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PROTOTYPE DRUGS AND THEIR DERIVATIVES - PART 1 (Morphine (Nalorphine,…
PROTOTYPE DRUGS AND THEIR DERIVATIVES - PART 1
Morphine
Heroin
(Diamorphine)
More potent than morphine
Used to be alternative to morphine as analegesia
Used to be codeine substitute for cough
Most addictive drug ever
Hydrochloride salt is very water-soluble
Apomorphine
Degradation product of morphine heated with concentrated HCl
Powerful emetic to treat poisoning
No analgesic effect
Control Parkinson's disease due to similar structure as dopamine
Metopon (methyldihydromorphinone)
Methylated derivative of hydromorphone. Structure of hydromorphone:
3x more potent than morphine in analgesia - less drowsiness and nausea
Production is expensive
Nalorphine
Potent antagonist of morphine due to presence of allyl group
Restore normal respiration among opium addicts who experienced respiratory depression
Produce non-addictive analgesia
Cause disturbing hallucinations among non-addicts
Reverse opium overdose
:star:
Cause respiratory depression among non-addicts
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Naloxone
Occupies morphine receptors - result in complete lack of agonist receptors
Safest anatgonist for opium overdose
:star: :star:
Levorphanol
Greater lipophilicity
- hence greater extensive distribution and longer duration of action
Reabsorption by the kidney delays excretion of drug
Longer elimination half-life than morphine
- less dosing
N-allyl analogue to produce
levallorphan
Antagonist for morphine
Used to reverse respiratory depression caused by opium during general anaesthesia
Dextrorotatory isomer of levorphanol -
dextrorphan
Methyl ether -
dextromethorphan
Antitussive
Phenazocine
3x more potent than morphine
Highly lipophilic -
well-absorbed from GI
Tablet is given for controlling severe pain
Pentazocine
Only 1/3 potency of morphine when injected
Low addictive liability due to similar structure to codeine
Induce hallucination
For moderate pain
Codeine
(methylmorphine)
Prodrug
-metabolised into active form as morphine
Can cause respiratory depression
Antitussive
Analgesic
Antidiarrhea - codeine can cause constipation
Pholcodine
Few side effects than codeine
Ethyl morphine
More potent and longer-acting
Thebaine
Has stimulatory effect
Conjugated diene system - synthesis of novel codeine and morphine analogue -
naturally occurring synthetic intermediate
Oxycodone
Analgesics for moderate to severe pain
Oxymorphone
Alternative to morphine - similar potency
Naloxone
Occupies morphine receptors - result in complete lack of agonist receptors
Safest anatgonist for opium overdose
:star: :star:
Etorphine
Immoblise large mammals
Buprenorphine
Affinity for μ-receptor - longer duration of action
Very low dependence liability - lower than codeine
Papaverine
Fro mother liquors from the extraction of morphine from opium
Vasodilator
Spasmolytic/antispasmodic
- due to benzyl group
Eupaverine
Less toxic
But inferior to atropine analogues
Ethaverine
3x more potent
Reduced toxicity
Verapamil
CCB
anti-arrhythmic
