Chapter 36 Nonsteroidal Anti-Inflammatory Drugs

Transcription

1 Chapter 36 Nonsteroidal Anti-Inflammatory Drugs

2 THERAPEUTIC STRATEGIES The treatment of patients with inflammation involves two primary goals: To relieve pain, To slow or arrest the tissue damaging process.

3 Glucocorticoids nonsteroidal anti inflmmatory drugs(nsaids) Analgesic antipyretic and anti inflammatory drugs: The NSAIDs continue to have a significant role in the long term treatment of arthritis.

4 Chemically heterogeneous agents, Aspirin is the prototype, so these compounds are often referred to as aspirin-like drugs. NSAIDS,share certain therapeutic actions. oaspirin osalsalate (Amigesic) odiflunisal (Dolobid) oibuprofen (Motrin 美林 ) oketoprofen (Orudis) onabumetone (Relafen) opiroxicam (Feldene) onaproxen 萘普生 (Naprosyn) odiclofenac (Voltaren) oindomethacin (Indocin) osulindac (Clinoril) otolmetin (Tolectin oetodolac (Lodine) oketorolac (Toradol) ooxaprozin (Daypro) ocelecoxib (Celebrex)

5 History of aspirin(acetylsalicylic acid) The origins of aspirin date back over 3500 years, to ease the pain of rheumatism and for back problems. In 1853,A French chemist, Charles Frederic Gerhardt In 1897, Felix Hoffman, Bayer Bayer registered Aspirin as a trademark and began selling it in Aspirin: A from acetyl chloride, the SPIR from the plant Spirae ulmaria. Aspirin is already a wonder drug. 1899: 1977: stoke, 2007, cancer

6 Oct 11, the Nobel Prize in Physiology or Medicine. for discovering the role of aspirin in inhibiting prostaglandin production Sune K. Bergström Prostaglandins are formed from unsaturated fatty acids Bengt I. Samuelsson arachidonic acid and prostaglandin metabolism John R. Vane He made the fundamental discovery that antiinflammatory compounds such as aspirin act by blocking the formation of prostaglandins and thromboxanes.

7 In 100 years, an estimated one trillion tablets having been consumed since its introduction. The twentieth century was dubbed the age of aspirin' by Spanish philosopher Jose Ortegay Gasset.

8 PHARMACOLOGICAL EFFECTS 1 Analgesic Action: Aspirin is most effective in reducing pain of mild to moderate intensity. PG(esp.PGE2) probably lowering the threshold of polymodal nociceptors ( 疼痛感受器 )

9 2 Antipyretic Action: Aspirin reduces elevated temperature, whereas normal body temperature is only slightly affected. The fall in temperature is related to 1) increases dissipation of heat caused by vasodilation of superficial blood vessels 2) by profuse sweating.

10 3. Anti-inflammatory Actions: Acute inflammation: initial response, autacoids(serotonin, leukotrienes, histamine) Immune response: beneficial: phagocytosed or neutralized deleterious: Chronic inflammation: release interleukin(il 1,2,3), TNF,

11 The Sites of NSAIDS Activity CELL MEMBRANE PHOSPHOLIPD Arachidonic acid lipoxygenase NSAID -- COX(cyclooxygenase) PGI2 gastric mucosa, platelets, endothelium PGH TXA2 Leukotriene PGD2 PGE2 gastric mucosa, kidney, periphral nociceptor PGF Chemotactic effects on neutrophils, macrophages, promote bronchoconstriction and alterations in vascular permeability

12 cyclooxygenase Cox 1: constitutively in most normal cells and tissues Cox 2: constitutive in brain, spinal cord and kidney and induced in response to inflammatory stimuli. Both enzymes produce prostaglandins that promote inflammation, pain, and fever. Only Cox 1 support platelets and protect the stomach. The more an NSAID blocks Cox 1, the greater is its tendency to cause ulcers and promote bleeding.

13 4.Effect on platlet Aspirin irreversibly inhibits platelet COX, thromboxanea2,txa2 so that aspirin's antiplatelet effect lasts 8 10 days (the life of the platelet).

14 Low dose Aspirine High dose antagonism Inhibite PG synthesizase PGI 2 Arachidonic acid COX platelets thromboxanea2,txa 2 Platelets aggregation PGI2: A vasodilator, anti-aggregate TXA2: A vasoconstrictor and causes platlet aggrgation

15 Pharmacokinetics A rise in ph increase the dissolution of the tablet, and aspirin is more ionized, accelerate absorption ; 80~90% bound to plasma proteins once absorbed, aspirin is rapidly converted to salicylic acid. Hepatic endoplasmic reticulum and mitochondria. Metabolites and some free salicylic acid are excreted in urine.

16 Pharmacological properties and therapeutic applications 1.Analgesia,Antipyresis and antiinflammatory effects relieves the most kinds of pain, esp. headache, myalgia and arthralgia(joint pain) Rheumatoid arthritis, rheumatic fever and other inflammatory joint conditions.

17 2. Potential Applications for Aspirin Heart attacks (and their prevention) Strokes Dementia (including Alzheimer s Disease) Aspirin is a unique NSAID, not only because of its many uses, but because it is the only NSAID that is able to inhibit the clotting of blood for a prolonged period (4 to 7 days). This prolonged effect of aspirin makes it an ideal drug for preventing the blood clots that cause heart attacks and strokes.

18 Adverse reactions 1 Gastrointestinal tract the most common adverse effects, such as epigastric distress, nausea, vomiting The gastric injury effects is related to the inhibition f PGs, such as PGI 1,PGE 2. Cox 1 is responsible for the serious gastrointestinal complications induced by NSAIDS in humans.

19 Ulcers and gastrointestinal bleeding This is the major danger with long-term use of NSAIDs and accounts for between 6,000 and 16,500 deaths, as well as 107,000 hospital admissions per year in the United States (and there are usually no warning symptoms before bleeding begins) For the average patient with rheumatoid arthritis, the chance of hospitalization or death due to a GI event (from NSAID use) is about 1.3 to 1.6% each 12 months, and about 1 in 3 over the entire course of the disease.

20 2 bleeding Increase bleeding time, decrease platelet adhesiveness, and may cause hypoprothrombinaemia With irreversible inhibitation of platelet COX, aspirin s antiplatelet effects will lasts 8 10 days. Stopped 1 week prior to surgery to avoid bleeding complications.

21 3.Hypersensitivity Rhinitis, angioneurotic edema, urticaria, bronchial asthma, diarrhea 4. Salicylism [sæli si lizəm] With higher dose, vomiting, tinnitus [tɪ naɪtəs] 耳鸣, decreased hearing, and vertigo 眩晕. Reversible by reducing dosage.

22 5. Hepatoxicity 6. Reye s syndrome Rare but often fatal syndrome characterised by fulminating hepatitis and cerebral edema in children. Children and teenagers should not use aspirin in viral infections. Acetaminophen is probably safer and equally effective, in place of aspirin

23 overdose Gastric lavage Alkalinize the urine with sodium bicarbonate infusions, to increase the amount of salicylate excreted 85% salicylate could be excrete in alkalide urine,whereas 5% in acid urine

24 Drug interactions NSAIDs reduce blood flow to the kidneys and therefore reduce the action of diuretics and decrease the elimination of lithium and methotrexate

25 Para-aminophenol derivatives(acetaminophen) Phenacetin 非那西丁 metabolism acetaminophen Paracetamol 扑热息痛, 对乙酰氨基酚

26 phenacetin sulfate acetaminophen Glucuronic acid salt Toxic metabolites Metabolism of Phenacetin in Body

27 Comparison between Aspirin and acetaminophen Effective analgesia and antipyretic effects as well as aspirin No effects on platelets and thus does not prolong the bleeding time; little anti inflammation; Overdose(10 15g)can result in severe liver damage and acute renal necrosis

28 Acetaminophen (Tylenol) overdose is the leading cause for calls to Poison Control Centers (>100,000/year) and accounts for more than 56,000 emergency room visits, 2,600 hospitalizations, and an estimated 458 deaths due to acute liver failure each year.

29 NSAIDs vary in their potency, duration of action, and the way in which they are eliminated from the body. Another important difference is their ability to cause ulcers and promote bleeding. The more an NSAID blocks Cox-1, the greater is its tendency to cause ulcers and promote bleeding

30 Indoleacetic acids Indomethacin 吲哚美辛, 消炎痛 Introduced in1963 Potent and nonselective COX inhibitor, may also inhibit PLC and PLA For use in rheumatic conditions and for gout(high uric acid) and ankylosing spondylitis 脊椎炎 Gastrointestinal effects,headache

31 Ibuprofen 布洛芬, 美林 Strong anti inflammation, analgesia and antipyretic effect High dose in cleft of joint, could be used in treatment of rheumatoid arthritis Less frequently in gastric toxicity and bleeding than aspirin;

32 naproxen 萘普生 Nonselective COX inhibitors Samilar with ibuprofen; Long half life (t 1/2 12~15h,while ibuprofen is 2h) The incidence of upper gastrointestinal bleeding is double that of ibuprofen

33 selective Cox-2 inhibitors Piroxicam 吡罗昔康, meloxicam 美洛昔康 : Strong inhibition of PG synthesis Good effective and less adverse reaction T 1/2 36~45h, Celecoxib 塞来考昔 : causes less bleeding and fewer ulcers than Aspirin. Nimesulide 尼美舒利 :used as anti inflamatory agents, Strong anti inflammation, Less gastric toxicity