Methotrexate: Difference between revisions
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<Structure load='MTX' size='350' frame='true' align='right' caption='Methotrexate' scene='Insert optional scene name here' /> | <Structure load='MTX' size='350' frame='true' align='right' caption='Methotrexate' scene='Insert optional scene name here' /> | ||
Methotrexate, formerly known as amethopterin, is a drug that is used in the competitive inhibition of [[Dihydrofolate reductase]], resulting in decreased synthesis of dTTP and diminished cellular replication. The antimetabolic nature of methotrexate is most effective against the most rapidly dividing cells, making this drug useful in | Methotrexate, formerly known as amethopterin, is a drug that is used in the competitive inhibition of [[Dihydrofolate reductase]], resulting in decreased synthesis of dTTP and diminished cellular replication. The antimetabolic nature of methotrexate is most effective against the most rapidly dividing cells, making this drug useful in [[Cancer]] [[Pharmaceutial Drugs|treatment]], and various autoimmune diseases<ref>Methotrexate. (n.d.). UW Department of Orthopaedics and Sports Medicine - Patient Care. Retrieved March 10, 2011, from http://www.orthop.washington.edu/PatientCare/OurServices/Arthritis/Articles/Methotrexate.aspx </ref>. | ||
==Chemical Properties== | ==Chemical Properties== | ||
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Dosage size of methotrexate is extremely important because of the antimetabolic function of the drug, therefore many pharmacokinetic properties must be considered prior to treatment. Methotrexate is a dicarboxylic acid, although with a pKa of 4.8 and 5.5 is weak and often ionized in physiological conditions. Bioavailability following oral absorption is dose dependent, with 60 percent at doses lower than 30 mg/m2, and at concentrations above 80 mg/m2, there is only 20 percent bioavailability, percentages that can be increased with intramuscular administering of the drug. Only about 5 percent of the total loss of the oral dose is due to bacterial degradation. The kidney, spleen, liver, gallbladder, as well as the skin display the highest levels of methotrexate upon treatment. This drug does not cross the blood brain barrier efficiently, but the distribution to the kidney and liver may be prolonged with higher doses extending drug clearance time. Methotrexate can be metabolized through the liver and intracellular mechanisms, and the kidneys are capable of excreting from 80 to 90 percent of the drug without metabolizing methotrexate<ref>Methotrexate. (2010, September 1). CCO Formulary. Retrieved March 10, 2011, from www.cancercare.on.ca/pdfdrugs/methotre.pdf </ref>. | Dosage size of methotrexate is extremely important because of the antimetabolic function of the drug, therefore many pharmacokinetic properties must be considered prior to treatment. Methotrexate is a dicarboxylic acid, although with a pKa of 4.8 and 5.5 is weak and often ionized in physiological conditions. Bioavailability following oral absorption is dose dependent, with 60 percent at doses lower than 30 mg/m2, and at concentrations above 80 mg/m2, there is only 20 percent bioavailability, percentages that can be increased with intramuscular administering of the drug. Only about 5 percent of the total loss of the oral dose is due to bacterial degradation. The kidney, spleen, liver, gallbladder, as well as the skin display the highest levels of methotrexate upon treatment. This drug does not cross the blood brain barrier efficiently, but the distribution to the kidney and liver may be prolonged with higher doses extending drug clearance time. Methotrexate can be metabolized through the liver and intracellular mechanisms, and the kidneys are capable of excreting from 80 to 90 percent of the drug without metabolizing methotrexate<ref>Methotrexate. (2010, September 1). CCO Formulary. Retrieved March 10, 2011, from www.cancercare.on.ca/pdfdrugs/methotre.pdf </ref>. | ||
==Additional Information== | |||
For additional information see: [[Pharmaceutical Drugs]] | |||
== References == | == References == | ||
<references/> | <references/> | ||
