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Chapter 10 Diuretics and Synthetic Hypoglycemic Drugs

Chapter 10 Diuretics and Synthetic Hypoglycemic Drugs. Pei Yu College of pharmacy Jinan University. Synthetic Hypoglycemic Agents ( 降血糖药 ). Definitions

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Chapter 10 Diuretics and Synthetic Hypoglycemic Drugs

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  1. Chapter 10 Diuretics and Synthetic Hypoglycemic Drugs Pei Yu College of pharmacy Jinan University

  2. Synthetic Hypoglycemic Agents(降血糖药) Definitions A key indicator of diabetes is persistent fasting blood glucose levels above 11.1 mmol/L which arise from defective conversion of glucose into energy. The plasma levels of FPG≥7.0mmol/L or PPG ≥11.1mmol/L

  3. Diabetes • Hyperglycemia result in widespread damage in the body that can lead to hypertension, heart disease, stroke, impaired circulation, nerve dysfunction, pain, infection, or organ failure. • Clinical diabetes mellitus（糖尿病）occurs in two forms, Type 1 and Type 2, with different causes and methods of therapy.

  4. Type 1 Diabetes (insulin-dependent) • Formerly known as insulin-dependent diabetes mellitus (IDDM, 胰岛素依赖性糖尿病). • The β–cells of the pancreatic islets of Langerhans (胰岛) are destroyed, probably by an autoimmune process, such that insulin production is grossly deficient（严重缺乏）. • There exists only a weak genetic link in the etiology(病原学)of this form of diabetes. • Type 1 diabetes is invariably treated with insulin.

  5. Type 2 Diabetes (noninsulin-dependent) • Formerly known as noninsulin-dependent diabetes mellitus (NIDDM). • Frequently associated with obesity(肥胖症)in its mainly adult victims. Serum insulin levels are normal or elevated, so in essence this is a disease of insulin resistance. • There is a strong genetic link in the etiology（病原学）of the condition, and insulin therapy is not always required.

  6. Hypoglycemic Drugs Treatments of Type 2 diabetes include： (1) agents which increase the amount of insulin secreted by the pancreas (2) agents which increase the sensitivity of target organs to insulin (3) agents which decrease the rate at which glucose is absorbed from the gastrointestinal tract.

  7. Classification of Hypoglycemic Drug • Sulfonylureas (磺酰脲类) • Biguanides (双胍类) • α-Glucosidase inhibitors (α-葡萄糖苷酶抑制剂) • Thiazolindiones (噻唑烷二酮类)

  8. Sulfonylureas(磺酰脲类) • The hypoglycemic(降血糖)effect of salicylates(水杨酸盐)has been known for 100 years. Clinical use of salicylates was not feasible, since the very large doses required produced intolerable side effects. • The hypoglycemic effects of the thiadiazole sulfonamide known as IPTD, used to treat typhoid (伤寒症)fever in the 1940s. This drug produced many deaths which were subsequently attributed to prolonged drug-induced hypoglycemia.

  9. Sulfonylureas • At same time these effects were noted, the synthesis of sulfonylurea such as Carbutamide, so far active as hypoglycemic agents, was reported. • Since then, about 12, 000 sulfonylureas have been tested, and about 10 are currently on the market.

  10. Sulfonylureas • Tolbutamide 甲苯磺丁脲 • Chlorpropamide 氯磺丙脲 • Acetohexamide 醋磺己脲 • Tolazamide 妥拉磺脲 • Gliclazide 格列齐特 • Glibornuride 格列波脲 • Glibenclamide 格列本脲 • Glipizide 格列吡嗪 • Gliquidone 格列喹酮 • Glimepiride 格列美脲 1st generation 2nd generation 3rd generation

  11. First and second generation sulfonylureas

  12. Tolbutamide (甲苯磺丁脲 ) 1-Butyl-3-(p-tolylsulfonyl)urea N-[(butylamino)carbonyl]-4-methylbenzenesulfonamide White, crystalline powder, insoluble in water, soluble in alcohol or aqueous alkali. It is stable in air.

  13. Acidic property Tolbutamide shows acidic property，it can be dissolved in base.

  14. Unstable under acidic condition. odour

  15. Metabolism of Tolbutamide • Tolbutamide is absorbed rapidly in responsive diabetic patients. The blood sugar level reaches a minimum after 5-8 h. • It is oxidized rapidly in vivo to derivative with hydroxyl group (I) or derivative with carboxyl group (II), which are inactive.

  16. Synthesis of Tolbutamide

  17. Glibenclamide(格列本脲 ) 1-[[p-[2-(5-chloro-o-anisamido)ethyl]-phenyl]sulfonyl] -3-cyclohexylurea. • Second-generation oral hypoglycemic agent. • The drug has a half-life elimination of 10h, but its hypoglycemic effect remains for up to 24h.

  18. Hydrolysis of Glibenclamide

  19. Glimepiride(格列美脲) 1-[[p-[2-(3-ethyl-4-methyl-2-oxo-3-pyrroline-1-carboxamido)ethyl] phenyl]sulfonyl]-3-(trans-4-methylcyclohexyl)urea. • The third-generation oral hypoglycemic agent. • Instead of the benzene ring found in Glibenclamide, Glimepiride contains a pyrrolidine system. • It is metabolized primarily through oxidation of the alkyl side chain of the pyrrolidine, with a minor metabolic route involving acetylation of the amine.

  20. Other Antidiabetic drugs: • Biguanide:(双胍) • The most commonly used oral drug for type 2 diabetes. • Increasing insulin sensitivity. • Decreasing the absorption of glucose from the gastroinestinal tract.

  21. Discovery • The guanidine derivatives（胍衍生物）Synthalin A and B were introduced into therapy in the 1920s, but chronic toxicity forced their abandonment in the 1930s. • The widely used biguanides(双胍) Phenformin and Metformin were prepared in the 1950s, and the latter is still in widespread use.

  22. Metformin Hydrochloride（盐酸二甲双胍） N，N-Dimethylimidodicarbonimidic diamide hydrochloride

  23. Metformin • Metformin was discovered in 1957，it was not approved by the FDA until 1994 for the treatment of type 2 diabetes. • It is to lower blood glucose and to reduce cardiovascular complications（并发症）. • Over 6 million people were treated by it annually.

  24. α-Glucosidase inhibitorsMiglitol (米格列醇) 1-(2-Hydroxyethyl)-2-(hydroxymethyl)piperidine-3,4,5-triol pyranose

  25. Miglitol • White to pale-yellow powder is soluble in water, and exhibits a pKa 5.9. • In chemical structure, this agent is very simliar to a pyranose sugar(吡喃糖), with a nitrogen atom replacing the oxygen isosterically. • α-Glucosidase takes it in as a substrate and is thereby competitively inhibited. • The end result is a delay in the absorption of complex carbohydrates from the gastrointestinal tract.

  26. Thiazolindiones(噻唑烷二酮类)Rosiglitazone Maleate (马来酸罗格列酮) Chemical Name: (5-[[4-[2-methyl-2-pyridinylamino)ethoxy]phenyl]methyl] -2,4-thiazolidinedione maleate

  27. Avandia 文迪雅 Function of Rosiglitazone Maleate • Rosiglitazone maleate is not chemically or functionally related to the sulfonylureas, the biguanides, or the alpha-glucosidase inhibitors. • It is an oral antidiabetic agent which acts primarily by increasing insulin sensitivity. • It sales 3.6-3.8 billion USD in 2008.

  28. Side Effects • It is reported in May 2007 that the use of rosiglitazone was associated with a significantly increased risk of heart attack, and an even higher risk of death from all cardiovascular diseases. • The FDA issued an alert on May 21, 2007. • In 2009 the study found that there was no increase in cardiovascular hospitalisation or death with rosiglitazone compared to metformin plus sulfonylurea, but the rate of heart failure causing admission to hospital or death was significantly increased.

  29. Diuretics(利尿剂) Definition: Diuretics are drugs that increase the rate of urine formation. More commonly known as “water pills”. Some people use diuretics as a weight loss aid. This is not a healthy way to lose weight. Abusing diuretics can lead to dehydration and sometimes severe potassium deficiencies.

  30. Diuretics increase the rate of urine formation by interfering with the re-absorption of sodium by the nephron(肾元). • There are four major anatomical(解剖)sites along the nephron that are responsible for the bulk of Na+ re-absorption.

  31. Sodium Reabsorption Sites in the Nephron 65% 5% Proximal Tubule近端小管 Distal Tubule远端小管 1 3 Collecting Tubule集合小管 Glomerulus肾小球 2 30% 4 1-4% Loop of Helen细尿管袢

  32. Four major anatomical(解剖学)sites • Site 1: the convoluted and straight portions of the proximal tubule(近端小管); • Site 2: the thick ascending limb(升支)of Helen’s loop; • Site 3: the distal convoluted tubule(远曲小管); • Site 4: the connecting tubule(集合小管) and the cortical collecting tubule(皮质部集合小管).

  33. Triamterene hydrochlorothiazide acetazolamide acetazolamide 3 1 furosemide 2 4 Spironolactone sfuf fu

  34. Potency and efficacy of Diuretics Diuretic efficacy has increased with the corresponding changes in the site of action of each of three classes of diuretics: Class 1, CA inhibitor: Inhibit the reabsorption of Na+/HCO3-at site 1. Weaker Class 2, Thiazide and thiazide-like diuretics: Inhibit the reabsorption of Na+/Cl- at site 3. Stronger Class 3, High-ceiling diuretics: Block Na+/Cl-/K+/Ca+/Mg2+ reabsorption at site 2.

  35. Class 1: Carbonic Anhydrase Inhibitors • Shortly after its introduction for the treatment of bacterial infections, sulfanilamide was observed to produce a mild diuresis characterized by presence of urinary Na+ and a substantial amount of HCO3-. • It induced this effect through inhibition of renal carbonic anhydrase (碳酸酐酶，CA). • It was a relatively weak inhibitor of renal CA, and the dose needed to exert adequate diuresis was associated with severe adverse effects.

  36. CA inhibitor • To improve on the CA-inhibitory property of sulfanilamide, many sulfamoyl-containing compounds (-SO2NH2) were synthesized. • Two groups of CA inhibitors emerged: simple heterocyclic sulfonamides and meta- disulfamoylbenzene derivatives.

  37. Two groups of CA inhibitors

  38. Common CA inhibitor

  39. Acetazolamide • Name:（Diamox) N-[5-(aminosulfony)-1,3,4-thiadiazol-2-yl]acetamide. • White needle crystal, m.p. 258-259 ºC, soluble in basic solution (NH3.H2O).

  40. Acetazolamide • It was introduced in 1953 as the first orally effective, non-mercurial diuretic available to the physician. • It has a relatively restricted use today because of its limited efficacy and the refractoriness (失效) that develops to its diuretic action within the first week of continuous therapy.

  41. Mechanism of action Similar structure

  42. Uses • The major use of the CA inhibitors is in the treatment of glaucoma (青光眼). • CA is a functionally important enzyme in the eye, where it plays a key role in the formation of aqueous humor (眼球的水状体). • As adjuvants(佐药)for the treatment of epilepsy(癫痫). • Create an alkaline urine in an attempt to hasten the renal excretion of certain noxious weak acids (uric acid). • CA inhibitors have been used prophylactically(预防) to counteract (抵抗)acute mountain sickness(急性高山病). 急性高山反应：由于在高海拔人呼吸急促，血液里氧气不足导致了碳酸过多，碳酸过多引起轻微脑部水肿，结果是头疼和心。

  43. Class 2: Thiazide and Thiazide-like diuretics

  44. Chloraminophenamide became a key intermediate in the development of diuretics that lack the undesirable properties of the CA inhibitors (???). • When Chloraminophenamide was treated with acylating agents, cyclization resulted in the formation of Thiazides. The use of aldehydes or ketones in place of the acylating reagents yielded the corresponding dihydro derivatives. The products of these reactions became known as thiazidesandhydrothiazides, respectively. • The thiazides were the first orally effective saluretic agents（促尿食盐排泄药）whose diuretic activity was not influenced by the patient’s acid-base status.

  45. Hydrochlorothiazide • Name：6-Chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide,1,1-dioxide • It can be hydrolyzed in water.

  46. Synthesis of Hydrochlorothiazide

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