Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: Is metabolite a drug?
An active metabolite is an active form of a drug after it has been processed by the body.
As in the previous case it is possible to find paradoxical situations where an active metabolite causes the drug's effect. In this case the increase in active metabolite A (following the previous example) produces an increase in the drug's effect.
The first pass through the hepatic portal vein results in some of the drug being metabolized by O-demethylation into an active metabolite of dextromethorphan called dextrorphan (DXO). DXO is the 3-hydroxy derivative of dextromethorphan. The therapeutic activity of dextromethorphan is believed to be caused by both the drug and this metabolite. Dextromethorphan also undergoes N-demethylation (to 3-methoxymorphinan or MEM), and partial conjugation with glucuronic acid and sulfate ions. Hours after dextromethorphan therapy, (in humans) the metabolites (+)-3-hydroxy-N-methylmorphinan, (+)-3-morphinan, and traces of the unchanged drug are detectable in the urine.
Levomethadyl acetate undergoes extensive first-pass metabolism to the active demethylated metabolite nor-LAAM, which is further demethylated to a second active metabolite, dinor-LAAM. These metabolites are more potent than the parent drug.
Secondary metabolites are organic compounds produced by bacteria, fungi, or plants which are not directly involved in the normal growth, development, or reproduction of the organism. Unlike primary metabolites, absence of secondary metabolites does not result in immediate death, but rather in long-term impairment of the organism's survivability, fecundity, or aesthetics, or perhaps in no significant change at all. Specific secondary metabolites are often restricted to a narrow set of species within a phylogenetic group. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses. Humans use secondary metabolites as medicines, flavorings, pigments, and recreational drugs.
Like other SCARs-inducing drugs, DRESS syndrome-inducing drugs or their metabolites stimulate CD8 T or CD4 T cells to initiate autoimmune responses. Studies indicate that the mechanism by which a drug or its metabolites accomplishes this stimulation involves subverting the antigen presentation pathways of the innate immune system. The drug or metabolite covalently binds with a host protein to form a non-self, drug-related epitope. An antigen presenting cell (APC) takes up these alter proteins; digests them into small peptides; places the peptides in a groove on the human leukocyte antigen (i.e. HLA) component of their major histocompatibility complex (i.e. MHC); and presents the MHC-associated peptides to the T-cell receptor on CD8 T or CD4 T cells. Those peptides expressing a drug-related, non-self epitope on their HLA-A, HLA-B, HLA-C, HLA-DM, HLA-DO, HLA-DP, HLA-DQ, or HLA-DR proteins may bind to a T-cell receptor to stimulate the receptor-bearing parent T cell to initiate attacks on self tissues. Alternatively, a drug or metabolite may stimulate these T cells by inserting into the groove on a HLA protein to serve as a non-self epitope or bind outside of this groove to alter a HLA protein so that it forms a non-self epitope. Importantly, however, non-self epitopes must bind to specific HLA serotypes in order to stimulate T cells. Since the human population expresses some 13,000 different HLA serotypes while an individual expresses only a fraction of them and since a DRESSs-inducing drug or metabolite interacts with only one or a few HLA serotypes, a drug's ability to induce SCARs is limited to those individuals who express HLA serotypes targeted by the drug or its metabolite. Thus, only rare individuals are predisposed to develop SCARs in response to a particular drug on the bases of their expression of HLA serotypes. Studies have identified several HLA serotypes associated with development of the DRESS syndrome in response to certain drugs, have developed tests to identify individuals who express some of these serotypes, and thereby have identified individuals who should avoid certain DRESS syndrome-inducing drugs.
Metabolites from chemical compounds, whether inherent or pharmaceutical, are formed as part of the natural biochemical process of degrading and eliminating the compounds.[2] The rate of degradation of a compound is an important determinant of the duration and intensity of its action. Profiling metabolites of pharmaceutical compounds, drug metabolism, is an important part of drug discovery, leading to an understanding of any undesirable side effects.
Diazepam undergoes oxidative metabolism by demethylation (CYP 2C9, 2C19, 2B6, 3A4, and 3A5), hydroxylation (CYP 3A4 and 2C19) and glucuronidation in the liver as part of the cytochrome P450 enzyme system. It has several pharmacologically active metabolites. The main active metabolite of diazepam is desmethyldiazepam (also known as nordazepam or nordiazepam). Its other active metabolites include the minor active metabolites temazepam and oxazepam. These metabolites are conjugated with glucuronide, and are excreted primarily in the urine. Because of these active metabolites, the serum values of diazepam alone are not useful in predicting the effects of the drug. Diazepam has a biphasic half-life of about one to three days, and two to seven days for the active metabolite desmethyldiazepam. Most of the drug is metabolised; very little diazepam is excreted unchanged. The elimination half-life of diazepam and also the active metabolite desmethyldiazepam increases significantly in the elderly, which may result in prolonged action, as well as accumulation of the drug during repeated administration.
AGEP also differs from the other SCARs disorders in respect to the level of evidence supporting the underlying mechanism by which a drug or its metabolite stimulates CD8 T or CD4 T cells. Studies indicate that the mechanism by which a drug or its metabolites accomplishes this stimulation involves subverting the antigen presentation pathways of the innate immune system. A drug or metabolite covalently binds with a host protein to form a non-self, drug-related epitope. An antigen presenting cell (APC) takes up these proteins; digests them into small peptides; places the peptides in a groove on the human leukocyte antigen (i.e. HLA) component of their major histocompatibility complex (i.e. MHC) (APC); and presents the MHC-associated peptides to the T-cell receptor on CD8 T or CD4 T cells. Those peptides expressing a drug-related, non-self epitope on their HLA-A, HLA-B, HLA-C, HLA-DM, HLA-DO, HLA-DP, HLA-DQ, or HLA-DR proteins may bind to a T-cell receptor to stimulate the receptor-bearing parent T cell to attack self tissues. Alternatively, a drug or metabolite may also stimulate T cells by inserting into the groove on a HLA protein to serve as a non-self epitope, bind outside of this groove to alter a HLA protein so that it forms a non-self epitope, or bypass the APC by binding directly to a T cell receptor. However, non-self epitopes must bind to specific HLA serotypes to stimulate T cells and the human population expresses some 13,000 different HLA serotypes while an individual expresses only a fraction of them. Since a SCARs-inducing drug or metabolite interacts with only one or a few HLA serotypes, their ability to induce SCARs is limited to those individuals who express HLA serotypes targeted by the drug or metabolite. Thus, only rare individuals are predisposed to develop SCARs in response to a particular drug on the bases of their expression of HLA serotypes. Studies have identified several HLA serotypes associated with development of DRESS syndrome, SJS, SJS/TEN, and TEN in response to various drugs which elici these disorders, developed tests to identify individuals who express these serotypes, and thereby determined that these individuals should avoid the offending drug. HLA serotypes associated with AGEP and specific drugs have not been identified. A study conducted in 1995 identified of HLA-B51, HLA-DR11, and HLA-DQ3 of unknown serotypes to be associated with development of AGEP but the results have not been confirmed, expanded to identify the serotypes involved, nor therefore useful in identifying individuals predisposed to develop AGEP in response to any drug. Similarly, a specific T cell receptor variant has been associated with the development of DRESS syndrome, SJS, SJS/TEN, and TEN but not AGEP.
Loteprednol etabonate was developed using retrometabolic drug design. It is a so-called soft drug, meaning its structure was designed so that it is predictably metabolised to inactive substances. These metabolites, Δ-cortienic acid and its etabonate, are derivatives of cortienic acid, itself an inactive metabolite of hydrocortisone.
It is specifically in the oxazaphosphorine group of medications.
Cyclophosphamide metabolites are primarily excreted in the urine unchanged, and drug dosing should be appropriately adjusted in the setting of renal dysfunction. Drugs altering hepatic microsomal enzyme activity (e.g., alcohol, barbiturates, rifampicin, or phenytoin) may result in accelerated metabolism of cyclophosphamide into its active metabolites, increasing both pharmacologic and toxic effects of the drug; alternatively, drugs that inhibit hepatic microsomal enzymes (e.g. corticosteroids, tricyclic antidepressants, or allopurinol) result in slower conversion of cyclophosphamide into its metabolites and consequently reduced therapeutic and toxic effects.
Flumequine is considered to be well absorbed and is excreted in the urine and feces as the glucuronide conjugates of the parent drug and 7-hydroxyflumequine. It is eliminated within 168 hours post-dosing. However, studies concerning the calf liver showed additional unidentified residues, of which a new metabolite, ml, represented the major single metabolite 24 hours after the last dose and at all subsequent time points. The metabolite ml, which exhibited no antimicrobial activity, was present in both free and protein-bound fractions. The major residue found in the edible tissues of sheep, pigs, and chickens was parent drug together with minor amounts of the 7-hydroxy-metabolite. The only detected residue in trout was the parent drug.
The metabolism of a drug or toxin in a body is an example of a biotransformation. The body typically deals with a foreign compound by making it more water-soluble, to increase the rate of its excretion through the urine. There are many different processes that can occur; the pathways of drug metabolism can be divided into:
Drugs can undergo one of four potential biotransformations: Active Drug to Inactive Metabolite, Active Drug to Active Metabolite, Inactive Drug to Active Metabolite, Active Drug to Toxic Metabolite (biotoxification).
Biotransformation of various pollutants is a sustainable way to clean up contaminated environments. These bioremediation and biotransformation methods harness the naturally occurring, microbial catabolic diversity to degrade, transform or accumulate a huge range of compounds including hydrocarbons (e.g. oil), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceutical substances, radionuclides and metals. Major methodological breakthroughs in recent years have enabled detailed genomic, metagenomic, proteomic, bioinformatic and other high-throughput analyses of environmentally relevant microorganisms providing unprecedented insights into biotransformation and biodegradative pathways and the ability of organisms to adapt to changing environmental conditions.
Bioanalysis is a sub-discipline of analytical chemistry covering the quantitative measurement of xenobiotics (drugs and their metabolites, and biological molecules in unnatural locations or concentrations) and biotics (macromolecules, proteins, DNA, large molecule drugs, metabolites) in biological systems.
The Human Metabolome Database is a freely available, open-access database containing detailed data on more than 40,000 metabolites that have already been identified or are likely to be found in the human body. The HMDB contains three kinds of information: 1) chemical information, 2) clinical information, and 3) biochemical information. The chemical data includes >40,000 metabolite structures with detailed descriptions, extensive chemical classifications, synthesis information and observed/calculated chemical properties. It also contains nearly 10,000 experimentally measured NMR, GC-MS and LC/MS spectra from more than 1100 different metabolites. The clinical information includes data on >10,000 metabolite-biofluid concentrations, metabolite concentration information on more than 600 different human diseases and pathway data for more than 200 different inborn errors of metabolism. The biochemical information includes nearly 6000 protein (and DNA) sequences and more than 5000 biochemical reactions that are linked to these metabolite entries. The HMDB supports a wide variety of online queries including text searches, chemical structure searches, sequence similarity searches and spectral similarity searches. This makes it particularly useful for metabolomic researchers who are attempting to identify or understand metabolites in clinical metabolomic studies. The first version of the HMDB was released in Jan. 1 2007 and was compiled by scientists at the University of Alberta and the University of Calgary. At that time they reported data on 2,500 metabolites, 1,200 drugs and 3,500 food components. Since then these scientists have greatly expanded the collection. The latest version of the HMDB (version 3.5) contains >16,000 endogenous metabolites, >1500 drugs and >22,000 food constituents or food metabolites.
The detection windows depend upon multiple factors: drug class, amount and frequency of use, metabolic rate, body mass, age, overall health, and urine pH. For ease of use, the detection times of metabolites have been incorporated into each parent drug. For example, heroin and cocaine can only be detected for a few hours after use, but their metabolites can be detected for several days in urine. The chart depicts the longer detection times of the metabolites.
Urine drug tests screen the urine for the presence of a parent drug or its metabolites. The level of drug or its metabolites is not predictive of when the drug was taken or how much the patient used. Rather, it is simply a confirmatory report indicating the presence of the parent drug or its metabolites.
The IdMOC system has numerous applications in drug development, such as the evaluation of drug metabolism and toxicity. It can simultaneously evaluate the toxic potential of a drug on cells from multiple organs and evaluate drug stability, distribution, metabolite formation, and efficacy. By modeling multiple-organ interactions, IdMOC can examine the pharmacological effects of a drug and its metabolites on target and off-target organs as well as evaluate drug-drug interactions by measuring cytochrome P450 (CYP) induction or inhibition in hepatocytes.
Compounds begin to break down as soon as they enter the body. The majority of small-molecule drug metabolism is carried out in the liver by redox enzymes, termed cytochrome P450 enzymes. As metabolism occurs, the initial (parent) compound is converted to new compounds called metabolites. When metabolites are pharmacologically inert, metabolism deactivates the administered dose of parent drug and this usually reduces the effects on the body. Metabolites may also be pharmacologically active, sometimes more so than the parent drug (see prodrug).
Individuals are predisposed to develop SCARs in response to a given drug based on the types of human leukocyte antigen (i.e. HLA) proteins and T cell receptors that they express; their ability to process an instigating drug or the drug's metabolite(s); and other less well-defined factors. These predispositions are a consequence of the HLA allele and T cell receptor variants that individuals express in their antigen presentation immune pathways; their ADME, i.e. efficiency in Absorbing, Distributing to tissues, Metabolizing, and/or Eliminating a drug or drug metabolite; and other less well-defined factors.
Rabeprazole is extensively metabolized by the liver. 90% of the drug is rendered into metabolites by the liver, which are then excreted by the kidneys. 10% of the dose is excreted in the feces. The drug metabolizing enzymes primarily responsible for rabeprazole's metabolism are CYP2C19 and CYP3A4. However, rabeprazole is mainly metabolized through non-enzymatic reduction to a thioether metabolite. Some of rabeprazole's metabolites include the following: a thioether carboxylic acid metabolite, a thioether glucuronide metabolite, and a sulfone metabolite. The most common metabolites excreted in the urine are the mercapturic acid conjugate and carboxylic acid. A diagram of rabeprazole's phase I metabolism is shown below.
Some researchers have suggested that hair drug testing for cocaine use should include testing for metabolites like norcocaine. The basis for this suggestion is the potential for external contamination of hair during testing. There is considerable debate about whether current means of washing hair samples are sufficient for removing external contamination. Some researchers state the methods are sufficient, while others state the residual contamination may result in a false positive test. Metabolites of cocaine, like norcocaine, in addition to cocaine, should be present in samples from drug users. Authors have stated that the metabolites should be present in any samples declared positive. Issues arise because the metabolites are present in only low concentrations. If the metabolites are present, it is possible for them to be from other contamination.
An active metabolite results when a drug is metabolized by the body into a modified form which continues to produce effects in the body. Usually these effects are similar to those of the parent drug but weaker, although they can still be significant (see e.g. 11-hydroxy-THC, morphine-6-glucuronide). Certain drugs such as codeine and tramadol have metabolites (morphine and O-desmethyltramadol respectively) that are stronger than the parent drug[1][2][3] and in these cases the metabolite may be responsible for much of the therapeutic action of the parent drug. Sometimes, however, metabolites may produce toxic effects and patients must be monitored carefully to ensure they do not build up in the body. This is an issue with some well-known drugs such as pethidine (meperidine) and dextropropoxyphene.[3][4]
Variations in ADME, i.e. an individuals efficiency in absorpting, distributing, metabolizing, and excreting a drug) has been found to occur in cases of the DRESS syndrome, SJS, SJS/TEN, and TEN. These variations influence the levels and duration of a drug or drug metabolite in tissues and thereby impact the drug's or drug metabolite's ability to evoke SCARs.
Variations in ADME, i.e. an individual's efficiency in absorbing, tissue-distributing, metabolizing, or excreting a drug, have been found to occur in various severe cutaneous adverse reactions (SCARS) as well as other types of adverse drug reactions. These variations influence the levels and duration of a drug or its metabolite in tissues and thereby impact the drug's or metabolite's ability to evoke these reactions. For example, CYP2C9 is an important drug-metabolizing cytochrome P450; it metabolizes and thereby inactivates phenytoin. Taiwanese, Japanese, and Malaysian individuals expressing the CYP2C9*3 variant of CYP2C9, which has reduced metabolic activity compared to the wild type (i.e. CYP2c9*1) cytochrome, have increased blood levels of phenytoin and an high incidence of SJS (as well as SJS/TEN and TEN) when taking the drug. In addition to abnormalities in drug-metabolizing enzymes, dysfunctions of the kidney, liver, or GI tract which increase a SCARs-inducing drug or metabolite levels are suggested to promote SCARs responses. These ADME abnormalities, it is also suggested, may interact with particular HLA proteins and T cell receptors to promote a SCARs disorder.