Opioids Agonist and Antagonist

What structural modification converts morphine into naloxone?

Allyl substitution on nitrogen plus addition of hydroxyl group

Which receptor mediates most opioid analgesia?

Mu-opioid receptor

Which endogenous opioid peptides derive from POMC?

Beta-endorphin and met-enkephalin

Which precursor protein yields dynorphins?

Preprodynorphin

Which receptor does dynorphin primarily activate?

Kappa receptor

What effect is associated with elevated dynorphin levels?

Hyperalgesia and increased pain

Which receptor system is also called NOP?

ORL1 receptor

What is unique about nociceptin compared to dynorphin?

Lacks N-terminal tyrosine

Which opioids are effective orally due to reduced first-pass metabolism?

Codeine and oxycodone

Which opioid accumulates in fatty tissue due to lipophilicity?

Fentanyl

Which tissue serves as main opioid reservoir despite lower concentration?

Skeletal muscle

What is the primary excretion route of opioids?

Renal excretion of glucuronides

Which morphine metabolite causes CNS excitation?

Morphine-3-glucuronide (M3G)

Which morphine metabolite prolongs opioid effect?

Morphine-6-glucuronide (M6G)

Which transporter inhibition increases M6G levels?

P-glycoprotein inhibition

Which CYP enzyme metabolizes fentanyl?

CYP3A4

Which CYP enzyme metabolizes codeine?

CYP2D6

Which CYP enzyme metabolizes methadone?

CYP2B6

What is heroin metabolized into first?

Monoacetylmorphine

Which enzyme hydrolyzes heroin?

Esterases

Which opioid metabolite can cause seizures in renal failure?

Normeperidine

What is the main mechanism of opioid analgesia?

Activation of Gi/o coupled receptors

What are the two main neuronal effects of opioids?

Close Ca channels and open K channels

What is the presynaptic effect of opioids?

Reduced neurotransmitter release

Which neurotransmitters are inhibited by opioids?

Glutamate, ACh, NE, serotonin, substance P

Where are opioid receptors highly concentrated?

Dorsal horn of spinal cord

What is the effect of opioids on ascending pain pathways?

Inhibition

What is peripheral opioid effect?

Reduced sensory neuron activity

What immune-derived opioid peptide activates peripheral receptors?

Beta-endorphin

What causes opioid tolerance?

cAMP upregulation or receptor recycling

Why does morphine cause tolerance more readily?

Fails to induce receptor endocytosis

Which drug can block opioid tolerance?

Ketamine

What paradoxical effect can chronic opioids cause?

Hyperalgesia

Which receptors mediate opioid-induced hyperalgesia?

NMDA and bradykinin receptors

What is a hallmark sign of opioid overdose?

Miosis

Which CNS effect involves decreased REM sleep?

Sedation

What respiratory change occurs in opioid overdose?

Increased PCO2

Which effect can cause airway obstruction?

Cough suppression

Which condition is associated with truncal rigidity?

Highly lipophilic opioids

What brain region triggers nausea in opioids?

Chemoreceptor trigger zone

Which receptor activation causes hyperthermia?

Mu receptor

Which receptor activation causes hypothermia?

Kappa receptor

What GI effect is caused by opioids?

Constipation

What biliary effect do opioids cause?

Sphincter of Oddi contraction

What renal effect is caused by opioids?

Urinary retention

What endocrine hormone is increased by opioids?

Prolactin

What hormone is decreased by opioids?

Luteinizing hormone

What skin effect occurs due to histamine release?

Pruritus

What immune effect do opioids have?

Suppress immune function

Which pain is best treated by opioids?

Severe constant pain

Which pain is poorly treated by opioids?

Sharp intermittent pain

Which opioid is preferred in labor due to less neonatal depression?

Meperidine

What is opioid rotation?

Switching opioids to reduce tolerance

What drug is used for opioid detoxification?

Methadone

Which alpha agonist reduces withdrawal symptoms?

Clonidine

What is antagonist-precipitated withdrawal?

Withdrawal induced by naloxone

Which drugs can induce withdrawal due to mixed activity?

Pentazocine, nalbuphine

What is MAT?

Medication-assisted treatment

Which drugs are used in MAT?

Methadone, buprenorphine, naltrexone

Why avoid partial agonists with full agonists?

May precipitate withdrawal

Why avoid opioids in head injury?

Increase intracranial pressure

Which condition increases opioid sensitivity?

Hypothyroidism

Which opioid class includes morphine?

Phenanthrenes

Which opioid is a phenylheptylamine?

Methadone

Which opioid class includes fentanyl?

Phenylpiperidines

Which fentanyl analog is most potent?

Sufentanil

Which fentanyl analog has shortest duration?

Remifentanil

Which opioid is used in veterinary medicine and highly potent?

Carfentanil

Which opioid has antimuscarinic effects?

Meperidine

Which opioid has SNRI and NMDA antagonist properties?

Levorphanol

Which opioid has lowest potency among moderate agonists?

Propoxyphene

Which drugs treat diarrhea among opioids?

Loperamide, diphenoxylate

Which opioid is partial agonist and kappa antagonist?

Buprenorphine

Why is buprenorphine resistant to naloxone reversal?

High receptor affinity

Which drug is combined with buprenorphine to prevent misuse?

Naloxone

Which opioid is kappa agonist and mu antagonist?

Nalbuphine

Which opioid causes more sedation at equal analgesia?

Butorphanol

Which drug inhibits serotonin and norepinephrine reuptake?

Tramadol

What adverse effect is associated with tramadol?

Seizures

What syndrome can tramadol cause with SSRIs?

Serotonin syndrome

Which drug is similar to tramadol but stronger NET inhibition?

Tapentadol

Which opioid is used as antitussive and non-addictive?

Dextromethorphan

Which opioid antagonist has shortest half-life?

Naloxone

Which antagonist is orally active?

Naltrexone

Which antagonist has longest half-life?

Nalmefene

What is the mechanism of opioid antagonists?

Competitive inhibition at mu receptors

How fast do antagonists reverse opioid effects?

Within 1-3 minutes

Do antagonists develop tolerance?

No

Does withdrawal occur after stopping antagonists?

No

What is naltrexone used for?

Maintenance therapy and alcohol dependence

What structural modification converts morphine into naloxone?

Allyl substitution on nitrogen plus addition of hydroxyl group

Which receptor mediates most opioid analgesia?

Mu-opioid receptor

Which endogenous opioid peptides derive from POMC?

Beta-endorphin and met-enkephalin

Which precursor protein yields dynorphins?

Preprodynorphin

Which receptor does dynorphin primarily activate?

Kappa receptor

What effect is associated with elevated dynorphin levels?

Hyperalgesia and increased pain

Which receptor system is also called NOP?

ORL1 receptor

What is unique about nociceptin compared to dynorphin?

Lacks N-terminal tyrosine

Which opioids are effective orally due to reduced first-pass metabolism?

Codeine and oxycodone

Which opioid accumulates in fatty tissue due to lipophilicity?

Fentanyl