40 Questions
What is the primary use of opioids in medical practice?
Relieving chronic pain symptoms
What is the significance of Serturner's discovery of morphine in 1803?
It introduced the term 'analgesia' into medical literature
What is the main difference between analgesics and anesthetics?
Analgesics relieve pain without causing loss of consciousness, while anesthetics produce insensivity to pain with loss of consciousness
Which of the following opioids is used as an anti-diarrheal agent?
Loperamide
What is the primary site of action for analgesics?
Cerebrum and medulla
Which of the following is a centrally acting non-narcotic analgesic?
D-Proxyphene
What is the purpose of methadone and buprenorphine in opioid therapy?
To counter addiction to more potent opioids
What is the significance of the discovery of ether by Sir Humphrey Davy and others in the 19th century?
It introduced the concept of anesthesia into medicine
What is the percentage of morphine in dried opium?
10%
What is the name of the ring system found in the morphine group of opium alkaloids?
Phenanthrene
Which of the following is a synthetic opioid?
Fentanyl
What is the name of the opioid that is classified under the 4-Phenylpiperidines group?
Loperamide
Which of the following is an example of an endogenous opioid?
Endorphin
What is the percentage of papaverine in dried opium?
1%
Which of the following is a semi-synthetic opioid?
Buprenorphine
What is the name of the ring system found in the papaverine group of opium alkaloids?
Isoquinoline
Who achieved the total synthesis of morphine in 1952?
Gates and Tschud
What is the effect of changing the –OH group to –H or –OCH3 in the phenolic ring of morphine?
Decrease in activity
What is the minimum number of carbon atoms required for antagonist activity in a substituent on the nitrogen atom of morphine?
3 carbon
What is the effect of removing other rings from the structure of morphine?
No effect on activity
What is the property of morphine that limits its clinical use?
High dependence liability
What is the characteristic of the (+) isomer of morphine?
It has no analgesic activity
What is the number of chiral centers present in morphine?
5
What is the preferred form of morphine used in clinical practice?
Both b and c
What is the primary characteristic of neuropathic pain?
It is characterized by shooting, burning, tingling, or electric shock-like sensations
Which type of pain occurs when a nerve root is compressed or irritated?
Radicular pain
What is the primary cause of psychogenic pain?
Emotional distress, depression, anxiety, or somatization disorders
Which type of pain relief blocks the local pain messenger such as prostaglandin?
Non- Steroidal Anti- Inflammatory Drugs (NSAIDs)
What is the primary difference between General Anaesthetics (GA) and General Anaesthetics (LA)?
GA affects the chemical component of neuro transmission, while LA affects the electrical component
What is the primary characteristic of phantom pain?
It occurs after the amputation or removal of a body part
Which type of pain relief blocks both chemical and electrical components of nerve transmission?
Opioids
What is the primary characteristic of referred pain?
It is felt in a location different from the actual source of the problem
What is the effect of including a double bond or a small carbo-cyclic ring in the R group on the mu antagonist effect?
Increases the mu antagonist effect
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?
Increases the mu agonist effect
What is the effect of reducing the 7,8 double bond on the activity of the compound?
Increases the activity
What is the effect of including a hydroxyl group at the 14 position on the activity of the compound?
Increases the activity
What is the effect of removing the hydroxyl group at the 6 position on the activity of the compound?
Increases the activity
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?
Increases the activity
What is the effect of acetylating the hydroxyl group at the 6 position on the activity of the compound?
Increases the activity
What is the effect of removing the ether linkage on the activity of the compound?
Increases the activity
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
Learn about the different types of pain, including neuropathic pain and radicular pain, their causes and characteristics.
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