Clinical data | |
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Pronunciation | /ˌpɪrɪˈmɛθəmɪn/ |
Trade names | Daraprim, others |
AHFS/Drugs.com | Monograph |
MedlinePlus | a601050 |
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Routes of administration | By mouth |
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Pharmacokinetic data | |
Bioavailability | well-absorbed |
Protein binding | 87% |
Metabolism | Liver |
Elimination half-life | 96 hours |
Excretion | Kidney |
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CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.000.331 |
Chemical and physical data | |
Formula | C12H13ClN4 |
Molar mass | 248.71 g·mol−1 |
3D model (JSmol) | |
Melting point | 233 to 234 °C (451 to 453 °F) |
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Pyrimethamine, sold under the brand name Daraprim among others, is a medication used with leucovorin (leucovorin is used to decrease side effects of pyrimethamine; it does not have intrinsic anti-parasitic activity) to treat the parasitic diseases toxoplasmosis and cystoisosporiasis. [3] [4] It is also used with dapsone as a second-line option to prevent Pneumocystis jiroveci pneumonia in people with HIV/AIDS. [3] It was previously used for malaria but is no longer recommended due to resistance. [3] Pyrimethamine is taken by mouth. [3]
Common side effects include gastrointestinal upset, severe allergic reactions, and bone marrow suppression. [3] It should not be used by people with folate deficiency that has resulted in anemia. [3] There is concern that it may increase the risk of cancer. [3] While occasionally used in pregnancy it is unclear if pyrimethamine is safe for the baby. [1] Pyrimethamine is classified as a folic acid antagonist. [3] It works by inhibiting folic acid metabolism and therefore the making of DNA. [3]
Pyrimethamine was discovered in 1952 and came into medical use in 1953. [3] [5] It is on the World Health Organization's List of Essential Medicines. [6] It was approved as a generic in the United States in February 2020. [7]
Pyrimethamine is typically given with a sulfonamide and folinic acid. [8]
It is used for the treatment of toxoplasmosis, actinomycosis, and isosporiasis, and for the treatment and prevention of Pneumocystis jirovecii pneumonia. [3]
Pyrimethamine is also used in combination with sulfadiazine to treat active toxoplasmosis. The two drugs bind the same enzymatic targets as the drugs trimethoprim and sulfamethoxazole - dihydrofolate reductase and dihydropteroate synthase, respectively.[ citation needed ]
Pyrimethamine has also been used in several trials to treat retinochoroiditis. [9]
Pyrimethamine is labeled as pregnancy category C in the United States. [1] [10] To date, not enough evidence on its risks in pregnancy or its effects on the fetus is available. [10] [11]
It is primarily active against Plasmodium falciparum , but also against Plasmodium vivax . [12] Due to the emergence of pyrimethamine-resistant strains of P. falciparum, pyrimethamine alone is seldom used now. In combination with a long-acting sulfonamide such as sulfadiazine, it was widely used, such as in Fansidar, though resistance to this combination is increasing. [12]
Pyrimethamine is contraindicated in people with folate-deficiency anaemia. [8]
When higher doses are used, as in the treatment of toxoplasmosis, pyrimethamine can cause gastrointestinal symptoms such as nausea, vomiting, glossitis, anorexia, and diarrhea. [11] [13] A rash, which can be indicative of a hypersensitivity reaction, is also seen, particularly in combination with sulfonamides. [11] Central nervous system effects include ataxia, tremors, and seizures. [13] Hematologic side effects such as thrombocytopenia, leukopenia, and anemia can also occur. [13]
Other antifolate agents such as methotrexate and trimethoprim may potentiate the antifolate actions of pyrimethamine, leading to potential folate deficiency, anaemia, and other blood dyscrasias. [8]
Pyrimethamine interferes with the regeneration of tetrahydrofolic acid from dihydrofolate by competitively inhibiting the enzyme dihydrofolate reductase. [14] Tetrahydrofolic acid is essential for DNA and RNA synthesis in many species, including protozoa. [14] It has also been found to reduce the expression of SOD1, a key protein involved in amyotrophic lateral sclerosis. [15] [16]
Pyrimethamine is typically given with folinic acid and sulfadiazine. [10]
Resistance to pyrimethamine is widespread. Mutations in the malarial gene for dihydrofolate reductase may reduce its effectiveness. [17] These mutations decrease the binding affinity between pyrimethamine and dihydrofolate reductase via loss of hydrogen bonds and steric interactions. [18]
Nobel Prize-winning American scientist Gertrude Elion developed the drug at Burroughs-Wellcome (now part of GlaxoSmithKline) to combat malaria. [19] Pyrimethamine has been available since 1953. [20] In 2010, GlaxoSmithKline sold the marketing rights for Daraprim to CorePharma. Impax Laboratories sought to buy CorePharma in 2014, and completed the acquisition, including Daraprim, in March 2015. [21] In August 2015, the rights were bought by Turing Pharmaceuticals. [22] Turing subsequently became infamous for a price hike controversy when it raised the price of a dose of the drug in the U.S. market from US$13.50 to US$750, a 5,500% increase. [23]
In the United States in 2015, Turing Pharmaceuticals was criticized for increasing the price 50-fold, from US$13.50 to $750 a tablet, [24] leading to a cost of $75,000 for a course of treatment reported at one hospital. [25]
In the United States, in 2015, with Turing Pharmaceuticals' acquisition of the US marketing rights for Daraprim tablets, [26] Daraprim became a single-source and specialty pharmacy item, and the price was increased. [27] The cost of a monthly course for a person on 75 mg dose rose to about $75,000/month at one hospital, or $750 per tablet while it was previously priced at $13.50. [28]
Outpatients could no longer obtain the medication from a community pharmacy, but only through a single dispensing pharmacy, Walgreens Specialty Pharmacy, and institutions could no longer order from their general wholesaler, but had to set up an account with the Daraprim Direct program. [27] [29] Presentations from Retrophin, a company formerly headed by Martin Shkreli, CEO of Turing, from which Turing acquired the rights to Daraprim, suggested that a closed distribution system could prevent generic competitors from legally obtaining the drugs for the bioequivalence studies required for FDA approval of a generic drug. [29]
Shkreli defended the price hike by saying, "If there was a company that was selling an Aston Martin at the price of a bicycle, and we buy that company and we ask to charge Toyota prices, I don't think that that should be a crime." [30] [31] As a result of the backlash, Shkreli hired a crisis public relations firm to help explain his fund's move. [32] Turing Pharmaceuticals announced on 24 November 2015, "that it would not reduce the list price of that drug after all", but they would offer patient assistance programs. [33] New York Times journalist Andrew Pollack noted that these programs "are standard for companies selling extremely high-priced drugs. They enable the patients to get the drug while pushing most of the costs onto insurance companies and taxpayers." [33]
The price increase was criticized by physician groups such as HIV Medicine Associates and Infectious Diseases Society of America. [34]
In 2016, a group of high school students from Sydney Grammar supported by the University of Sydney prepared pyrimethamine as an illustration that the synthesis is comparatively easy and the price-hike unjustifiable. His team produced 3.7 g for US$20, which would have been worth between US$35,000 and US$110,000 in the United States at the time. [35] Shkreli said the schoolboys were not competition, likely because the necessary bioequivalence studies require a sample of the existing medication provided directly by the company, and not simply purchased from a pharmacy, which Turing could decline to provide. [36] [37] Nonetheless, the students' work was featured in The Guardian [36] and Time magazine, [38] and on ABC Australia, [35] the BBC, [37] and CNN. [39]
On 22 October 2015, Imprimis Pharmaceuticals announced it had made available compounded and customizable formulations of pyrimethamine and leucovorin in capsules to be taken by mouth starting as low as $99 for a 100-count bottle in the United States. [40] Pyrimethamine was approved as a generic in the United States in February 2020. [7]
In January 2020, the FTC filed a case against Vyera "alleging an elaborate anticompetitive scheme to preserve a monopoly for the life-saving drug, Daraprim". [41] A settlement was reached in December 2021. According to AP News, the settlement "requires Vyera and Phoenixus to provide up to $40 million in relief over 10 years to consumers who allegedly were fleeced by their actions and requires them to make Daraprim available to any potential generic competitor at the cost of producing the drug." [42] According to Law360, company executive Kevin Mulleady "agreed to a seven-year ban on working for or holding more than an 8% share in most pharmaceutical companies." [43]
In India, multiple combinations of generic pyrimethamine are available for a price ranging from US$0.04 to US$0.10 each (3–7 rupees). [44] [45] [46] [47]
In the UK, the same drug is available from GSK at a cost of US$20 (£13) for 30 tablets (about $0.66 each). [48]
In Australia, the drug is available in most pharmacies at a cost of US$9.35 (A$12.99) for 50 tablets (around US$0.18 each). [49]
In Brazil, the drug is available for R$0.07 a pill, or about US$0.02. [50]
In Switzerland, the drug is available for US$9.45 (CHF9.05) for 30 tablets (around US$0.32 a piece). [51]
In 2011, researchers discovered that pyrimethamine can increase β-hexosaminidase activity, thus potentially slowing down the progression of late-onset Tay–Sachs disease. [52] It is being evaluated in clinical trials as a treatment for amyotrophic lateral sclerosis. [53]
Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage. Folate is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division and maturation of blood cells. As the human body cannot make folate, it is required in the diet, making it an essential nutrient. It occurs naturally in many foods. The recommended adult daily intake of folate in the U.S. is 400 micrograms from foods or dietary supplements.
Trimethoprim (TMP) is an antibiotic used mainly in the treatment of bladder infections. Other uses include for middle ear infections and travelers' diarrhea. With sulfamethoxazole or dapsone it may be used for Pneumocystis pneumonia in people with HIV/AIDS. It is taken orally.
Sydney Grammar School is an independent, non-denominational day school for boys, located in Sydney, Australia.
Trimethoprim/sulfamethoxazole, sold under the brand name Bactrim among others, is a fixed-dose combination antibiotic medication used to treat a variety of bacterial infections. It consists of one part trimethoprim to five parts sulfamethoxazole. It is used to treat urinary tract infections, methicillin-resistant Staphylococcus aureus (MRSA) skin infections, travelers' diarrhea, respiratory tract infections, and cholera, among others. It is used both to treat and prevent pneumocystis pneumonia and toxoplasmosis in people with HIV/AIDS and other causes of immunosuppression. It can be given orally or intravenous infusion.
Folinic acid, also known as leucovorin, is a medication used to decrease the toxic effects of methotrexate and pyrimethamine. It is also used in combination with 5-fluorouracil to treat colorectal cancer and pancreatic cancer, may be used to treat folate deficiency that results in anemia, and methanol poisoning. It is taken by mouth, injection into a muscle, or injection into a vein.
Sulfamethoxazole is an antibiotic. It is used for bacterial infections such as urinary tract infections, bronchitis, and prostatitis and is effective against both gram negative and positive bacteria such as Escherichia coli and Listeria monocytogenes.
Aminopterin, the 4–amino derivative of folic acid, is an antineoplastic drug with immunosuppressive properties often used in chemotherapy. Aminopterin is a synthetic derivative of pterin. Aminopterin works as an enzyme inhibitor by competing for the folate binding site of the enzyme dihydrofolate reductase. Its binding affinity for dihydrofolate reductase effectively blocks tetrahydrofolate synthesis. This results in the depletion of nucleotide precursors and inhibition of DNA, RNA, and protein synthesis.
Pemetrexed, sold under the brand name Alimta among others, is a chemotherapy medication for the treatment of pleural mesothelioma and non-small cell lung cancer (NSCLC).
Etacrynic acid (INN) or ethacrynic acid (USAN), trade name Edecrin, is a loop diuretic used to treat high blood pressure and the swelling caused by diseases like congestive heart failure, liver failure, and kidney failure. A con with ethacrynic acid compared to the other loop diuretic drugs such as furosemide is that it has a significantly steep dose-response curve, which means the drug's dosing is very important as small variance in dose can cause a significant difference in the biological response.
Sulfadiazine is an antibiotic. Used together with pyrimethamine, a dihydrofolate reductase inhibitor, it is the treatment of choice for toxoplasmosis, which is caused by a protozoan parasite. It is a second-line treatment for otitis media, prophylaxis of rheumatic fever, chancroid, chlamydia, and infections by Haemophilus influenzae. It is also used as adjunct therapy for chloroquine-resistant malaria and several forms of bacterial meningitis. It is taken by mouth. Sulfadiazine is available in multiple generic tablets of 500 mg. For urinary tract infections, the usual dose is 4 to 6 grams daily in 3 to 6 divided doses.
Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a folic acid derivative.
Sulfadimethoxine is a long-lasting sulfonamide antimicrobial medication used in veterinary medicine. It is used to treat many infections, including respiratory, urinary tract, enteric, and soft tissue infections and can be given as a standalone or combined with ormetoprim to broaden the target range. Like all sulfamides, sulfadimethoxine inhibits bacterial synthesis of folic acid by acting as a competitive inhibitor against PABA. It is the most common drug prescribed to dogs who have coccidiosis.
Antifolates are a class of antimetabolite medications that antagonise (that is, block) the actions of folic acid (vitamin B9). Folic acid's primary function in the body is as a cofactor to various methyltransferases involved in serine, methionine, thymidine and purine biosynthesis. Consequently, antifolates inhibit cell division, DNA/RNA synthesis and repair and protein synthesis. Some such as proguanil, pyrimethamine and trimethoprim selectively inhibit folate's actions in microbial organisms such as bacteria, protozoa and fungi. The majority of antifolates work by inhibiting dihydrofolate reductase (DHFR).
Medication costs, also known as drug costs are a common health care cost for many people and health care systems. Prescription costs are the costs to the end consumer. Medication costs are influenced by multiple factors such as patents, stakeholder influence, and marketing expenses. A number of countries including Canada, parts of Europe, and Brazil use external reference pricing as a means to compare drug prices and to determine a base price for a particular medication. Other countries use pharmacoeconomics, which looks at the cost/benefit of a product in terms of quality of life, alternative treatments, and cost reduction or avoidance in other parts of the health care system. Structures like the UK's National Institute for Health and Clinical Excellence and to a lesser extent Canada's Common Drug Review evaluate products in this way.
Sulfadoxine/pyrimethamine, sold under the brand name Fansidar, is a combination medication used to treat malaria. It contains sulfadoxine and pyrimethamine. For the treatment of malaria it is typically used along with other antimalarial medication such as artesunate. In areas of Africa with moderate to high rates of malaria, three doses are recommended during the second and third trimester of pregnancy.
Martin Shkreli is an American investor and businessman. Shkreli is the co-founder of the hedge funds Elea Capital, MSMB Capital Management, and MSMB Healthcare, the co-founder and former CEO of pharmaceutical firms Retrophin and Turing Pharmaceuticals, and the former CEO of start-up software company Gödel Systems, which he founded in August 2016.
Vyera Pharmaceuticals is a pharmaceutical company incorporated in Zug, Switzerland, with offices in New York City. The company started to do business in the US as Vyera Pharmaceuticals in September 2017.
Harrow Health, Inc., formerly known as Imprimis Pharmaceuticals, is a publicly traded pharmaceutical company based in Nashville, Tennessee.
Alice Elizabeth Motion is a British chemist, science communicator, and associate professor at the School of Chemistry, University of Sydney. She is the founder of the Breaking Good project which encourages high school and undergraduate students to take part in research that can benefit human health. In 2018, the Breaking Good project was a finalist on the Google.org Impact Challenge.
Matthew Houghton Todd is a British chemist and the Professor and Chair of Drug Discovery of the School of Pharmacy at University College London. He is the founder of Open Source Malaria (OSM) and his research focuses on drug discovery and development for this disease. Recently, he has expanded to other areas, particularly neglected diseases such as tuberculosis and mycetoma in the Open Source Tuberculosis (OSTB) and Open Source Mycetoma (MycetOS) project, through a collaboration with the Drugs for Neglected Diseases Initiative and Erasmus MC. In addition, he has some research activity in catalysis and methodology.
Turing immediately raised the price to $750 a tablet from $13.50, bringing the annual cost of treatment for some patients to hundreds of thousands of dollars.
Heavy scrutiny followed, and although Turing agreed to reduce the price, the drug remains prohibitively expensive for many patients. Recently, at our hospital, an immigrant patient with a new diagnosis of HIV– AIDS and toxoplasmosis couldn't receive first-line therapy because of cost: the price for 100 pills was $75,000.