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Absorption half-life 1 h, elimination half-life 12 h. Biological half-life (elimination half-life, pharmacological half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration (C max) to half of C max in the blood plasma.
Methotrexate was originally developed and continues to be used for chemotherapy, either alone or in combination with other agents.It is effective for the treatment of several cancers, including solid tumours of breast, head and neck, lung, bladder, as well as acute lymphocytic leukemias, non-Hodgkin's lymphoma, osteosarcoma, and choriocarcinoma and other trophoblastic neoplasms.
An equianalgesic chart can be a useful tool, but the user must take care to correct for all relevant variables such as route of administration, cross tolerance, half-life and the bioavailability of a drug. [5] For example, the narcotic levorphanol is 4–8 times stronger than morphine, but also has a much longer half-life. Simply switching the ...
An effective half-life of the drug will involve a decay constant that represents the sum of the biological and physical decay constants, as in the formula: = + With the decay constant it is possible to calculate the effective half-life using the formula:
A drug's characteristics make a clear distinction between tissues with high and low blood flow. Enzymatic saturation: When the dose of a drug whose elimination depends on biotransformation is increased above a certain threshold the enzymes responsible for its metabolism become saturated. The drug's plasma concentration will then increase ...
For example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. The converse of half-life (in exponential growth) is doubling time. The original term, half-life period, dating to Ernest Rutherford's discovery of the principle in 1907, was shortened to half-life in the early 1950s. [1]
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods include jumping up and down make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds. [1]
In toxicology, the median lethal dose, LD 50 (abbreviation for "lethal dose, 50%"), LC 50 (lethal concentration, 50%) or LCt 50 is a toxic unit that measures the lethal dose of a given substance. [1]