availability: Tablets: 25 mg |
| Indication & dosage : 1. To control plasmodia transmission and suppress susceptible strains Adults and children ages 10 and older: 25 mg P.O. daily for 2 days, given with a sulfonamide |
| 2. Toxoplasmosis Adults: Initially, 50 to 75 mg P.O. daily for 1 to 3 weeks, given with a sulfonamide. Depending on response and tolerance, reduce dosages of both drugs by 50% and continue therapy for 4 to 5 more weeks. Children: 1 mg/kg P.O. daily in two equally divided doses for 2 to 4 days, then reduced to 0.5 mg/kg/day for approximately 1 month. Alternatively, 2 mg/kg (up to 100 mg) P.O. daily in two equally divided doses for 3 days, then 1 mg/kg (up to 25 mg) in two equally divided doses for 4 weeks, given with sulfadiazine for 4 weeks. |
| 3. Prophylaxis of malaria caused by susceptible plasmodia strains Adults and children older than age 10: 25 mg P.O. weekly Children ages 4 to 10: 12.5 mg P.O. weekly Infants and children young |
| Mechanism of Action : Inhibits reduction of dihydrofolic acid to tetrahydrofolic acid (folinic acid) by binding to and reversibly inhibiting dihydrofolate reductase |
| Administration : ● Administer with meals. ● When giving tablets to young children, crush them and administer as oral suspension in water, cherry syrup, or sweetened solution. ● Know that because of worldwide resistance to pyrimethamine, its use alone to prevent or treat acute malaria is no longer recommended. ● Be aware that fixed combination of pyrimethamine and sulfadoxine is available and has been used for uncomplicated mild to moderate malaria caused by chloroquineresistant Plasmodium falciparum and for presumptive self-treatment by travelers. |
Metabolism & Elimination:
Metabolism: hepatic
Half-life elimination: 80-95 hr
Peak Plasma Time: 1.5-8 hr
Excretion: urine (20-30% as unchanged drug)
Contraindications
- Hypersensitivity to drug
- Megaloblastic anemia caused by folate deficiency
- Concurrent folate antagonist therapy
Precautions:
- anemia, bone marrow depression, hepatic or renal impairment, G6PD
- history of seizures
- patients more than 16 weeks pregnant
- breastfeeding patients.
Adverse reactions
- CNS: headache, light-headedness, insomnia, malaise, depression, seizures
- CV: arrhythmias
- ENT: dry throat
- GI: nausea, vomiting, diarrhoea, anorexia, atrophic glossitis
- GU: haematuria
- Hematologic: megaloblastic anaemia, leukopenia, pancytopenia, thrombocytopenia
- Metabolic: hyperphenylalaninemia
- Respiratory: pulmonary eosinophilia
- Skin: pigmentation changes, dermatitis, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome
- Other: fever, anaphylaxis
Patient monitoring
- Monitor CBC. Watch for evidence of blood dyscrasias.
- Assess for signs and symptoms of folic acid deficiency.
- Closely monitor neurologic and cardiovascular status. Stay alert for seizures and arrhythmias.
- Watch for evidence of erythema multiforme, including sore throat, cough, mouth sores, rash, iritic lesions, and fever. Report early signs before condition can progress to StevensJohnson syndrome.
Patient teaching
- Advise patient to take with meals.
- Tell patient to discontinue drug and contact prescriber at first sign of rash.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness. As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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