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PHA333 > Wk 26 - Heroin > Flashcards

Wk 26 - Heroin Flashcards

1
Q

What is heroin?

A
  • Diamorphine

- Powerful analgesic

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2
Q

What has similar effects to heroin?

A

Oxycontin + vicodin

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3
Q

Outline the pharmacokinetic of heroin

A
  • IV: greatest intensity + rapid onset euphoria (7-8 sec)
  • IM: slow onset euphoria (5-8 min)
  • Sniffed/smoked: 10-15 min
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4
Q

What is IV heroin rapidly converted to?

A

6-monoacetylmorphine + morphine by esterases in liver, plasma + CNS

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5
Q

The onset of heroin’s effect is dependent on what?

A

Method of admin:

  • Orally: 1st pass metabolism via deacetylation
  • Injected: avoids 1st pass + crosses BBB rapidly
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6
Q

In the brain what is heroin metabolised to?

A
  • 3-monoacetylmorphine

- 6-monoacetylmorphine (u opioid agonist that bind to opioid receptor)

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7
Q

How is morphine excreted?

A

Glucuronide conjugate

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8
Q

Which major enzyme systems metabolize opioids?

A
  • CYP450

- UGTs: forms glucuronides

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9
Q

Why do addicts use heroin?

A
  • Euphoria w/in 1-2 mins + high for 5hrs

- Relief from w/drawal symptoms

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10
Q

What are the w/drawal symptoms of heroin?

A

Peak: 48-72hrs + last a week

  • Drug craving
  • Restlessness
  • Muscle + bone pain
  • Cold flashes
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11
Q

What is cross tolerance?

A

Codeine, opium + morphine relieve w/drawal symptoms of heroin

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12
Q

What do endogenous opioids + exogenous opiates produce?

A
  • Pain relief, respiratory depression, miosis
  • LT: collapsed veins, abscesses, cellulitis, liver disease
  • CNS depressant
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13
Q

What opiate-like substances does the brain produce?

A
  • Pro-opiomelanocortin, pro-enkephalin + pro-dynorphin

- Cleave to form: endorphin, dynorphin, leu-enkephalin + met-enkephalin

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14
Q

Naloxone + naltrexone are antagonists all which receptor sites

A

u, k + d

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15
Q

Opioid receptors have high concentrations of what?

A
  • NTS
  • PAG
  • Cerebral cortex
  • Thalamus
  • Substantia gelatinosa
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16
Q

How do opioids work on channels?

A
  • Open K channels
  • Close Ca channels
  • Inhibit adenylyl cyclase activity
17
Q

What is the overall effect of opiates on nerve cell functions?

A
  • Red membrane excitability
  • Slow cell firing
  • Inhibit NT release
18
Q

What is the mechanism of action of heroin in the reward system?

A
  • Opioids + endogenous opioid NT activate presynaptic u opioid receptor on GABA neurons
  • Inhibit release of GABA in VTA
  • Allows dopaminergic neurons to fire more
  • Release of DA in nucleus accumbens = pleasure
19
Q

What is unassisted treatment?

A

Cold turkey

20
Q

What is assisted treatment?

A

Use clonidine or long acting opiate drug (methadone/buprenorphine)

21
Q

What are clonidine, lofexidine + guanfacine?

A

a2 adrenergic agonist:

  • Act on central + peripheral ANS
  • Red release of AD + NA
22
Q

What is clonidine?

A
  • Partial a2A agonist
  • High efficacy for opioid w/drawal
  • Fall in BP if non-hypertensive
  • Indication: HT
23
Q

What is lofexidine?

A
  • Short acting selective a2A agonist
  • Indication: symptom management of opioid w/drawak
  • Cause drowsiness, dry mouth, throat + nose, hypotension + bradycardia
24
Q

What is guanfacine?

A
  • Selective a2A agonist
  • Efficacy for opioid w/drawal + anxiety
  • Less effect on BP
  • Indication: ADHD
25
Q

What is methadone?

A
  • Slow acting opioid agonist
  • Binds to u-opioid receptor
  • Prevent heroin w/drawal for 24 hrs
  • Respiratory depression, QT prolongation + hypotenso
26
Q

What is naloxone?

A
  • Short acting opioid antagonist
  • High affinity at u-opioid receptor + low k + g
  • Poorly abs orally
  • IM/IV
  • Heroin OD
27
Q

What is naltrexone?

A
  • Non-selective competitive antagonist at u-opioid receptor
  • Displaces heroin + methadone in mins
  • Used after opioid w/drawal to prevent relapse
  • Vivitrol = injectable long acting naltrexone
  • Hepatotoxicity from chronic use
28
Q

What is buprenorphine?

A
  • Partial u-opioid receptor agonist
  • Taken 6-12hrs of heroin, 24-28hrs of methadone, will precipitate w/drawal
  • Max dose: 32mg
  • Antagonist at k + g opioid receptor red tolerance, dependence + attenuate dysphoria
29
Q

What is suboxone?

A
  • Buprenorphine + naloxone (4:1)
  • Sublingual: bup = partial antagonistic effect
  • Injected: 100% bioavailability
  • Role: alleviate w/drawal symptoms + deter IV use

PHA333 (35 decks)

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