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Introduction to Medicinal Chemistry Chapter 1 Part 1 What is medicinal chemistry? The science that deals with the discovery or design of new therapeutic chemicals and the development of these chemicals into useful medicine What is “medicine”? Drugs, pharmaceutics Media distinction A compound that interacts with a biological system, and produces a biological response (ideally desired and positive) “Good” vs. “Bad” Drugs No medicine has only benefits or drawbacks Morphine HO Excellent analgesic Addictive, tolerance Respiratory depression O N Barbiturates Depressants, sedatives, anesthetics Surgery Overdoses fatal (Pearl Harbor) H HO CH3 Heroin Known clinically as Diamorphine One of the best painkillers 1898: on market 1903: withdrawn (addictive properties) Today: still used H3C O C O O N O H C H3C O CH3 Aspirin 400 BC: Hippocrates Chew bark of willow tree for pain (childbirth and eye infections) Active component of willow bark = salicin O O OH glucose O O OH 1. Hydrolysis 2. Oxidation OH Ac2O Ac (1883: Bayer) OH Salisylic acid - more effective - no bitter taste - gastric bleeding O Acetylsalicylic acid (aspirin) - less irritating - ester hydrolyzes to active drug Cocaine O O South American coca bush Plant used as a stimulant, mystical/religious O O reasons N Isolated 1880’s Anesthetic in dentistry Addiction: Freud Used for depression; other drug addiction Drug development based on structure Procaine (Novocain) O N O NH2 Everyday drugs Still produce a response; many are addictive Caffeine Sugar Nicotine Alcohol Food additives Vitamins Herbs Basil: 50 potential carcinogens Cultural aspects “Good” vs. “Bad” Drugs Depends on: Dosage Almost anything in excess will be toxic Chronic exposure Measure of safety of drug = therapeutic index Therapeutic index Measure of a drug’s beneficial effects at low dose vs. harmful effects at high dose Comparison of dose levels which lead to toxic effects to dose levels which lead to maximum therapeutic effects High therapeutic index = large margin of safety Marijuana = 1000 Alcohol = 10 Does not take chronic use into account Classification of drugs Four main groups (overlap) 1. By pharmacological effects 2. Analgesics, anti-asthmatics, antipsychotics, etc. Large and varied assortment of drugs Many mechanisms of action By chemical structure Penicillins, steroids Common skeleton Functions may be similar or different Classification of drugs 3. By target system Antihistamines Affect a target system (synthesis, release, receptor) Variety of structures due to large number of stages in system 4. By target molecule or site of action on target Very specific classification Expect structural similarity and common mechanism Easy to classify compounds too narrowly and miss possible positive side effects (new uses for the compound) Zyban Viagra