Introduction to Analgesic Drugs

Analgesic drugs are a class of medications that reduce or eliminate pain, and some can also reduce fever. They work by interfering with how pain signals are sent to the brain.

There are many types of analgesic drugs, including opioids (morphine and codeine), NSAIDs (ibuprofen and aspirin), acetaminophen (Tylenol), and topical capsaicin cream (for temporary pain relief).

Each type of analgesic works differently — some can be taken orally, and others need to be injected or administered intravenously. Intravenous and intramuscular administration are faster acting, while oral medications will take longer to give relief.

One of many nursing responsibilities includes being able to identify the analgesic indications, their side effects, contraindications, how they work in the body, and their mechanisms of action.

Opioid Analgesics

Opioids are a type of analgesic used for severe pain. They bind to receptors in the brain and spinal cord, which cause changes in the perception of pain.

When these receptors become activated, they release neurotransmitters (chemicals that send signals from one nerve cell to another). This causes the body’s pain-sensing neurons to stop sending pain signals back to the brain.

It’s important to note that they’re not anti-inflammatory or antipyretic.

Short list of opioid drugs

• Morphine sulfate
• Hydromorphone
• Codeine
• Oxycontin
• Oxycodone
• Fentanyl

Adverse Effects

Low RR – respiratory depression

• Hold dose for RR below twelve.

Low BP – Hypotension “orthostatic Hypotension”

• If the client becomes dizzy or light-headed, assist them to a seated position. Do not let them get up unassisted.

Low Brain – CNS sedation

• When the client easily falls asleep when talking (unarousable).

Memory Trick

Opioids make clients act low and slow.

Fentanyl Pharmacology

Fentanyl is a potent synthetic opioid analgesic used to manage chronic and persistent pain, but not acute pain. It works by binding to opioid receptors in the brain and spinal cord, which helps relieve pain by blocking pain signals from the nerves to the brain.

As a nurse, you should be aware that fentanyl and other opioids can cause respiratory depression and apnea. So these medications should be used with caution, especially in elderly clients, clients with chronic obstructive pulmonary disease (COPD), hypoventilation syndromes, or sleep apnea.

Fentanyl is also highly addictive and necessitates proper oversight by health care providers.

Side effects of fentanyl include nausea and vomiting, dizziness, itching, dry mouth, sweating, and trouble sleeping.

NSAIDs Pharmacology

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most common analgesics used to treat pain, fever, and inflammation. They work by interfering with the production of prostaglandins, which are produced by the body as part of its inflammatory response to injury or disease. These prostaglandins are responsible for causing pain, swelling, and fever.

The most common side effects of NSAIDs are nausea, vomiting, diarrhea, and bleeding in the stomach.

Short List of NSAIDs

• Naproxen
• Salicylate acid
• Acetylsalicylic acid
• Ibuprofen
• Indomethacin
• Ketorolac

Memory Trick for NSAIDs Side Effects

Not the best for the body (kidneys, heart failure, asthma, GI, clots, etc.)
Sticky blood “clots” (increased risk for thrombosis)
Asthma worsening
Increased bleed risk
Dysfunctional kidneys (renal injury after long-term use, Creatinine over 1.3, urine output 30ml/hr or less)
Swelling heart CHF (heart failure and HTN worsening)

Acetaminophen Pharmacologic Class

Acetaminophen is a type of analgesic drug that is used to treat pain, fever, and inflammation. It works by decreasing the production of prostaglandins in the brain and spinal cord, which causes an increase in pain tolerance and a decrease in sensitivity to temperature.

It’s one of the most common over-the-counter drugs, and it’s generally considered safe for children when used correctly.

Unlike other analgesics like aspirin or ibuprofen, acetaminophen does not affect blood clotting or cause stomach bleeding. This makes it an ideal choice for people at risk for bleeding disorders or stomach ulcers (commonly caused by aspirin).

Acetaminophen can cause liver damage or failure if not taken as prescribed or appropriately.

Capsaicin Pharmacology

Capsaicin is a molecule found in peppers. It’s what’s responsible for the burning sensation that accompanies spicy foods.

Capsaicin is also used as a lipid-soluble compound, which means it can be absorbed into the skin through a topical application (cream). Once it enters the bloodstream, it has a variety of effects on different organs and systems in the body.

Capsaicin helps treat neuralgia, a particular kind of pain (shooting or burning pain in the nerves). Neuralgia is caused by nerves close to the skin’s surface, and could develop following a herpes zoster infection (shingles or postherpetic neuralgia).

Capsaicin is also used to reduce minor pain from rheumatoid arthritis or muscle sprains and strains.

It’s also important to note that capsaicin can be very irritating at high concentrations.

PCA Pumps

A patient-controlled analgesia (PCA) pump is a device that lets clients control their own pain medication. The pump comes with an attached computer, which measures the amount of drug that’s been administered and alerts when it’s time for more.

This means that clients can get as much or as little pain relief as they need without being interrupted by nurses or other health care professionals.

When clients need pain medication, they can push the PCA pump button, and it will deliver a set amount of pain medication. These pumps typically come with a lock feature that prevents clients from receiving over the prescribed amount of medication.

Nurses caring for clients on analgesic-filled PCA pumps should follow the health care provider’s (HCP) prescription when initiating the medication. The nurse should always monitor the client’s pain level, level of consciousness (LOC), and side effects of the medication. Only the client should press the button for a dose of medication on the “patient-controlled analgesia” PCA pump.

Analgesic Drugs (and Opioids) Conclusion

Analgesics are mainly used to treat pain and inflammation – and they function by preventing the brain from receiving pain signals.

The most popular analgesics used to relieve pain, fever, and inflammation are non-steroidal anti-inflammatory medications (NSAIDs). They function by hindering the body’s ability to create prostaglandins, which are involved in the body’s inflammatory response to injury or disease.

One type of analgesic used for severe pain is opioids. They attach to the spinal cord and brain receptors, altering how pain is perceived.

Acetaminophen is also used to alleviate pain, fever, and inflammation. It functions by lowering prostaglandin production in the brain and spinal cord, which results in an increase in pain tolerance and a decrease in temperature sensitivity.

Capsaicin is a lipid-soluble type of analgesic that can be applied topically and absorbed via the skin (cream). The body’s many organs and systems are affected in several ways after reaching the bloodstream.

Clients can manage their own pain medication using a patient-controlled analgesia (PCA) pump. The pump measures the amount of medication supplied and notifies nurses when the vial in the pump needs to be replaced.

Sources

https://my.clevelandclinic.org/health/drugs/21483-analgesics
https://www.ncbi.nlm.nih.gov/books/NBK459161/
https://medlineplus.gov/druginfo/meds/a681004.html
https://www.mayoclinic.org/drugs-supplements/capsaicin-topical-route/side-effects/drg-20062561?p=1