36 terms

Opioids

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General mechanism of how opioids suppress pain
Act on spinal and supraspinal level to cause effects on somatic and visceral pain, strong effects on consciousness and act substantially more strongly than non-opioid analgesics
How do non opioid analgesics work in comparison?
Mostly have a PERIPHERAL effect - (some have central effect), effects on inflammation, weaker effects in general, no effects on visceral pain, no addiction.
Opiates vs opioids
Opiates - similar in structure to morphine with analgesic effect (natural origin, currently produced aynthetically). Drugs derived from opium.

Opioids- more synthetic, semisynthetic and endogenous opioid peptides and exogenous opioid analgesics. Used for all drugs of opiates incl synthetic etc (umbrella term)
What are the names of the opioid receptors (3)
Miu, kappa, delta
What type of receptors are opioid receptors?
G protein coupled
How do opioids work? Mechanism of action
Opioid binds to receptor --> g protein inhibition --> reduction of neurotransmitter release and inhibition of neuronal activity

Adenylylcyclase inhibition
Miu receptor - effects
Supraspinal analgesia, euphoria, sedation, miosis, git effects
Kappa receptor- effects
Spinal and peripheral analgesia, sedation, dysphoria, miosis, GIT effects
Delta receptors- effects
Spinal analgesia, breath depression, inhibition of GIT motility
Classification of opioids according to their pharmacological influence on opioid receptors
1. Agonists
2. Antagonists
3. Partial agonists (dualists), mixed agonists
4. Atypical opioids
What are the CENTRAL pharmacological effects of opioids?
- analgesia
- suppression of respiratory center
- sedation (more or less)
- suppression of anxiety
- euphoria
- antitussive effect
- nausea and vomiting
- convulsion risk
- spasms
- miosis
- increase ADH secretion
- decreased GnRH , corticotropine, fsh etc
TOLERANCE AND ADDICTION
Which are the two exceptions of effects which do not undergo tolerance with time?
Constipation and miosis
What are the PERIPHERAL effects of opioids?
- decrease git motility
- increase muscle tone of git and ut
- vasodilation and orthostatic hypotension
- histaminoliberation
- inhibition of ciliated epithelium
- fallopian tube contraction - infertility
- urine retention
- decreased uterine tone and motility -- prolongs labor
(Pharmacokinetics) Absorption of opioids
Can be parenteral, oral, perrectal, transdermal, sublingual
What is a first pass effect and do opioids exhibit it?
Yes they do
Meaning- phenomenon of a drug metabolism whereby a drug concentration is greatly reduced before it reaches the systemic circulation (fraction of drug lost during process of absorption)
(Phamarcokinetics) distribution of opioids
Parenchymatous organs, muscles, adipose tissues (lipophilic drugs such as fentanyl), pass across heb to the brain and also may cross the placental barrier
(Pharmacokinetics) biotransformation - where and what are the resulting metabolites
Where- liver
Metabolites- polar. May be active (codeine, tramadol, morphine) or inactive.
Excretion
Kidneys or liver
List of strong opioid agonists
Morphine
Methadone
Heroin
Fentanyl
Sufentanyl
Remifentanyl
Piritramid
Oxycodone ...
Pethidine
List of moderate and weak opioid agonists
Codeine
Dihydrocodeine
List of partial agonists and mixed agonists
Buprenorphine
Nalbuphine
List of atypical opioids
Tramadol
Tapentadol
List of opioid antagonists
Naloxone
Naltrexone
Nalmefen (partial agonist)
Morphine characteristics
Selective miu agonism
Oral or parenteral administration, perrectal
Morphine indications
Chronic cancer pain, post surgery pain, injuries, (MI)
Methadone characteristics
Less sedation and euphoria than morphine
Higher bioavailability after oral administration and increased half life
Opioid + NMDA receptors
What is the use - indication for methadone administration
Addiction treatment (e.g. Heroin addiction)
Benefit of methadone compared to morphine is also the longer half life which prevents plasmatic fluctuation of methadone --> less withdrawal symptoms
Fentanyl, sufentanyl, remifentanyl characteristics
Pass well across HEB
Exhibit short but STRONG analgesia (100 more than morphine)
But also strong respiratory center depression
Can cause muscle rigidity
Risk of serotonin syndrome if in combination with 5HTergic drugs
Indications of fentanyl etc
Anaesthesiology - neuroleptoanalgesia (ap+ opioid), analgosedation (bzd + opioid)
Therapy of strong pain (AMI, cancer pain)
Fentanyl is TTS - breakthrough pain and chronic pains - for breakthrough pain even better is transmucous
Piritramid characteristics
Less respiratory depression than morphine
Less emetogenic
Tolerated parenteral administration
Piritramid indications
Therapy of strong pain - post surgical, AMI..
Strong opioid prescription requires
Blue band
Pethidine characteristics
Less suppression of respiratory center than morphine
But also less analgesic potency than morphine
Metabolite is PROCONVULSIVE
Hallucinogenic
Oral and parenteral
Pethidine indications
Cancer pain
aMI pain
Etc
---- end of strong opioids ----
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Codeine
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