Medicinal Chemistry: Types of Pain
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Questions and Answers

What is the primary use of opioids in medical practice?

  • Preventing diarrhea and cough
  • Treating opioid addiction
  • Relieving chronic pain symptoms (correct)
  • Inducing anesthesia in patients

    • What is the significance of Serturner's discovery of morphine in 1803?

  • It introduced the term 'analgesia' into medical literature (correct)
  • It introduced the concept of anesthesia into medicine
  • It led to the development of new analgesic agents
  • It marked the beginning of pain relief research

    • What is the main difference between analgesics and anesthetics?

  • Analgesics are used for children, while anesthetics are used for adults
  • Analgesics are used for cancer pain, while anesthetics are used for postoperative pain
  • Analgesics relieve pain without causing loss of consciousness, while anesthetics produce insensivity to pain with loss of consciousness (correct)
  • Analgesics are used for chronic pain, while anesthetics are used for surgery

    • Which of the following opioids is used as an anti-diarrheal agent?

    <p>Loperamide</p> Signup and view all the answers

    What is the primary site of action for analgesics?

    <p>Cerebrum and medulla</p> Signup and view all the answers

    Which of the following is a centrally acting non-narcotic analgesic?

    <p>D-Proxyphene</p> Signup and view all the answers

    What is the purpose of methadone and buprenorphine in opioid therapy?

    <p>To counter addiction to more potent opioids</p> Signup and view all the answers

    What is the significance of the discovery of ether by Sir Humphrey Davy and others in the 19th century?

    <p>It introduced the concept of anesthesia into medicine</p> Signup and view all the answers

    What is the percentage of morphine in dried opium?

    <p>10%</p> Signup and view all the answers

    What is the name of the ring system found in the morphine group of opium alkaloids?

    <p>Phenanthrene</p> Signup and view all the answers

    Which of the following is a synthetic opioid?

    <p>Fentanyl</p> Signup and view all the answers

    What is the name of the opioid that is classified under the 4-Phenylpiperidines group?

    <p>Loperamide</p> Signup and view all the answers

    Which of the following is an example of an endogenous opioid?

    <p>Endorphin</p> Signup and view all the answers

    What is the percentage of papaverine in dried opium?

    <p>1%</p> Signup and view all the answers

    Which of the following is a semi-synthetic opioid?

    <p>Buprenorphine</p> Signup and view all the answers

    What is the name of the ring system found in the papaverine group of opium alkaloids?

    <p>Isoquinoline</p> Signup and view all the answers

    Who achieved the total synthesis of morphine in 1952?

    <p>Gates and Tschud</p> Signup and view all the answers

    What is the effect of changing the –OH group to –H or –OCH3 in the phenolic ring of morphine?

    <p>Decrease in activity</p> Signup and view all the answers

    What is the minimum number of carbon atoms required for antagonist activity in a substituent on the nitrogen atom of morphine?

    <p>3 carbon</p> Signup and view all the answers

    What is the effect of removing other rings from the structure of morphine?

    <p>No effect on activity</p> Signup and view all the answers

    What is the property of morphine that limits its clinical use?

    <p>High dependence liability</p> Signup and view all the answers

    What is the characteristic of the (+) isomer of morphine?

    <p>It has no analgesic activity</p> Signup and view all the answers

    What is the number of chiral centers present in morphine?

    <p>5</p> Signup and view all the answers

    What is the preferred form of morphine used in clinical practice?

    <p>Both b and c</p> Signup and view all the answers

    What is the primary characteristic of neuropathic pain?

    <p>It is characterized by shooting, burning, tingling, or electric shock-like sensations</p> Signup and view all the answers

    Which type of pain occurs when a nerve root is compressed or irritated?

    <p>Radicular pain</p> Signup and view all the answers

    What is the primary cause of psychogenic pain?

    <p>Emotional distress, depression, anxiety, or somatization disorders</p> Signup and view all the answers

    Which type of pain relief blocks the local pain messenger such as prostaglandin?

    <p>Non- Steroidal Anti- Inflammatory Drugs (NSAIDs)</p> Signup and view all the answers

    What is the primary difference between General Anaesthetics (GA) and General Anaesthetics (LA)?

    <p>GA affects the chemical component of neuro transmission, while LA affects the electrical component</p> Signup and view all the answers

    What is the primary characteristic of phantom pain?

    <p>It occurs after the amputation or removal of a body part</p> Signup and view all the answers

    Which type of pain relief blocks both chemical and electrical components of nerve transmission?

    <p>Opioids</p> Signup and view all the answers

    What is the primary characteristic of referred pain?

    <p>It is felt in a location different from the actual source of the problem</p> Signup and view all the answers

    What is the effect of including a double bond or a small carbo-cyclic ring in the R group on the mu antagonist effect?

    <p>Increases the mu antagonist effect</p> Signup and view all the answers

    What is the effect of having a chain or ring with more than 5 carbon atoms in the R group on the mu agonist effect?

    <p>Increases the mu agonist effect</p> Signup and view all the answers

    What is the effect of reducing the 7,8 double bond on the activity of the compound?

    <p>Increases the activity</p> Signup and view all the answers

    What is the effect of including a hydroxyl group at the 14 position on the activity of the compound?

    <p>Increases the activity</p> Signup and view all the answers

    What is the effect of removing the hydroxyl group at the 6 position on the activity of the compound?

    <p>Increases the activity</p> Signup and view all the answers

    What is the effect of oxidizing the hydroxyl group at the 6 position to a keto group, with simultaneous reduction of the 7,8 double bond?

    <p>Increases the activity</p> Signup and view all the answers

    What is the effect of acetylating the hydroxyl group at the 6 position on the activity of the compound?

    <p>Increases the activity</p> Signup and view all the answers

    What is the effect of removing the ether linkage on the activity of the compound?

    <p>Increases the activity</p> Signup and view all the answers

    Study Notes

    Types of Pain

    • Neuropathic Pain: results from damage or dysfunction in the nervous system, characterized by shooting, burning, tingling, or electric shock-like sensations
    • Radicular Pain: occurs when a nerve root is compressed or irritated, leading to pain that radiates along the nerve's pathway
    • Referred Pain: felt in a location different from the actual source of the problem
    • Psychogenic Pain: has a psychological origin and is not associated with any physical damage or injury
    • Phantom Pain: occurs after the amputation or removal of a body part, where the person continues to experience pain in the absent limb

    Ways to Relieve Pain

    • General Anaesthetics (GA): affect the chemical component of neuro transmission (GABA and NMDA receptors)
    • General Anaesthetics (LA): block the electrical component of neuro transmission (Voltage Gated Na+ channel)
    • Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): block local pain messengers such as prostaglandin
    • Opioids: block both chemical and electrical components of nerve transmission, except for NSAIDs, all three are CNS depressants

    Opioids

    • Used for symptomatic relief of pain
    • Choice of drugs for managing chronic pain, such as cancer or rheumatoid arthritis
    • Used as inducing agents or analgesic supplements with general anesthetics
    • Have clinical use as anti-diarrheal and antitussive agents

    Analgesics

    • Definition: absence of sensibility to pain, physiologically due to a raising of the pain threshold
    • Analgesics are selective central nervous system (CNS) depressants, grouped into:
      • Centrally acting narcotics (e.g. morphine)
      • Peripherally acting non-narcotics (e.g. salicylates)
      • Centrally acting non-narcotics (e.g. d-propoxyphene)

    Opium

    • Greek word meaning "juice" or extract of seeds from the poppy Papaver somniferum
    • Contains over 20 distinct alkaloids, including morphine, codeine, narcotine, and papaverine

    Opioids Classification

    • Natural Opium Alkaloids: Morphine and Codeine
    • Semi-synthetic: Buprenorphine, Oxycodone, Diacetylmorphine (Heroin)
    • Synthetic opioids: 4-Phenylpiperidines, Diphenylpropylamine derivatives, Benzomorphans, and Morphismans
    • Endogenous opioids: Natural pain-relieving peptides of the body, such as endorphins, enkephalins, and dynorphins

    Structure-Activity Relationship (SAR)

    • Morphine has 5 chiral centers, with only the Levo (-) rotatory isomer being active
    • The OH group in the phenolic ring and basic Nitrogen are needed for activity
    • Modification to Morphine:
      • Changing -OH to -H or -OCH3 lowers activity
      • Loss of other rings does not affect analgesic activity
      • Increasing size of substituent on Nitrogen dictates potency and agonist or antagonist activity

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    Description

    Learn about the different types of pain, including neuropathic pain and radicular pain, their causes and characteristics.

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