OPIUM-ALKALOIDS-PART-I

OPIOIDS-PHARMACOLOGY

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An opioid is a medical term applied to any substance which is either endogenous or exogenous or synthetic or natural and or opium alkaloids or other chemicals must act on the opioid receptors available in our body system. Generally, those who have morphine (the major alkaloidal content of opium poppy) like activities.

There are many types of opioid receptors available in our brain system but the important is Miu, delta, and kappa receptors.

These opioid receptors are situated throughout the CNS including the cerebral cortex, thalamus, brain stem, and spinal cord.

Characters of Opioid Receptors

1.Miu:-

These Miu receptors are responsible for producing spinal and supraspinal analgesia, euphoria(daydream), respiratory depression, miosis, and constipation. Most of the natural opium alkaloids especially morphine act on this.

2.Kappa:-

These receptors when stimulated they produce spinal/infraspinal analgesia, dysphoria(a feeling of dissatisfaction), sedation, and miosis

3.Delta:-

These receptors are mild and responsible to produce only analgesia.

Naturally Available Opioids:-

Our body has a natural pain-relieving system that contains endogenous opioids. They are enkephalins, endorphins, and dynorphins. Even if we do not take any painkillers our body can able to get relieved from the pain after some days with the help of these endogenous natural opioids.

Opioid Pharmacology

These opioids have the power of stimulating the Chemoreceptor Trigger Zone(Vomit Center) and blocking alpha-adrenergic receptors.

OPIUM ALKALOIDS-MORPHINE

Morphine is the major alkaloid of opium poppy seeds exudate and is responsible for the major addictive nature of opium. Morphine is highly unstable and its toxicity and addictive nature exceed its medical value. But it gives a way for the production of many medically valued structurally modified and synthetic analogs.

Morphine Structure:-

In the above structure, the 'A' part is known as the phenolic group with its typical benzene aromatic ring attached with a phenolic OH- group at the 3rd position. Hence morphine and all its analogs are chemically phenolic compounds with a slightly acidic nature. But their analgesic character is purely due o the presence of the chair like piperidyl ('D')group. Basically, it is a combined structure of p-phenyl-N-methyl piperidine which is responsible for the analgesic character.
A variety of morphine analog with structural modifications and synthetics should bear this piperidine moiety in common.

Modified Analogues:-

1.Codeine

2.Diamorphine(Heroin)

3.Hydromorphone

4.Oxycodone

Synthetic Analgesics

1.Meperidine

2.Diphenoxylate

3.Methadone

4.Propoxyphene
5.Dextromethorphan

Non-Related Opioid

1.Tramadol

Full Agonists

 

1.Morphine

2.Meperidine

3.Methadone

4.Fentanyl

5.Diamorphine

6.Hydromorphone

Partial Agonists

1.Codeine

2.Propoxyphene

3.Oxycodone

4.Hydrocodone

5.Buprenorphine

Partial agonists produce lesser than full effect even though they bind to all the receptors.

Mixed Agonists and Antagonists

1.Pentazocine

2.Nalbuphine

3.Butorphanol

These receptors agonize some receptors and block other receptors

Full Antagonists

1.Naloxone

2.Naltrexone