Medications that relieve pain without causing loss of consciousness “Painkillers”

Classes of analgesics:◦ Opioids (moderate to severe pain)◦ adjuvant analgesic drugs.

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

Gate theoryGate theory

Level of stimulus needed to produce the sensation of pain

Pain receptors: mu, kappa, and delta.

Mu, kappa and delta

Opioid drugs also react with these receptors and thus relieve pain, so these receptors also called OPIOID RECEPTORS.

Each receptor family exhibits a different specificity for the drug(s) it binds.

The analgesic properties of the opioids are primarily mediated by the μ receptors that modulate responses to thermal, mechanical, and chemical nociception.

The κ receptors in the dorsal horn also contribute to analgesia by modulating the response to chemical and thermal nociception.

Body has endogenous pain killers◦ Enkephalins◦ Endorphins

The goals of pain management include reducing and controlling pain, improving body function and quality of life.

Assist primary drugs in relieving pain, this produce synergistic effects. ◦ NSAIDs◦ Antidepressants◦ Anticonvulsants◦ Corticosteroids

Very strong pain relievers Pain relievers that contain opium, derived

from the opium poppy or chemically related to opium.

Opioid Analgesics

They can be classified according to:◦ Their chemical structure.◦ Their action at specific receptors.

Of the 20 different natural alkaloids, only three are clinically useful: morphine, codeine, and papaverine.

Relatively simple synthetic chemical modifications of these opium alakaloids are produced the three different chemical classes of opioids: morphine-like drugs, meperidine-like drugs, and methadone-like drugs.

Agonists: morphine, meperidine (pethidine), methadone, fentanyl,codeine.

Partial agonists: pentazocine, nalbuphine, buprenorphine, butorphanol.

Antagonists: naloxone, naltrexone.

Main use: to alleviate moderate to severe pain.

Opioids are also used for:◦ Cough center suppression◦ Treatment of diarrhea◦ Balanced anesthesia

Control postoperative and other types of pain.

Morphine rapidly enters all body tissues, including the fetuses of pregnant women.

Short duration of action 4 hours. Given usually I.V OR I.M Orally given is absorbed buterratic and slow. Spasm in sphincter of oddi. Lead to spasm in anal sphincter---constipation. Cerebral vasodilatation ---increase cerebral

pressure. Release histamine. Decrease the sensitivity of respiratory center

to CO2.

Is a weak analgesic compared to morphine.

It should be used only for mild to moderate pain.

Dextromethorphan a nonopioid cough suppressant, is often given instead.

Derivative from morphine Higher addiction potential. Higher euphoria. Shorter duration of action. Higher penetration to the CSF Compared to morphine.

used in Anesthesia. Used to management Postoperative

and procedural pain. Rapid onset and short duration.

Sufentanil , alfentanil , and remifentanil are three synthetic opioid agonists related to fentanyl.

They differ in potency and metabolic disposition.

Sufentanil is even more potent than fentanyl, whereas the other two are less potent and shorter acting.

These agents are mainly used for their analgesic and sedative properties during surgical procedures requiring anesthesia.

Used as analgesic. Used in the controlled withdrawal of

dependent abusers from heroin and morphine.

Methadone [METH-a-done] is a synthetic, orally effective opioid that has variable equianalgesic potency compared to that of morphine, and the conversion between the two products is not linear.

Methadone induces less euphoria and has a longer duration of action.

The actions of methadone are mediated by μ receptors. In addition, methadone is an antagonist of the N-methyl-d-aspartate (NMDA)

Used for acute pain. Can be administered orally or I.M. Meperidine is very lipophilic and has

anticholinergic effects, resulting in an increased incidence of delirium as compared to other opioids.

Meperidine [me-PER-i-deen] is a lower-potency synthetic opioid is very lipophilic and has anticholinergic effects, resulting in an increased

incidence of delirium as compared to other opioids. The duration of action is slightly shorter than that of morphine and other

opioids. Meperidine also has an active metabolite (normeperidine) that is renally excreted.

Normeperidine has significant neurotoxic actions that can lead to delirium, hyperreflexia, myoclonus, and possibly seizures.

Due to the short duration of action and the potential for toxicity,meperidine should only be used for short-term (≤48 hours) management of pain. Other agents are generally preferred.

Meperidine shouldnot be used in elderly patients or those with renal insufficiency, hepatic insufficiency, preexisting respiratory compromise, or concomitant or recent administration of MAOIs.

Serotonin syndrome has also been reported in patients receiving both meperidine and selective serotonin reuptake inhibitors (SSRIs).

partial agonists used for opioid detoxification Mixed agonist-antagonist

Contraindicated in: Known drug allergy Severe asthmaUse with extreme caution if: Respiratory insufficiency Elevated intracranial pressure Sleep apnea

Euphoria CNS depression Nausea and vomiting Urinary retention Diaphoresis and flushing Constipation

naloxone I.V (Narcan): half-life is about 1 hour.

naltrexone oral (Revia), has longer duration of action.

These drugs are used in the management of both opioid overdose and opioid addiction( block the effect of any future opioid dose)

When treating an opioid overdose or toxicity, the nurse must recognize the signs and symptoms of withdrawal.

A gradual dosage reduction after chronic opioid use, when possible, generally helps to minimize the risk and severity of withdrawal symptoms.

Stimulation of the patient may be adequate to reverse mild hypoventilation.

Is this is unsuccessful, ventilator assistance using a bag and mask or endotracheal intubation may be needed to support respiration.

Administration of opioid anatagonists may also necessary to reverse severe respiratory depression.

Co-administration of opioids with:◦ Alcohol.◦ Antihistamines.◦ Barbiturates.◦ Benzodiazepine.

Can result in additive respiratory depression, seizures, and hypotension.

Mechanism of action: It blocks peripheral pain impulses by inhibition of

prostaglandin synthesis.

It also lowers febrile body temperatures by acting on hypothalamus.

Mild to moderate pain Fever Alternative for those who cannot take aspirin

products

Contraindications: known allergy, severe liver disease and G-6-PD

Adverse effects: is generally well tolerated. Possible adverse effects include rash, nausea and vomiting.

Overdose, causes hepatic necrosis: hepatotoxicity.

Long-term ingestion of large doses also causes nephropathy

Recommended antidote: acetylcysteine regimen : is more effective when given within 10 hours of overdose. It is available as IV and OP dose.

Maximum daily dose for healthy adults is 4000 mg/day

◦ 2000 mg for elderly or those with liver disease

It is a centrally acting analgesic. Weak bond to the mu receptors and inhibit

reuptake of both norepinephrine and serotonin.

Adverse effects are include drowsiness, dizziness, headache, nausea, constipation and respiratory depression.

Before beginning therapy, perform a thorough history.

Assess for potential contraindications and drug interactions

Perform a thorough pain assessment, including pain intensity and character, onset, location, description, precipitating and relieving factors, type, remedies, and other pain treatments◦ Assessment of pain is now being considered a

“fifth vital sign”◦ Rate pain on a 0 to 10 or similar scale

Be sure to medicate patients before the pain becomes severe so as to provide adequate analgesia and pain control

Pain management includes pharmacologic and nonpharmacologic approaches; be sure to include other interventions as indicated

Patients should not take other medications or over-the-counter preparations without checking with their physician

Instruct patients to notify physician for signs of allergic reaction or adverse effects

Ensure safety measures, such as keeping side rails up, to prevent injury

Withhold dose and contact physician if there is a decline in the patient’s condition or if vital signs are abnormal, especially if respiratory rate is less than 10 to 12 breaths/min

Monitor for adverse effects. Monitor for therapeutic effect.