2. Analgesic
Are drugs which relieve pain without causing
loss of consciousness
OPIATES: product obtained from the opium
poppy.
OPIOID ANALGESIC: naturally occurring
semi synthetic or synthetic drugs which have
action of relief of pain and depression of CNS.
NARCOTICS ANALGESIC: old term for
opioid analgesic
3. Opioid receptors
These opioid acts through receptors
present in CNS and pheripheral tissue.
Following and there functions
1) µ(mu) : analgesia (supraspinal) ,
respiratory depression, euphoria ,sedation
and physical dependence
2) k(kappa) : analgesia (spinal),
dysphoria , sedation
3) δ delta : analgesia( supraspinal and
spinal )and emotional behaviour
4. CLASSIFICATION OF
OPIOID
NATURAL OPIUM
ALKALIODS
a) phenanthrene derivatives
b) benzylisoquinoline derivatives
Morphine , Codeine
Thebaine
Papaverine
Noscapine
Semisynthetic derivative Heroin
dihydromorphine
apomorphine
Synthetic substitutes Pethidine
methadone
fentanyl
tramadol
5. MORPHINE
Natural opium alkaloid
Opium is the milky exudate of unripe capsules of
the poppy plant (Papaver somniferum)
Classified into
Phenanthrene group : morphine , codeine,
thebaine
Benzylisoquinoline group : papaverine,
noscapine and narcine
6. Pharmacological action
ANALGESIC : relieves severe pain like visceral
pain and pain of trauma
mechanism
1) it elevates the pain stimulus
2) alters emotional reaction to pain
3) produce sleep
CNS : in presence of pain it produces euphoria , absence
of pain produces dysphoria. Increased dose produce
sleep
Respiration: depression of respiration by
a) directly depressing the respiratory centre
b) decreasing the sensitivity of respiratory centre to CO2
7. Pupil : constriction of pupil. This effect will block by
atropine. ..addicts have constricted pupil
Emetic action : in small doses produce vomiting due to
stimulation chemoreceptor trigger zone . In large doses
morphine inhibits vomiting.
Antitussive effect: suppresses cough by depressing
cough center
ADH secretion: release of ADH which results in
decrease in urine output
GIT: decreases peristaltic movements .
It produces spasm of intestinal smooth muscles and
spincters .It increases the absorbtion of water leads to
constipation
CVS : normal dose – no effect
toxic dose produces hypotension
8. Absorption, fate and excretion
Absorption from GIT is slow and incomplete.
Quick effect on subcutaneous inj
Metabolised by conjugation with glucuronic acid
Excreted in urine within 24hours
9. preparation and dose
1) Tincture opium – 0.3 to 2ml by
mouth
2) Morphine sulphate - 8 to 20mg by
mouth or injection
3) Morphine hydrochloride - 8 to 20mg
by mouth or injection
10. ADR
CNS: dysphoria and mental clouding
GIT: nausea, vomit, constipation
Tremor, delirium, skin rshes
Acute morphine poisoning- respiratory
depression, miosis, cynosis, reduced body
tempertaure, hypotension,shock and coma
Depression of foetal respirtion
Drug dependence
11. uses
Analgesic
Treat diarrhoeas
Sedation
Pre aneasthetic medication
Acute left ventricular failure
antitussive
12. Codeine
It is phenanthrene alkaloid.
It has antitussive effect..used to treat
cough, nausea, vomiting, miosis,
addiction are less with codeine.
Less potent analgesic when compared
to morphine
13. PETHIDINE
Synthetic compound
It produces same as morphine
1) analgesic effects
2)spasmogenic effect on smooth muscles and
spincters
3) nausea and vomtting
4)sedation and euphoria
5)respiratory depression
But pethidine does not produce miosis and anti
tussive effect
14. Absorption : well on oral and parenteral.
Metabolised : liver
Excrete : urine
ADR: local irritation on parentral administration
dry mouth, nausea, vomiting
euphoria, dysphoria, coma, convulsions
weakness, palpitation, respitaory depression
depression of foetal respiration
addiction and tolerance
Preparation and dose:
1) pethidine hydrochloride tablets: 25 to 100mg
2) pethidine hydrochloride inj : 25 to 100mg by
subcutaneous or i.m inj and 25 to 50mg by i.v
inj
15. Fentanyl
Pethidine congener
It is 80 to 100 times more potent than morphine.
Highly lipid soluble. So it enters brain easily.
Peak analgesic effect produced in 5 min after
inj.
Duration of action slow.
Used as neuroleptanalgesia
16. Methadone
Synthetic opioid
It has analgesic effect, depressant, emetic
similar to morphine
Used in opioid dependence
Mechasim : it acts in tissues
On discontinuation it is slowly released from
tissues. Mid withdrawal symptoms are mild
17. Tramadol
It is centrally acting analgesic.
Use for post operative pain, chronic pain, labour
pain
Addiction is low