OPIOID ANALGESICS PART I

1. Opioid analgesics
Dr Rekha nayaka m.R
Associate professor
JN medical college
Belagavi

2. Objectives-part I
 Pain pathway
 Opioid receptors
 Classification of opioid analgesics
 Morphine-In detail

3. PAIN
 It is an illdefined, unpleasant sensory &
emotional experience associated with actual
/potential tissue damage.

4. Analgesic
 A drug that selectively relives pain by acting
in the CNS / on peripheral pain mechanisms,
without significant alteration of consciousness
& relives pain of multiple origin
 Relive pain as a symptom ,without affecting
its cause

5.  Analgesics are divided in two groups
 Narcotic /opioid /morphine like analgesics
 Non narcotic / NSAIDS

13. Opioid-
Opos =Opium
papaver
somniferum

17. MORPHINE

19. MECHANISM OF ACTION

20.  MORPHINE
CNS- depressant effect
 Analgesia –strong
 Dull ,poorly localized visceral pain
 Suppression of pain is selective-without
effecting other sensation
 Perception of pain & reaction to it are altered
 Patient tolerates the pain better

21. Sedation
 Drowsiness & indifference to surrounding & his
body occurs without motor incordination/ataxia
 Higher dose- sleep ,coma
Mood & subjective effect
 Calming ,loss of appreciation ,feeling of
detachment,lack of initiation ,mental clouding &
inability to concentrate
 Unpleasant in normal & pleasure in pain
 Euphoric effect-kick , high, rush….

22. Respiratory centre-
 Depression in dose dependent manner
 Rate & tidal volume are decreased
 Death in poisoning
 Neurogenic ,hypercapnoeic & later hypoxic
drives to respiratory center are suppressed in
succession

23. Cough center supression
Vasomotor center of medulla-unaffected

24.  Morphine stimulates
 CTZ & vestibular component-nausea & vomiting
 Edinger Westpal nucleus-3rd
nerve-miosis
 Vagal centers-bradycardia
 Central cortical areas & hippocampal cells
stimulation-
Muscular rigidity immobility at higher dose

25. NEURO-ENDOCRINE
 Hypothalamic activation by afferent
collaterals is dampened –influence on
pituitary is reduced ,leading to-
reduced ACTH, FSH, LH
Increases- prolactin & GH

26. CVS
vasodilatation
 Direct action –dec tone of BV
 Histamine release
 Depression of vasomotor centers
 Shifting of blood to periphery-Cardiac work is reduced

27. GIT
Constipation
 Direct & CNS –increase in tone &
segmentation, decrease in propulsive
movement
 Spasm of pyloric, iliocecal & anal sphincter
 Decreased GI secretion
 Central action causes inattention to
defecation reflex
 No tolerance in addicts

28. Effect on smooth muscles
 Biliary tract-spasm of sphincter of oddi-increase
in intra biliary pressure-biliary colic
 Urinary bladder-tone of both sphincter &
detrusor is increased  urinary urgency &
difficult in micturation
 Uterus  insignificant, may prolong labour
 Bronchi-release of histamine 
bronchoconstriction

29. Pharmacokinetics
 Oral morphine is subject to extensive first
pass metabolism mainly glucuronide
conjugation in the gut wall and liver as result
only 20% of the dose reaches systemic
circulation
 Its preferred route are IV ,IM SC
 Yet morphine is now available for oral use in
controlled release tablet
 Freely crosses placenta

30. Clinical uses of morphine and
other opioids
 As analgesic
 Opioids are used for relief of moderate to
severe deep seated visceral pain such as
pain associated with MI, renal colic ,
traumatic, post operative and cancer pain
 Intra articular injection in knee joints for
osteoarthritis.

31.  Acute left ventricular failure (LVF)
-shift of blood from pulmonary to systemic
-depression of respiratory center
- depression of sympathetic stimulation &
cardiac load
 Cough suppressant
 Diarrhea
 Relief from anxiety and apprehension

32. ADVERSE EFFECTS
 Side effects-
 sedation ,mental clouding, lethargy
 Vomiting is rare, constipation most common
 Respiratory depression, blurring of vision,
urinary retention, fall in BP ( hypovolumic
patients)
 Allergy- urticaria ,itch , swelling of lips
 Apnea-in new born (Naloxone 10mcg/Kg in U
cord)

33.  Acute morphine poisoning
 drug abusers
dose in adult -50mg im-lethal-250mg
 CF-stupor ,coma, flaccidity ,shallow respiration, pin point
pupil, fall in BP, convulsion ,pulmonary edema, death
due to respiratory depression
 Treatment RS  +ve pressure respiration
BP  iv fluids, vasoconstrictors
 Gastric lavage-potassium permanganate (Even for iv/im)
 Specific antidote-
 Naloxone 0.4-0.8mg iv/ 2-3min till respiration
picks up
alternative –nalorphine 3-5mg iv (Obsolete)

34. TOLERANCE
 2-3wks of therapeutic dose
 Large dose in short duration of time
 High –analgesia, euphoria ,sedation, respiratory
depression, mental clouding, cough suppression
 Minimal-miosis, constipation, convulsion
Treatment –NO synthase inhibitors
--NMDA recpt antagonist

35. DEPENDENCE
Physical-failure of continuous administration-
withdrawal/abstinence syndrome
 C/F=rhinorrhea, lacrimation, chills ,yawning,
goose flesh, hyperventilation, mydriasis,
hyperthermia, muscle ache, diarrhea
 Signs of withdrawal 6-10hr, peek effect 34-45hr
Psychological -euphoria indifference to pain
,sedation, abdominal effect similar to orgasm
 Treatment - slow withdrawal of morphine &
substitute with oral methadone

36. CONTRAINDICATION & PRECAUTION
 Patients with respiratory insufficiency
 Bronchial asthma
 Head injury-retention of C02 –increase in ICT
-respiratory depression
-interfere with assessment
 Impaired hepatic & renal function
 Endocrine disease-Addison’s disease ,
hypothyroidism
 Pregnancy  withdrawal symptom in baby
 Undiagnosed  acute abdominal pain

37. INTERACTION

38. Revise to remember….