10th

Pain Management in Dentistry-2

Action of Opioids
On the CNS-more specifically, on three main classes of opioids:
 receptor: responsible for producing SC analgesia, euphoria, respiratory depression, miosis and constipation.

 receptor: responsible for producing SC analegia, sedation, dysphoria, and miosis.

 receptor: responsible for producing SC analgesia
• These receptors are located throughout the CNS including the cortex, thalamus, brain stem, and SC

Opioids

Used to produce:
Euphoria
Analgesia
Sedation
Relief from Diarrhea
Cough Suppression

Morphine

MoA: Strong affinity for u, kappa and delta receptors.
Effects and Medical Uses:
Histamine and Hormonal actions
Emesis
Contraction of biliary smooth muscle and
Cardiovascular changes-orthostatic hypotension at high doses
Decreased cough reflex, Decreased GI motility, and Depression of mental functioning (sedation)
Respiratory depression -Fatalities can occur at high doses.
Euphoria
Analgeisa-Opioids are the most potent drugs available for relief of pain.
Miosis

Morphine

Therapeutical used:

Analgesia

Diarrhea
Relief of cough


Withdrawal symptoms are seen with opioids
Chills
Diarrhea
Myalgia
Agitation
Anxiety

Dextromethorphan: A nonopioid derivative of morphine used as an anti-cough agent

Meperidine
Primarily stimulate the μ receptor.
It does not produce pinpoint pupils like other opiates, but rather causes the pupils to dilate because of its anti-cholinergic activity similar to that of atropine.
Loperamide: a meperidine analogue used to treat diarrhea.
Tremor, Convulsions and muscle twitches.

Meperidine Derivates

1-Methadone
Used primarily for narcotic detoxification.
Because of its long half-life , methadone can prevent an addict from suffering severe withdrawal symptoms as the body normalizes.
Its effect is like morphine


2-Fentanyl
Agonist at the u receptor
Most effective opiate analgesic
80-85% plasma protein bound
Oral and Transdermal
80 times the analgesic potency of morphine and 10 times the analgesic potency of hydromorphone
Therapeutically: used for anesthesia
used for chronic and post-operative pain.

Heroin

Heroin is hydrolyzed into morphine and therefore has properties similar to morphine.
More lipid soluble and crosses the BBB more quickly than morphine.

Partial Agonists

Codeine: low affinity for μ receptors.
It’s a potent anti-tussive to relieve mild to moderate pain.
Very similar to morphine

Partial Agonist

Propoxyphone: at the μ receptors
Therapeutically: used for analgesia
SE: Cases of convulsion and hepatotoxicity


Hydrocodone: at the μ receptor
As an adverse effect: releases Histamine

Partial Agonist

Oxycodone: works at the μ receptor
Similar to morphine

Buprenorphine

Similar to morphine
It’s a partial μ agonist. It dissociates from the u receptors slowly, which may contribute to its long duration of action and low physical dependence.

Opioid Antagonist

Naloxone
Binds all opioid receptors to displace bound opioid agonists.
Duration of action: 1-2 hours. This is important because patients may relapse into respiratory depression and coma if repeated dosages of naloxone are not given.
Naltrexone
Binds at all opioid receptors
Beneficial for treating opioid dependency because it has a longer duration of action than naloxone.

Other Analgesics- Tramadol

is a centrally acting analgesic that binds to the μ-opioid receptor.
In addition, it weakly inhibits reuptake of norepinephrine and serotonin.
It is used to manage moderate to moderately severe pain.
Its respiratory-depressant activity is less than that of morphine