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p > Lecture 9 & 10 - Opioids > Flashcards

Lecture 9 & 10 - Opioids Flashcards

1
Q

What are the CNS effects of morphine (2)

A

Elevates pain threshold, decreases brain awareness of pain

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2
Q

What are some of the side effects or morphine? (6)

A

Depression of the respiratory centre, constipation, nausea, pupil constriction, euphoria, tolerance, dependence

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3
Q

How many rings does morphine have and what shape are they in?

A

5 rings and T-shaped structure

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4
Q

Is morphine acidic or basic?

A

A functionally weak base

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5
Q

What does morphine exist as at physiological pH

A

Cation

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6
Q

What are the four types of opioid receptors?

A

MOR, KOR, DOR and ORL1 (opioid-like receptors)

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7
Q

Which receptor does morphine bind most strongly to?

A

MOR instead of DOR and KOR

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8
Q

What type of receptor is the opioid receptor

A

GPCR

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9
Q

Where does morphine bind to in the MOR?

A

A cavity at the extracellular edge of the receptor

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10
Q

What is the difference between opium and morphine?

A

Opium is an extract obtained form the opium poppy and contained more than 20 alkaloids, morphine is the main active alkaloid in opium.

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11
Q

Why can’t morphine poorly absorbed in the gut?

A

It is polar

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12
Q

Why is octanol used to calculate the partition coefficient?

A

It has a long hydrocarbon tail so it mimics

the amphiphilic nature of lipid membranes

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13
Q

What logP guarantees oral absorption?

A

2-5

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14
Q

What percentage of morphine is unionised at pH 7.4

A

14%

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15
Q

What is morphine’s pKA

A

8.2

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16
Q

What is the difference between morphine and normorphine

A

Normorphine has a amine group added instead of the methyl so it has increase ionisation

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17
Q

Which molecule has the highest lipophilicity?

A

Heroin

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18
Q

Which molecule has the highest relative analgesic activity?

A

6-acetylmorphine (an active metabolite of heroin)

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19
Q

Heroin is a prodrug true or false

A

True

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20
Q

What groups have been replaced in morphine to make heroin?

A

The 3-6 hydroxyl groups have been replaced with acetyl groups

21
Q

What is codeine?

A

A 3-methylether of morphine

22
Q

Is codeine a prodrug

A

Yes

23
Q

Is codeine found in opium

A

Yes

24
Q

How is codeine metabolised in the liver?

A

O-demethylation

25
Q

What re the 3 conjugations of morphine in the liver?

A

Morphine 3-glucuronide
Morphine 6-glucuronide
Morphine 3,6-glucuronide

26
Q

Which of the glucuronide conjugations of morphine is active?

A

Morphine 6-glucuronide

27
Q

Which OH group is important for morphine activity

A

The 3 hydroxyl

28
Q

Which confirmation of the target does an agonist stabilise?

A

The active conformation

29
Q

What are the three key groups for morphine activity?

A
  1. 3-hydroxyl forms hydrogen bonds
  2. Benzene rings have Van der waals interactions
  3. The N-methyl group can become charged and form ionic bonds
30
Q

What is the ‘message’ responsible for?

A

Pharmacological activity

31
Q

Which parts are responsible for the message in morphine?

A

The charged amine and phenolic group

32
Q

What is the ‘address’ responsible for?

A

Target selectivity (MOR vs KOR)

33
Q

What is responsible for the address portion of morphine?

A

The variable hydrophobic portion

34
Q

How is oxycodone generated?

A

An an extra OH group at position 14

35
Q

At which alkyl group does agonistic activity of morphine return?

A

Pentyl and hexyl

36
Q

What is one of the most potent N-alkylation substitutions?

A

Phenethylmorphine

37
Q

Why is naltrexone such an effective antagonist?

A

It has a cycylpropane group at the N-alkylation

38
Q

Which is more rapid, naloxone or naltrexone?

A

Naloxone

39
Q

Why are fentanyl and sufentanil more potent than morphine?

A
  1. Both are highly lipophilic due to a phenylethyl on N

2. Fentanyl has a phenetyl group attached to the nitrogen ring, sufentanil has a bioisosteric replacement with thiophene

40
Q

How is etorphine different from morphine and how does this influence potency?

A

Etorphine is synthesised from thebaine and is conformationall restricted

41
Q

Which rings have been removed in pethidine and norpethidine?

A

B, C and D

42
Q

What is the consequence of removing B, C and D

A

No ‘address’ concept, they bind in different manners

43
Q

What are met and leu enkphalins

A

Pentapeptides with a preference for MOR and DOR

44
Q

Dynorphin vs endorphine selectivity for receptors

A

KOR vs MOR and DOR

45
Q

Which groups are essential for the activity of met-enkephalin

A

Tyrosine phenol and amino groups

46
Q

How do you remove the activity of met-enkephalin (2)

A

Replace the tyrosine

Inactivate it using peptidase

47
Q

What provides the message in met-enkephalin?

A

The tyrosine

48
Q

Morphine vs enkephalin selectivity for for MOR, KOR and DOR

A

+++, ++, + vs +++, ___, +++

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