Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biguanide metformin (dimethylbiguanide) is an oral antihyperglycaemic agent widely used in the management of non-insulin-dependent diabetes mellitus (NIDDM). Considerable renewal of interest in this drug has been observed in recent years. Metformin can be determined in biological fluids by various methods, mainly using high performance liquid chromatography, which allows pharmacokinetic studies in healthy volunteers and diabetic patients. Metformin disposition is apparently unaffected by the presence of diabetes and only slightly affected by the use of different oral formulations. Metformin has an absolute oral bioavailability of 40 to 60%, and gastrointestinal absorption is apparently complete within 6 hours of ingestion. An inverse relationship was observed between the dose ingested and the relative absorption with therapeutic doses ranging from 0.5 to 1.5 g, suggesting the involvement of an active, saturable absorption process. Metformin is rapidly distributed following absorption and does not bind to plasma proteins. No metabolites or conjugates of metformin have been identified. The absence of liver metabolism clearly differentiates the pharmacokinetics of metformin from that of other biguanides, such as phenformin. Metformin undergoes renal excretion and has a mean plasma elimination half-life after oral administration of between 4.0 and 8.7 hours. This elimination is prolonged in patients with renal impairment and correlates with creatinine clearance. There are only scarce data on the relationship between plasma metformin concentrations and metabolic effects. Therapeutic levels may be 0.5 to 1.0 mg/L in the fasting state and 1 to 2 mg/L after a meal, but monitoring has little clinical value except when lactic acidosis is suspected or present. Indeed, when lactic acidosis occurs in metformin-treated patients, early determination of the metformin plasma concentration appears to be the best criterion for assessing the involvement of the drug in this acute condition. After confirmation of the diagnosis, treatment should rapidly involve forced diuresis or haemodialysis, both of which favour rapid elimination of the drug. Although serious, lactic acidosis due to metformin is rare and may be minimised by strict adherence to prescribing guidelines and contraindications, particularly the presence of renal failure. Finally, only very few drug interactions have been described with metformin in healthy volunteers. Plasma levels may be reduced by guar gum and alpha-glucosidase inhibitors and increased by cimetidine, but no data are yet available in the diabetic population.
 ...
PMID:Clinical pharmacokinetics of metformin. 874 35

Type 2 diabetes mellitus (formerly named non-insulin-dependent diabetes mellitus or NIDDM) is a heterogeneous disease resulting from a dynamic interaction between defects in insulin secretion and insulin action. Various pharmacological approaches can be used to improve glucose homeostasis via different modes of action: sulphonylureas essentially stimulate insulin secretion, biguanides (metformin) act by promoting glucose utilisation and reducing hepatic-glucose production, alpha-glucosidase inhibitors (acarbose) slow down carbohydrate absorption from the gut and thiazolidinediones (troglitazone) enhance cellular insulin action on glucose and lipid metabolism. These pharmacological treatments may be used individually for certain types of patients, or may be combined in a stepwise fashion to provide more ideal glycaemic control for most patients. Selection of oral antihyperglycaemic agents as first-line drug or combined therapy should be based on both the pharmacological properties of the compounds (efficacy and safety, profile) and the clinical characteristics of the patient (stage of disease, bodyweight, etc.). Mildly hyperglycaemic patients should preferably be treated with metformin, acarbose or thiazolidinediones (which are not associated with any hypoglycaemic risk), while more severely hyperglycaemic individuals should receive a sulphonylurea. In moderately hyperglycaemic patients, sulphonylureas should be preferred in nonobese patients while metformin, and probably also thiazolidinediones, should have priority in obese insulin-resistant type 2 diabetic patients. Acarbose is mainly indicated to reduce post-prandial glucose fluctuations and improve glycaemic stability. Each antihyperglycaemic agent may also be combined with insulin therapy to improve glycaemic control and/or reduce the insulin requirement of diabetic patients after secondary failure to oral treatment. Finally, safety should be taken into account in elderly patients and/or those with renal impairment, especially as far as the use of sulphonylureas (higher risk of hypoglycaemia) and metformin (higher risk of lactic acidosis) is concerned.
 ...
PMID:Oral antidiabetic agents. A guide to selection. 950 42

Type 2 diabetes mellitus is a progressive and complex disorder that is difficult to treat effectively in the long term. The majority of patients are overweight or obese at diagnosis and will be unable to achieve or sustain near normoglycaemia without oral antidiabetic agents; a sizeable proportion of patients will eventually require insulin therapy to maintain long-term glycaemic control, either as monotherapy or in conjunction with oral antidiabetic therapy. The frequent need for escalating therapy is held to reflect progressive loss of islet beta-cell function, usually in the presence of obesity-related insulin resistance. Today's clinicians are presented with an extensive range of oral antidiabetic drugs for type 2 diabetes. The main classes are heterogeneous in their modes of action, safety profiles and tolerability. These main classes include agents that stimulate insulin secretion (sulphonylureas and rapid-acting secretagogues), reduce hepatic glucose production (biguanides), delay digestion and absorption of intestinal carbohydrate (alpha-glucosidase inhibitors) or improve insulin action (thiazolidinediones). The UKPDS (United Kingdom Prospective Diabetes Study) demonstrated the benefits of intensified glycaemic control on microvascular complications in newly diagnosed patients with type 2 diabetes. However, the picture was less clearcut with regard to macrovascular disease, with neither sulphonylureas nor insulin significantly reducing cardiovascular events. The impact of oral antidiabetic agents on atherosclerosis--beyond expected effects on glycaemic control--is an increasingly important consideration. In the UKPDS, overweight and obese patients randomised to initial monotherapy with metformin experienced significant reductions in myocardial infarction and diabetes-related deaths. Metformin does not promote weight gain and has beneficial effects on several cardiovascular risk factors. Accordingly, metformin is widely regarded as the drug of choice for most patients with type 2 diabetes. Concern about cardiovascular safety of sulphonylureas has largely dissipated with generally reassuring results from clinical trials, including the UKPDS. Encouragingly, the recent Steno-2 Study showed that intensive target-driven, multifactorial approach to management, based around a sulphonylurea, reduced the risk of both micro- and macrovascular complications in high-risk patients. Theoretical advantages of selectively targeting postprandial hyperglycaemia require confirmation in clinical trials of drugs with preferential effects on this facet of hyperglycaemia are currently in progress. The insulin-sensitising thiazolidinedione class of antidiabetic agents has potentially advantageous effects on multiple components of the metabolic syndrome; the results of clinical trials with cardiovascular endpoints are awaited. The selection of initial monotherapy is based on a clinical and biochemical assessment of the patient, safety considerations being paramount. In some circumstances, for example pregnancy or severe hepatic or renal impairment, insulin may be the treatment of choice when nonpharmacological measures prove inadequate. Insulin is also required for metabolic decompensation, that is, incipient or actual diabetic ketoacidosis, or non-ketotic hyperosmolar hyperglycaemia. Certain comorbidities, for example presentation with myocardial infarction during other acute intercurrent illness, may make insulin the best option. Oral antidiabetic agents should be initiated at a low dose and titrated up according to glycaemic response, as judged by measurement of glycosylated haemoglobin (HbA1c) concentration, supplemented in some patients by self monitoring of capillary blood glucose. The average glucose-lowering effect of the major classes of oral antidiabetic agents is broadly similar (averaging a 1-2% reduction in HbA1c), alpha-glucosidase inhibitors being rather less effective. Tailoring the treatment to the individual patient is an important principle. Doses are gradually titrated up according to response. However, the maximal glucose-lowering action for sulphonylureas is usually attained at appreciably lower doses (approximately 50%) than the manufacturers' recommended daily maximum. Combinations of certain agents, for example a secretagogue plus a biguanide or a thiazolidinedione, are logical and widely used, and combination preparations are now available in some countries. While the benefits of metformin added to a sulphonylurea were initially less favourable in the UKPDS, longer-term data have allayed concern. When considering long-term therapy, issues such as tolerability and convenience are important additional considerations. Neither sulphonylureas nor biguanides are able to appreciably alter the rate of progression of hyperglycaemia in patients with type 2 diabetes. Preliminary data suggesting that thiazolidinediones may provide better long-term glycaemic stability are currently being tested in clinical trials; current evidence, while encouraging, is not conclusive. Delayed progression from glucose intolerance to type 2 diabetes in high-risk individuals with glucose intolerance has been demonstrated with troglitazone, metformin and acarbose. However, intensive lifestyle intervention can be more effective than drug therapy, at least in the setting of interventional clinical trials. No antidiabetic drugs are presently licensed for use in prediabetic individuals.
 ...
PMID:Oral antidiabetic agents: current role in type 2 diabetes mellitus. 1566 80