Mini test 2 - Analgesics

Types of Pain

• Acute

• Chronic

  • Neuropathic

  • Nociceptive

  • Radicular pain

Acute pain

New, usually of rapid onset and of concern

Chronic pain

Long-standing, constant

Neuropathic pain

pain as a result of damage to or dysfunction of nervous system

Nociceptive pain

pain response due to injury to tissues

Radicular Pain

pain along the course of a dermatome due to irritation of a nerve root

Nonopioid Analgesic

• Acetaminophen

• NSAIDs

• Local anesthetics

NSAIDs

nonsteroidal anti-inflammatory drugs

Aspirin and Ibuprofen

Local anesthetics

Lidocaine

Acetaminophen: MECHANISM OF ACTION

Acts directly on hypothalamus/ unknown

Acetaminophen: EFFECTS ON THE BODY

Acetaminophen: INDICATIONS FOR USE

Mild to moderate pain

Fever

Alternative for those who cannot take aspirin products

Acetaminophen: CONTRAINDICATIONS

Acetaminophen: SIDE/ADVERSE EFFECTS

Liver damage (overdose)

Hypertension (with daily use, particularly women)

Antipyretic

reduces fever

Reyes syndrome

Syndrome which is an acute encephalopathy (inflammation of the brain). Usually follows a viral illness & linked to intake of aspirin. Use acetaminophen (not aspirin) to reduce fever with child with a communicable disease (virus) to prevent this.

Anti-Prostaglandins

ASA, acetaminophen, and NSAIDs

- inhibit prostaglandin synthesis

- regulate cell function and inflammatory response.

COX-1 Enzymes

COX-1 is present in all tissues and cell types

COX-2 Enzymes

COX-2 also present in many tissues but in small amounts, is inactive until stimulated by pain or inflammation

Prostaglandin inhibitors

Aspirin, acetaminophen and NSAIDS can also be called anti-prostaglandins because....

they inhibit the synthesis of prostaglandins.

Reasons for taking prostaglandin inhibitors

Pain- especially acute

Fever

Inflammation

Osteoarthritis

Gout

Salicylates

aspirin

Aspirin Pharmacokinetics

oral

rectal

for pain and inflammation

Aspirin (ASA) Action

Inhibits prostaglandin synthesis and inhibits platelet aggregation.

Aspirin Adverse Effects

Stomach upset, increased bleeding, heartburn, nausea, and gastric ulceration, perforation, or bleeding.

Aspirin Contraindications & Cautions

Peptic ulcer disease, bleeding disorders, children with viral infections (Reye's syndrome), and renal dysfunction.

Aspirin Nursing implications

- Herbs can increase or decrease effects

- Full glass of water, with food or following

- Avoid crushing (faster absorption, AE, toxicity)

- Enteric Coated

- Low Dose (81 mg)

- High Dose (325-650 mg, up to 8,000 mg/day)

Signs of Aspirin Toxicity (Salicylism)

Dizziness, tinnitus (ringing in the ears), and mental confusion.

Acetaminophen (Tylenol)

A nonnarcotic analgesic and antipyretic that acts directly on the hypothalamus to reduce pain and fever.

Acetaminophen Pharmacokinetics

oral - 30-120min

MAX 4g for adult and 3g for elderly

Pain and inflammation

Acetaminophen Adverse Effects

Hepatotoxicity, renal failure, and myocardial damage.

Acetaminophen and Alcohol Risk

Chronic alcohol use depletes glutathione stores and increases toxic metabolites, raising liver damage risk.

Ibuprofen Action

Reversible inhibition of COX-1 and COX-2 to provide anti-inflammatory, analgesic, and antipyretic effects.

NSAIDS pharmacokinetics

Onset 1 hour, Peak 1 to 2 hours, Duration 6 to 8 hours

NSAIDs Nursing Considerations & Education

Do not exceed 3200 mg max daily dose.

NSAID contraindications

Reactions common in patients with:

- Rhinitis, asthma, chronic urticaria (hives), and nasal polyps

NSAID patient education

Take with food to minimize GI upset, drink 2 to 3 quarts of liquid daily

Analgesics and Hypertension Risk

Higher daily doses of acetaminophen and NSAIDs independently increase the risk of hypertension.

The Cyclooxygenase Connection (Good vs Bad)

GOOD:

COX-2 inhibition reduces pain/inflammation, while

BAD:

COX-1 inhibition causes gastric erosion, bleeding, and renal impairment.

Breakthrough pain

◦Intense pain that 'breaks through' the pain control regime

Ceiling effect

◦When the drug is no longer able to produce effect above a particular dosage.

Opioid-Naïve:

denotes a person who has not recently taken enough opioid on a regular enough basis to become tolerant to the opioid's effects

Opioid tolerant

Taking 60 mgs of morphine or equivalent for a week or longer

Patient-controlled analgesia (PCA)

a drug delivery system that uses a computerized pump with a button the patient can press to deliver a dose of an analgesic through an intravenous catheter

Endogenous Analgesia

Endorphins

Enkephalins

Dynorphin

Opioid Agonists

MORPHINE

◦Bind to opioid receptors (Mu, kappa) in the brain and spinal cord

◦Activates the endogenous analgesia system, mimics action of endogenous opioid peptides

Opioid Agonists: Pharmacokinetics

◦Metabolized: liver

◦Excreted: urine, bile

◦T1/2: 1.5-2 hours

Opioid Agonists: USES

- Prevent or relieve severe acute or chronic pain

- Before, during & after surgery

- Before & during diagnostic procedures

- Labor & delivery

Opioid Agonists: Routes

PO

IV

IM

Subcutaneous

Intrathecal

epidural

Opioid Agonists: ADVERSE EFFECTS

- Respiratory depression

- Nausea/vomiting

- Orthostatic hypotension

- Excessive sedation

- Constipation

- Urinary retention

- Cough suppression

- Biliary colic

Opioid Agonists: CONTRAINDICATIONS

- Decreased respiratory reserve

- Kidney/liver disease

- Prostatic hypertrophy

- Head injury - ICP

- Hypersensitivity

- Pregnancy

- labor/delivery

Opioid Agonists: NURSING IMPLICATIONS

◦Antidote: naloxone (Narcan)

◦Black Box Warning: Do not use with other opioids, benzodiazepines, and other CNS depressants

◦Assess for AE

Principles of Opioid Administration

◦Morphine is FIRST CHOICE for severe pain

◦Morphine has no ceiling/meperidine (Demerol) has a ceiling

◦Preferred route: oral, PCA, epidural, transdermal

◦Autostop order 48-72 hours unless reordered

◦Physical dependence

◦A state in which an abstinence syndrome will occur if the drug is abruptly withdrawn

Abuse

◦Drug use that is inconsistent with medical or social norms

Addiction

◦Continued use of a psychoactive substance despite physical, psychologic or social harm

Withdrawal (physical dependence)

Yawning, rhinorrhea, sweating

Irritability, anorexia, tremor, "gooseflesh"

Violent sneezing

Weakness

Bone and muscle pain

Muscle spasms

Kicking movements

"kicking the habit"

N/V/D

Tolerance

◦Larger dose is required to produce the same response that could formerly be produced with a smaller dose.

◦Tolerance develops to analgesia, euphoria, sedation and respiratory depression.

◦Not to constipation nor miosis

Other Opioid Agonists

Fentanyl

- Sublimaze - parenteral

Anesthesia

Duragesic trans-dermal

◦Slow onset of action (24 h)

◦Lasts 3 days

◦Drug continues to be absorbed 24 h after patch removed

Transmucosal

- dangerous to non-users

◦Hydrocodone + acetaminophen: (Vicodan, Lortab)

◦Oxycodone (OxyContin)

◦In combination with: aspirin (Percodan), acetaminophen (Percocet)

◦Used for moderate to severe pain

other opioids

Codeine

Use: mild to moderate pain; Severe cough

Methadone

Used for detoxification & maintenance of addicts

Used for severe pain

Agonist-Antagonist

◦Available as nasal spray, IM, or IV

◦Use: moderate to severe pain

◦Obstetrical analgesia

◦Adjunct to general analgesia

Examples:

◦Examples:

◦Butorphanol (Stadol)

◦Pentazocine (Talwin)

◦Nalbuphine (Nubain)

◦Buprenorphine (Buprenex)

Centrally Acting Analgesics

- tramadol (Ultram) {analog of codeine}

- Moderately strong analgesic

◦dexmedetomidine (Precedex) {alpha 2 receptor agonist}

◦clonidine (Duraclon) {alpha 2 receptor agonist}

Opioid ANTAGONIST

NALOXONE

- Block and displace opiates from receptor sites specific to opioids

- May cause withdrawal symptoms in opioid- dependent people

◦Onset: within minutes of parenteral administration (almost immediately if IV)

◦T1/2: 30 to 81 minutes

◦Metabolized in liver

◦Excreted by kidneys

> Shorter duration of action than opioids

> Likely to need repeated injections

>Titrate with care to avoid acute withdrawal