出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2012/12/20 00:53:01」(JST)
Systematic (IUPAC) name | |
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1H-pyrazolo[3,4-d]pyrimidin-4(2H)-one | |
Clinical data | |
Trade names | Lopurin, Zyloprim |
AHFS/Drugs.com | monograph |
MedlinePlus | a682673 |
Pregnancy cat. | C(USA) |
Legal status | ℞-only (US) |
Routes | tablet (100, 300 mg) |
Pharmacokinetic data | |
Bioavailability | 78±20% |
Protein binding | Negligible |
Metabolism | hepatic (80% oxypurinol, 10% allopurinol ribosides) |
Half-life | 2 h (oxypurinol 18-30 h) |
Identifiers | |
CAS number | 315-30-0 Y |
ATC code | M04AA01 |
PubChem | CID 2094 |
DrugBank | DB00437 |
ChemSpider | 2010 Y |
UNII | 63CZ7GJN5I Y |
KEGG | D00224 Y |
ChEBI | CHEBI:40279 Y |
ChEMBL | CHEMBL1467 Y |
Chemical data | |
Formula | C5H4N4O |
Mol. mass | 136.112 g/mol |
SMILES
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InChI
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Y (what is this?) (verify) |
Allopurinol (Zyloprim, and generics) is a drug used primarily to treat hyperuricemia (excess uric acid in blood plasma) and its complications, including chronic gout.[1]
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Allopurinol is a purine analog; it is a structural isomer of hypoxanthine (a naturally occurring purine in the body) and is an inhibitor of the enzyme xanthine oxidase.[1] Xanthine oxidase is responsible for the successive oxidation of hypoxanthine and xanthine, resulting in the production of uric acid, the product of human purine metabolism.[1] In addition to blocking uric acid production, inhibition of xanthine oxidase causes an increase in hypoxanthine and xanthine. While xanthine cannot be converted to purine ribotides, hypoxanthine can be salvaged to the purine ribotides adenosine and guanosine monophosphates. Increased levels of these ribotides may cause feedback inhibition of amidophosphoribosyl transferase, the first and rate-limiting enzyme of purine biosynthesis. Allopurinol, therefore, decreases uric acid formation and may also inhibit purine synthesis.[2]
Allopurinol inhibits the breakdown (catabolism) of the thiopurine drug mercaptopurine, and it was specifically invented by Gertrude Elion to enhance the action of mercaptopurine in the treatment of acute lymphoblastic leukemia.[3] However, no improvement in leukemia response was noted with mercaptopurine-allopurinol co-therapy, and this use of the drug was abandoned.
Subsequently the uric acid lowering capacity of allopurinol was noted, and the drug went on to be developed for its more famous use: to treat hyperuricemia (excess uric acid in blood plasma) and its complications.[3] Allopurinol does not alleviate acute attacks of gout (and can actually make them worse initially), but is useful in chronic gout to prevent future attacks.
Allopurinol was also commonly used in chemotherapeutic treatments to treat 'tumor lysis syndrome' (as these regimes can rapidly produce severe acute hyperuricemia) although it has gradually been replaced by urate oxidase therapy.[4]
Allopurinol can cause severe pancytopenia if given with full-dose mercaptopurine or its pro-drug azathioprine, due to the inhibition of xanthine oxidase that metabolizes mercaptopurine.[5] For this reason, allopurinol has usually been contraindicated for thiopurine therapy. However, in recent years the use of allopurinol in combination with azathioprine or mercaptopurine has been revived. First, it was shown that an azathioprine/allopurinol combination significantly improved renal transplant graft survival.[6] More recently, it was discovered that this co-therapy greatly improves the outcome for patients that do not respond to thiopurine monotherapy when treating inflammatory bowel disease (IBD), specifically Crohn's disease.[7] Co-therapy has also been shown to greatly improve hepatoxicity side effects in treatment of IBD.[8] Co-therapy invariably requires dose reduction of the thiopurine, usually to 1/3 of the standard dose depending upon the patient's genetic status for thiopurine methyltransferase (TPMT).[9]
Other established indications for allopurinol therapy include ischemic reperfusion injury, kidney stones with a uric acid component (uric acid nephrolithiasis), and protozoal infections (Leishmaniasis).
Allopurinol can be used in patients with poor kidney function, but it may also help them. A study of allopurinol use in patients with chronic kidney disease suggested that "Allopurinol decreases C-reactive protein and slows down the progression of renal disease in patients with chronic kidney disease. In addition, allopurinol reduces cardiovascular and hospitalization risk in these subjects."[10]
A mechanistic study in patients with chronic heart failure has shown that the actions of allopurinol may be due to its inhibition of xanthine oxidase rather than a urate-lowering effect. This study also showed for the first time that a high dose (600 mg) is significantly better at improving endothelial function compared to standard doses.[11]
A recent study has suggested that allopurinol may help reduce the effects of angina in ischaemic heart disease by reducing the workload on the heart.[12]
Allopurinol is used as an add-on drug for refractory epilepsy, because it is an adenosine agonist, which inhibits glutamine release from excitatory neurons, but does not change the plasma concentration of other epilepsy drugs.[13]
Allopurinol can lower blood pressure in mild hypertension.[14]
A common misconception is that allopurinol is metabolized by its target, xanthine oxidase, but this action is principally carried out by Aldehyde oxidase.[15] The active metabolite of allopurinol is oxypurinol, which is also an inhibitor of xanthine oxidase. Allopurinol is almost completely metabolized to oxypurinol within two hours of oral administration, whereas oxypurinol is slowly excreted by the kidneys over 18–30 hours. For this reason, oxypurinol is believed responsible for the majority of allopurinol's effect.[16]
Because allopurinol is not a uricosuric, it can be used in patients with poor kidney function. However, allopurinol has two important disadvantages.
First, its dosing is complex,.[17] Second, some patients are hypersensitive to the drug,[18] therefore its use requires careful monitoring. Allopurinol has rare but potentially fatal adverse effects involving the skin. The most serious adverse effect is a hypersensitivity syndrome consisting of fever, skin rash, eosinophilia, hepatitis, worsened renal function, and, in some cases, allopurinol hypersensitivity syndrome.[18] Allopurinol is one of the drugs commonly known to cause Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TENS), two life-threatening dermatological conditions.[19] More common is a less-serious rash that leads to discontinuing this drug. Studies have found HLA-B*5801 allele as a genetic marker for severe cutaneous adverse reactions that include Steven Johnson Syndrome and toxic epidermal necrosis caused by allopurinol.[20]
More rarely, allopurinol can also result in the depression of bone marrow elements, leading to cytopenias, as well as aplastic anemia. Moreover, allopurinol can also cause peripheral neuritis in some patients, although this is a rare side effect. Another side effect of allopurinol is interstitial nephritis.[21]
It is suspected to cause congenital malformations when used during pregnancy, and should be avoided whenever possible by women trying to conceive.[22]
Allopurinol has been marketed in the United States since August 19, 1966, when it was first approved by FDA under the trade name of Zyloprim.[23] Allopurinol was marketed at the time by Burroughs-Wellcome. Allopurinol is now a generic drug sold under a variety of brand names including Allohexal, Allosig, Milurit, Alloril, Progout, Zyloprim, Zyloric, Zyrik and Aluron.[24]
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Ending of the drug name | Category | Example |
~afil | Erectile dysfunction | sildenafil |
~ane | Inhalatinal general anesthetic | halothane |
~azepam | Benzodiaizepine | diazepam |
~azine | Phenothiazine (neuroleptic, antiemetic) | chlorpromazine |
~azole | Ailtifungal | ketoconazole |
~barbital | Barbiturate | phenobarbital |
~caine | Local anesthetic | lidocaine |
~cillin | Penicillin | methicillin |
~cycline | Antibiotic, protein syntlesis inhibitor | tetracycline |
~ipramine | TCA | iimipramine |
~navir | Protease inhibitor | saquinavir |
~olol | β-antagonist | propranolol |
~operidol | Butyrophenone ( neuroleptic ) | haloperidol |
~oxin | Cardiac glycoside ( inotropic agent ) | digoxin |
~phylline | Methylxanthine | theophylline |
~pril | ACE inhibitor | captopril |
~terol | β2 agonist | albuterol |
~tidine | H2 antagonist | cimtidine |
~triptyline | TCA | amitriptyline |
~tropine | Pituitary hormone | somatotropine |
~zosin | a1 antagonist | prazosin |
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