Chapter 13 Opioids

Question 1

What is an opioid?

Answer 1

A substance that binds to opioid receptors

Question 2

What opioids are sourced from the opium poppy?

Answer 2

Opium, codeine, morphine, and heroin

Question 3

What are endogenous opiates?

Answer 3

Peptide neurotransmitters, like beta-endorphins

Question 4

What were the old uses for opioids?

Answer 4

Sleep, pain, depression, and more. It was also used to sooth crying babies

Question 5

What are the current legitimate medical uses for opioids?

Answer 5

Pain relief, cough suppression, and antidiarrheal.

They also have euphoric effects, which result in abuse liability and respiratory depressant effects, which can be lethal

Question 6

What routes can opioids be administered?

Answer 6

Any route. Oral is most common, but injection is preferred for recreational use and immediate relief of severe pain. Patches are favored for continuous delivery of pain relief

Question 7

What are the non-medical uses of opioids?

Answer 7

To enhance imagination and broaden perspectives. More commonly opioids have been used for purely recreational purposes, or to avoid withdrawal symptoms.

Question 8

What is the main difference between heroin and the traditional opioid morphine?

Answer 8

Heroin permeates the BBB faster.
Many users move to heroin when it’s easier to get, or cheaper. Because of cost and/or tolerance, users will often escalate to injection of heroin or dissolved pills

Question 9

What are the effects of morphine and related drugs?

Answer 9

• Nausea and vomiting (can be prevented by anti-nausea agents such as ondansetron)
• euphoria
• relaxation and sleepiness
• itching (due to histamine release)
• constipation
• somewhat decreased immune respone
• tolerance and dependence can ensue

Question 10

What are the withdrawal symptoms of morphine and related drugs?

Answer 10

• dysphoria and depression
• anxiety and fearfulness
• runny eyes and nose, sweating
• restlessness and yawning
• vomiting
• pain and aching
• diarrhea (can be fatal in newborns born to dependent mothers)
• craving

Question 11

What are the three types of opioid receptors?

Answer 11

Mu, kappa, and delta

Question 12

What does the mu opioid receptor do?

Answer 12

Mediates analgesia, euphoria, and respiratory depression

Question 13

What doe the kappa opioid receptors do?

Answer 13

Produce modest analgesia, dysphoria, some hallucinatory effects; may be involved in opioid withdrawal syndrome

Question 14

What do the delta opioid receptors do?

Answer 14

They’re not well understood, but they may work for chronic pain; may be an antidepressant. Delta agonists do not seem to have abuse liability or respiratory suppression, but they can cause seizures

Question 15

What is the mechanism of action for opioids?

Answer 15

Opioid receptors are found the presynaptic surface of neurons, on the boutons. When they are bound, they decrease the release of neurotransmitters. Analgesic effects are mediated via the nociceptive pathways

Question 16

What do nociceptive neurons do?

Answer 16

They carry pain information away from the site of injury to the spinal cord where the synapse onto pain pathways in the spinal cord.

The neurotransmitters at this synapse include a peptide called “Substance P” and glutamate. Information is the carried to certain areas of the brain: somatosensory pathways and areas involving emotion

Descending pathways from the brain are activated, which reduce the activity in the ascending pathways by releasing endorphins on them

Question 17

During what stages of mechanism of action do opioids mediate pain?

Answer 17

All of them. They inhibit Substance P in the ascending pathways, so pain information doesn’t completely make it to the brain

They have a calming effect, so the pain that does arrive is perceived as less upsetting

They increase activity of descending pathways

Question 18

How does euphoria occur?

Answer 18

Some neurons release dopamine into the reward pathways such as the nucleus accumbens, and are moderated by GABA. When GABA is released onto the neuron, they in turn release less dopamine.

Opioids block GABA release, which results in less inhibition of dopaminergic neurons. They release more dopamine into the reward pathways and thus cause feelings of euphoria and pleasure

Question 19

What is Buprenorphine (Suboxone, or part of Subutex)?

Answer 19

A mu partial agonist with high affinity and moderate efficacy. It suppresses withdrawal, but can have abuse potential itself (schedule III) especially if it’s injected. The effects plateau rather than escalate with higher doses. Physicians can prescribe it, but they need a permit to prescribe it to more than 30 people.

Question 20

What is methadone?

Answer 20

A full agonist with high affinity and efficacy. Generally taken orally and dispensed to licensed clinics. Long half-life means that withdrawal isn’t quite as bad as with heroin. Ideally it is continued after a period of use; in reality it is often used for an extended period.

Question 21

What is Naltrexone?

Answer 21

An opioid antagonist that can be given orally or as an extended-release injection. Unlike methadone or buprenorphine, it doesn’t reduce withdrawal and in fact will precipitate them if the person’s not fully detoxed