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Pharmacology > Opioids > Flashcards

Opioids Flashcards

1
Q

Opioids can be classified as

A

Natural opium alkaloids
(semi-synthetic drugs)
Synthetic analgesic drugs

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2
Q

Nociceptive receptors are

A

Free nerve endings distributed throughout the body, which detect a nociceptive stimulus
- Transmitted from peripheral nerves through spinal cord to numerous areas within CNS

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3
Q

Opiate

A

Drug derived from opium (unikosta)

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4
Q

Opioid

A

Drug that is not derived from opium, but interacts at the opioid receptors

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5
Q

Opioid receptors are located in

A

Brain
Autonomic nervous system
Gastrointestinal tract
Heart
Kidneys
Pancreas
Fat cells
Lymphocytes
Adrenal glands
Other tissues

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6
Q

Opioid receptors

A

mu (μ) - 2 subtypes; 1 and 2
delta (δ)
kappa (κ),
sigma (σ) (significance not understood)

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7
Q

Full opioid receptor agonists

A

Produce a dose dependent increase in effect, until maximum stimulation of the receptor is achieved

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8
Q

Partial opioid receptor agonists

A

Produce a dose-dependent increase in effect, but less than the maximum effect of full agonist

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9
Q

Opioid receptor antagonist

A

Binds to receptor and inhibits the binding of agonists, and displacing previously bound agonists due to greater receptor affinity of the antagonist

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10
Q

Natural alkaloid categorisations

A

Derivatives of phenanthrene with analgesic effect
1. Morpine
2. Codeine
Derivatives of isoquinole: spasmolytic effect
1. Papaverine

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11
Q

Semi-synthetic opioid substances

A

Received by administration of a few morphine or codeine radicals
1. Buprenorphine
2. Butorphanol
3. Heroin
4. Apomorphine (emetic drug for dawgs)
5. Oxymorphone

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12
Q

In case of overdose in opioids, what can be used

A

Nalorphine

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13
Q

Synthetic analgesic drugs

A

Not substantially different from morphine. Absorb poorly if administered through oral route.
1. Fentanyl
2. Methadone
3. Pentazocine

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14
Q

Pharmacokinetics and absorption

A

Lipophilic compounds; absorbed form both enteral and parenteral route.
Absorption slower and less complete from GI tract
Penetrate placental barrier well (unsuitable for pain relief in labour)
Primary effect site is CNS for analgesia, antitussive effects and sedation

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15
Q

P-glycoprotein efflux pump

A

Some drugs are just so to say pumped out of CNS back to blood and back to vasculature.
Affects the CNS effect - doesn’t work for opioids, but esps in case of loperamide.

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16
Q

Animals with deficiency in functional P-g pump

A

Dogs with homozygous mutations in the gene (MDRI)
- Ivermectin sensitive collies

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17
Q

Pharmacokinetics, metabolism

A

Metabolised in liver into glucuronides
>Lacking in cats - but still rapidly and
efficiently are able to eliminate
morphine by sulfate conjugation
>Codeine + synthetic analgesic drugs
go through demethylation in the
liver and byproduct is morphine

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18
Q

Affinity

A

capability to bind strongly to respective receptors

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19
Q

Activity

A

Binding to receptor causes the effect
>High affinity does not always ensure high activity

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20
Q

Potency

A

In case of opioids, linked to capability of attaching to receptors (and not the strength of analgesic effect)

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21
Q

Efficacy

A

Indicates the analgesic effect- depends on affinity and activity

22
Q

Main therapeutic effect of opioids

A

Analgesia - primary effect is to relieve of pain
Full my agonists (morphine, hydromorphone, fentanyl, remifentanyl, methadone, alfentanyl) produce most profound analgesic effects

23
Q

CNS effects of opioids

A

Dose-dependent sedation - more profoundly in combination with other sedatives (phenothiazines, a2 agonists)
>Inhibition in ca, monkey, human
>Stimulation in rest (due to differences in brain structure)

24
Q

Emetic /antiemetic effects

A

Affect the vomiting centre in trigger zone of fourth ventricle.
Low dose: emetic effect through D2 receptors
Higher/multiple doses: antiemetic effect

25
Q

In which animals do opioids have a hypothermic effect on thermoregulatory centre

A

Dogs, rabbits, monkeys

26
Q

In which animals do opioids cause a hyperthermic effect on thermoregulatory centre

A

Cats, horses ,cows, swine and goats

27
Q

In which animals do opioids cause mydriasis

A

Monkeys, cats, sheep and horses

28
Q

In which animals do opioids cause miosis

A

Dogs, rats, rabbits and humans

29
Q

Antitussive

A

Cough reducing

30
Q

Effect of opioids on cough centre

A

Strong suppression - effective in case of a dry non-productive cough
>Independent of respiratory depressant effects and analgesic effects

31
Q

Name the 2 opioid antitussives

A

Butorphanole
Hydrocodone

32
Q

Effect of opioids on respiratory centre

A

Depression (dose dependent)
Sensitivity to CO2 is weakened.

33
Q

What increases risk for respiratory depression

A
  1. Animals administered potent respiratory depressants (anesthetics)
  2. Animals with respiratory disease
  3. Animals with increased intracranial pressure (head trauma
34
Q

Effect of morphine on cardiovascular system

A

Depresses cardiac output in dogs
Increases cardiac output in horses
Hypotension in dogs caused by short-term increases in plasma histamine concentrations

35
Q

Effect of opioids on urinary tract

A

Excretion of urine is reduced - impact the release of ADH
Tone of bladder is increased, spasm of sphincters, urinary difficulties

36
Q

Effect of opioids on GI tract

A

Vomiting, Increase in tone of intestines + intestinal sphincters, reduction of peristalsis, constipation, secretion of gastric glands is reduced
>Risk of colic in horses

37
Q

Signs of opioid withdrawal

A

Nausea
Aggression
Vocalisation
Vomiting
Hyperactivity
Hyperthermia
Tremors
Salivation

38
Q

Morphine

A

Effect: analgesia - not always leading to depression of CNS
Emetic effect in ca + fe
Antitussive - unsuitable as cough medicine due to other effects

39
Q

Fentanyl

A

More potent than morphine
Causes less nausea and vomiting

40
Q

Merepidine

A

Antispasmodic (antimuscarinic effect)
Analgesic
Sedative
Causes raise in body temperature in cats
May cause bronchoconstriction in dogs

41
Q

Apomorphine

A

Induces vomiting in dogs (direct stimulation of chemoreceptor trigger zone in area postrema)
Not effective as emetic in cats
Acts as D2 agonist

42
Q

Partial opioid agonists

A

Buprenorphine (my partial agonist)
Similar effects to morphine - lower maximal efficacy
Produces less nausea and vomiting

43
Q

Butorphanol (torphadine)

A

My antagonist to partial agonist; kappa agonist
Analgesic effect in higher doses- effect less than with morphine
More effective antitussive than codeine
Antiemetic
- Can be used to prevent chemotherapy induced emesis

44
Q

Tramadol

A

a2 reuptake inhibitor
Muscarinic antagonist
Serotonin reuptake inhibitor
Effective for mild or moderate pain (mainly in dogs)
not recommended with drugs that affect serotonin receptor activation

45
Q

Toxicity of opioids

A

Strong depression of CNS
Comatose state
Respiratory depression (death from respiratory arrest, paralysis of respiratory centre)

46
Q

Antidotes for opioids

A

Opioid antagonists
1. Nalorphine
2. Naloxone
3. Naltrexone
For both natural and synthetic opiates

47
Q

Use of opioids

A

Relieving pain - provide relief for ANY kind of pain
>But due to side effects, only used if other analgesics are ineffective
Neuroleptanalgesia
>Used together with a neuroleptic - usually fentanyl + droperidol

48
Q

Neuroleptanalgesia

A

Anesthetic process that involves combining a major antipsychotic / neuroleptic or tranquiliser with a potent opioid analgesic to produce a detached pain-free state

49
Q

Contraindications

A
  1. Acute uremia
    - Stimulation of ADH release,
    excretion of urine ceases
  2. Seizure susceptibleness
    - Tetanus, epilepsy
  3. Brain trauma
    - Increase in intracranial pressure
  4. Large animals
    - Long recovery period
    - Agitation or drowsiness
50
Q
A

Pharmacology (18 decks)

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