Morphine is the principal alkaloid found in opium and is widely used as an analgesic. It acts primarily in the central nervous system to reduce pain perception and induce sedation. Morphine is classified as a natural opium alkaloid and binds to mu opioid receptors in the brain to reduce neurotransmitter release. Common adverse effects include sedation, respiratory depression, constipation, and risk of dependence with chronic use. Morphine and other opioid analgesics are used to treat severe acute and chronic pain.

1. ANSUMAN SAHU
OPIOID ANALGESICS

2. Algesia (pain) is an ill-defined, unpleasant
sensation, usually evoked by an external or
internal noxious stimulus.
Analgesic - A drug that selectively relieves pain by
acting in the CNS or on peripheral pain
mechanisms, without significantly altering
consciousness.

3. OPIOID ANALGESICS :
Opium A dark brown, resinous material obtained
from poppy (Papaver somniferum) capsule.
It contains two types of alkaloids.
 Phenanthrene derivatives
Ex - Morphine (10% in opium)
Codeine (0.5% in opium)
Thebaine (0.2% in opium), (Nonanalgesic)
 Benzoisoquinoline derivatives
Ex - Papaverine (1%) Nonanalgesic
Noscapine (6%)

4. CLASSIFICATION OF OPIOIDS :
1. Natural opium alkaloids: Morphine, Codeine
2. Semisynthetic opiates: Diacetylmorphine
(Heroin), Pholcodeine.
Many others like—Hydromorphone,
Oxymorphone, Hydrocodone, Oxycodone, are not
used in India.
3. Synthetic opioids: Pethidine (Meperidine),
Fentanyl, Methadone, Dextropropoxyphene,
Tramadol.

5. MORPHINE :
Morphine is the principal alkaloid in opium and still widely
used.
PHARMACOLOGICAL ACTIONS :
1. CNS
(a) Analgesia : Morphine is a strong analgesic. Though
dull, poorly localized visceral pain is relieved better than
sharply defined somatic pain; higher doses can mitigate
even severe pain—degree of analgesia increasing with
dose.
(b) Sedation
(c) Mood and subjective effects : Morphine has a
calming effect; there is loss of apprehension, feeling of
detachment, lack of initiative, limbs feel heavy and body
warm, mental clouding and inability to concentrate
occurs.

6. (d) Respiratory centre : Morphine depresses
respiratory centre in a dose dependent manner
(e) Cough centre : It is depressed; more sensitive
to morphine than respiratory centre.
(f) Temperature regulating centre : It is
depressed; hypothermia occurs in cold
surroundings.
(g) Vasomotor centre : It is depressed at higher
doses and contributes to the fall in BP.
2. Neuro-endocrine Hypothalamic activation by
afferent collaterals is dampened. Hypothalamic
influence on pituitary is reduced. As a result FSH,
LH, ACTH levels are lowered, while prolactin and
GH levels are raised

7. 3. CVS : Morphine causes vasodilatation due to:
(a) histamine release.
(b) depression of vasomotor centre.
(c) direct action decreasing tone of blood vessels.
4. GIT : Constipation is a prominent feature of
morphine action.
5. ANS : Morphine causes mild hyperglycaemia
due to central sympathetic stimulation. It has
weak anticholinesterase action.

8. ADVERSE EFFECTS :
1. Side effects - Sedation, mental clouding,
lethargy.
2. Idiosyncrasy and allergy - Allergy is uncommon
and anaphylactic reaction is rare. Urticaria, itch,
swelling of lips are the manifestations.
3. Apnoea - This may occur in the newborn when
morphine is given to the mother during labour.
4. Acute morphine poisoning - It is accidental,
suicidal or seen in drug abusers.
5. Tolerance and dependence - High degree of
tolerance can be developed to morphine and
related opioids if the drug is used repeatedly

9. PRECAUTIONS AND CONTRAINDICATIONS :
1. Infants and the elderly are more susceptible to the
respiratory depressant action of morphine.
2. It is dangerous in patients with respiratory
insufficiency, sudden deaths have occurred.
3. Bronchial asthma: Morphine can precipitate an
attack by its histamine releasing action.
4. Head injury: morphine is contraindicated in patients
with head injury.

10. USES :
1. As analgesic - Opioid analgesics are indicated in
severe pain of any type.
2. Preanaesthetic medication
3. Relief of anxiety and apprehension
4. Acute left ventricular failure (cardiac asthma)
5. Cough - Codeine or its substitutes are widely
used for suppressing dry, irritating cough
6. Diarrhoea - The constipating action of codeine
has been used to check diarrhoea and to
increase the consistency of stools in colostomy

11. OPIOID RECEPTORS :
1. μ ( Meu) receptor
2. κ ( Kappa ) receptor
3. δ ( Delta ) receptor
Opioid receptor activation reduces intracellular
cAMP formation and opens K+ channels (mainly
through μ and δ receptors) or suppresses voltage
gated Ca2+ channels (mainly κ receptor). These
actions result in neuronal hyperpolarization and
reduced availability of intracellular Ca2+ →
decreased neurotransmitter release by CNS and
myenteric neurones

12. OPIOID ANTAGONISTS :
1. Agonist-antagonists (κ analgesics)
Ex -Nalorphine, Pentazocine, Butorphanol
2. Partial/weak μ agonist + κ antagonist
Ex - Buprenorphine
3. Pure antagonists
Ex - Naloxone, Naltrexone, Nalmefene

13. Thanks