Lari
Lari Uses, Dosage, Side Effects, Food Interaction and all others data.
Pyrimethamine is a folic acid antagonist structurally similar to trimethoprim. It inhibits parasitic dihydrofolate reductase, thus inhibiting vital tetrahydrofolic acid synthesis. It is active against pre-erythrocytic forms and is also a slow-acting schizontocide.
Pyrimethamine is an antiparasitic compound commonly used as an adjunct in the treatment of uncomplicated, chloroquine resistant, P. falciparum malaria. Pyrimethamine is a folic acid antagonist and the rationale for its therapeutic action is based on the differential requirement between host and parasite for nucleic acid precursors involved in growth. This activity is highly selective against plasmodia and Toxoplasma gondii. Pyrimethamine possesses blood schizonticidal and some tissue schizonticidal activity against malaria parasites of humans. However, the 4-amino-quinoline compounds are more effective against the erythrocytic schizonts. It does not destroy gametocytes, but arrests sporogony in the mosquito. The action of pyrimethamine against Toxoplasma gondii is greatly enhanced when used in conjunction with sulfonamides.
Sulfamethoxazole is a bacteriostatic sulfonamide antibiotic that interferes with folic acid synthesis in susceptible bacteria. It is generally given in combination with trimethoprim, which inhibits a sequential step in bacterial folic acid synthesis - these agents work synergistically to block two consecutive steps in the biosynthesis of nucleic acids and proteins which are necessary for bacterial growth and division, and using them in conjunction helps to slow the development of bacterial resistance. In this combination, sulfamethoxazole is useful for the treatment of a variety of bacterial infections, including those of the urinary, respiratory, and gastrointestinal tracts.
Sulfamethoxazole is a bacteriostatic sulfonamide antibiotic that inhibits a critical step in bacterial folate synthesis. It is generally given in combination with trimethoprim, a dihydrofolate reductase inhibitor, which inhibits the reduction of dihydrofolic acid to tetrahydrofolic acid. Studies have shown that bacterial resistance develops more slowly with the combination of the two drugs than with either trimethoprim or sulfamethoxazole alone, as together they inhibit sequential steps in the bacterial folate synthesis pathway.
Sulfonamides, including sulfamethoxazole, have been implicated in hypersensitivity reactions - these agents should be discontinued at the first sign of a developing rash, as this may signal the start of a more severe reaction such as Stevens-Johnson syndrome or toxic epidermal necrolysis. Sulfamethoxazole treatment may contribute to folate deficiency and should therefore be used with caution in patients at a higher risk of developing a deficiency. Hemolysis has been observed in patients with glucose-6-phosphate dehydrogenase deficiency who are using sulfamethoxazole/trimethoprim.
| Trade Name | Lari |
| Generic | Sulfamethoxazole + Pyrimethamine |
| Weight | 500mg, |
| Type | Tablet, Suspension |
| Therapeutic Class | |
| Manufacturer | Ipca Laboratories |
| Available Country | India |
| Last Updated: | September 19, 2023 at 7:00 am |
Uses
Treatment of Toxoplasmosis: Pyrimethamine is used for the treatment of toxoplasmosis when used conjointly with a sulfonamide, since synergism exists with this combination.
Treatment of Acute Malaria: Pyrimethamine is also used for the treatment of acute malaria. It should not be used alone to treat acute malaria. Fast-acting schizonticides such as chloroquine or quinine are used and preferable for the treatment of acute malaria. However, conjoint use of Pyrimethamine with a sulfonamide (e.g., sulfadoxine) will initiate transmission control and suppression of susceptible strains of plasmodia.
Chemoprophylaxis of Malaria: Pyrimethamine is used for the chemoprophylaxis of malaria due to susceptible strains of plasmodia. However, resistance to pyrimethamine is prevalent worldwide. It is not suitable as a prophylactic agent for travelers to most areas.
Sulfamethoxazole is an oral sulfonamide antibiotic, given in combination with trimethoprim, used to treat a variety of infections of the urinary tract, respiratory system, and gastrointestinal tract.
Sulfamethoxazole is indicated in combination with trimethoprim, in various formulations, for the following infections caused by bacteria with documented susceptibility: urinary tract infections, acute otitis media in pediatric patients (when clinically indicated), acute exacerbations of chronic bronchitis in adults, enteritis caused by susceptible Shigella, prophylaxis and treatment of Pneumocystis jiroveci pneumonia, and travelers' diarrhea caused by enterotoxigenic E. coli.
In Canada, additional indications include the adjunctive treatment of cholera, treatment of bacillary dysentery, nocardiosis, and second-line treatment of brucellosis in combination with gentamicin or rifampicin.
Lari is also used to associated treatment for these conditions: Plasmodium Infections, Toxoplasmosis, Acute MalariaAcute Exacerbation of Chronic Bronchitis (AECB) caused by susceptible bacteria, Acute Otitis Media caused by susceptible bacteria, Brucellosis, Dysentery, Bacillary, Nocardiosis, Pneumocystis Jirovecii Pneumonia, Urinary Tract Infection caused by susceptible bacteria, Susceptible Cholera, Susceptible Enteritis infectious caused by Shigella flexneri, Susceptible Enteritis infectious caused by Shigella sonnei, Susceptible Travelers' Diarrhea caused by Enterotoxigenic E. Coli (ETEC) Infection
How Lari works
Pyrimethamine inhibits the dihydrofolate reductase of plasmodia and thereby blocks the biosynthesis of purines and pyrimidines, which are essential for DNA synthesis and cell multiplication. This leads to failure of nuclear division at the time of schizont formation in erythrocytes and liver.
Sulfamethoxazole is a sulfonamide that inhibits bacterial dihydrofolic acid synthesis due to its structural similarity to an endogenous substrate, para-aminobenzoic acid (PABA). Most bacteria meet their need for folic acid by synthesizing it from PABA, as opposed to Animalia that require exogenous folic acid sources. Sulfamethoxazole competitively inhibits dihydropteroate synthase, the enzyme responsible for bacterial conversion of PABA to dihydrofolic acid. Inhibition of this pathway prevents the synthesis of tetrahydrofolate and, ultimately, the synthesis of bacterial purines and DNA, resulting in a bacteriostatic effect.
Dosage
Lari dosage
For Treatment of Toxoplasmosis: The dosage of Pyrimethamine for the treatment of toxoplasmosis must be carefully adjusted so as to provide maximum therapeutic effect and a minimum of side effects. At the dosage required, there is a marked variation in the tolerance to the drug. Young patients may tolerate higher doses than older individuals. Concurrent administration offolinic acidis strongly recommended in all patients.
The adultstartingdose is 50 to 75 mg of the drug daily, together with 1 to 4 g daily of a sulfonamide of the sulfapyrimidine type, e.g. sulfadoxine. This dosage is ordinarily continued for 1 to 3 weeks, depending on the response of the patient and tolerance to therapy. The dosage may then be reduced to about one half that previously given for each drug and continued for an additional 4 to 5 weeks.
The pediatric dosage of Pyrimethamine is 1 mg/kg/day divided into 2 equal daily doses; after 2 to 4 days this dose may be reduced to one half and continued for approximately 1 month. The usual pediatric sulfonamide dosage is used in conjunction with Pyrimethamine.
For Treatment of Acute Malaria: Pyrimethamine is NOT recommended alone in the treatment of acute malaria. Fast-acting schizonticides, such as chloroquine or quinine, are indicated for treatment of acute malaria. However, Pyrimethamine at a dosage of 25 mg daily for 2 days with a sulfonamide will initiate transmission control and suppression of non-falciparum malaria.Pyrimethamine is only recommended for patients infected in areas where susceptible plasmodia exist. Should circumstances arise wherein Pyrimethamine must be used alone in semi- immune persons, the adult dosage for acute malaria is 50 mg for 2 days; children 4 through 10 years old may be given 25 mg daily for 2 days. In any event, clinical cure should be followed by the once-weekly regimen described below for chemoprophylaxis. Regimens which include suppression should be extended through any characteristic periods of earlyrecrudescenceand late relapse, i.e., for at least 10 weeks in each case.
For Chemoprophylaxis of Malaria:
- Adults and pediatric patients over 10 years: 25 mg (1 tablet) once weekly
- Children 4 through 10 years:12.5 mg (½ tablet) once weekly
- Infants and children under 4 years: 6.25 mg (¼ tablet) once weekly.
Side Effects
Hypersensitivity reactions, occasionally severe (such as Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, and anaphylaxis), and hyperphenylalaninemia, can occur particularly when pyrimethamine is administered concomitantly with a sulfonamide. Consult the complete prescribing information for the relevant sulfonamide for sulfonamideassociated adverse events. With doses of pyrimethamine used for the treatment of toxoplasmosis, anorexia and vomiting may occur. Vomiting may be minimized by giving the medication with meals; it usually disappears promptly upon reduction of dosage. Doses used in toxoplasmosis may produce megaloblastic anemia, leukopenia, thrombocytopenia, pancytopenia, neutropenia, atrophic glossitis, hematuria, and disorders of cardiac rhythm.
Toxicity
The oral LD50 of sulfamethoxazole in mice and rats is 2300 mg/kg and 6200 mg/kg, respectively.
Signs or symptoms of sulfonamide overdose include anorexia, colic, nausea, vomiting, dizziness, headache, drowsiness, and unconsciousness. Less common symptoms may include pyrexia, hematuria, and crystalluria. Later manifestations of overdose may include blood dyscrasias and jaundice. Treatment should be symptomatic and supportive, and may include gastric lavage or forced emesis if applicable. Monitor patient lab work for evidence of blood dyscrasias or electrolyte imbalances.
Precaution
The recommended dosage for chemoprophylaxis of malaria should not be exceeded. Pyrimethamine should be used with caution in patients with impaired renal or hepatic function or in patients with possible folate deficiency, such as individuals with malabsorption syndrome, alcoholism, or pregnancy, and those receiving therapy, such as phenytoin, affecting folate levels
Interaction
Pyrimethamine may be used with sulfonamides, quinine and other antimalarials, and with other antibiotics. However, the concomitant use of other antifolic drugs or agents associated with myelosuppression including sulfonamides or trimethoprim-sulfamethoxazole combinations, proguanil, zidovudine, or cytostatic agents (e.g., methotrexate), while the patient is receiving pyrimethamine, may increase the risk of bone marrow suppression. If signs of folate deficiency develop, pyrimethamine should be discontinued. Folinic acid (leucovorin) should be administered until normal hematopoiesis is restored
Volume of Distribution
The volume of distribution sulfamethoxazole following a single oral dose was found to be 13 L. Sulfamethoxazole distributes into sputum, vaginal fluid, middle ear fluid, breast milk, and the placenta.
Elimination Route
Well absorbed with peak levels occurring between 2 to 6 hours following administration
Sulfamethoxazole is rapidly absorbed following oral administration and has a bioavailability of 85-90%. The Tmax is approximately 1-4 hours following oral administration, and the Cmax at steady-state is 57.4 - 68.0 μg/mL.
Half Life
96 hours
The average serum half-life of sulfamethoxazole is 10 hours and may be increased in patients with severely impaired renal function.
Clearance
The oral and renal clearance of sulfamethoxazole have been estimated as 1.2 ± 0.2 and 0.22 ± 0.05 L/h, respectively.
Elimination Route
Elimination occurs primarily via glomerular filtration and tubular secretion in the kidneys, with urine concentrations generally considerably higher than plasma concentrations. Approximately 84.5% of a single oral dose of sulfamethoxazole is recovered in the urine within 72 hours, of which ~30% is free sulfamethoxazole and the remainder is the N4-acetylated metabolite.
Pregnancy & Breastfeeding use
Pregnancy Category C. Pyrimethamine has been shown to be teratogenic in rats when given in oral doses 7 times the human dose for chemoprophylaxis of malaria or 2.5 times the human dose for treatment of toxoplasmosis. At these doses in rats, there was a significant increase in abnormalities such as cleft palate, brachygnathia, oligodactyly, and microphthalmia. Pyrimethamine has also been shown to produce terata such as meningocele in hamsters and cleft palate in miniature pigs when given in oral doses 170 and 5 times the human dose, respectively, for chemoprophylaxis of malaria or for treatment of toxoplasmosis.
There are no adequate and well-controlled studies in pregnant women. Pyrimethamine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Concurrent administration of folinic acid is strongly recommended when used for the treatment of toxoplasmosis during pregnancy.
Nursing Mothers: Pyrimethamine is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from pyrimethamine and from concurrent use of a sulfonamide with Pyrimethamine for treatment of some patients with toxoplasmosis, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother
Contraindication
Use of Pyrimethamine is contraindicated in patients with known hypersensitivity to pyrimethamine or to any component of the formulation. Use of the drug is also contraindicated in patients with documented megaloblastic anemia due to folate deficiency.
Special Warning
Geriatric Use: Clinical studies of Pyrimethamine did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
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