Eight Common Pain Medications

An important intervention nurses regularly perform is administering pain medication. In this lesson, you’ll learn some key things to know about eight commonly used pain medications. To hear this on audio along with real-world examples, listen here.

The analgesic ladder

The analgesic ladder was proposed by the World Health Organization in 1986 as a way to improve the management of cancer-related pain. Since then it has been updated and is utilized to guide pain management for a broader range of both acute and chronic conditions.

The updated analgesic ladder consists of four steps:

• Step 1 (mild pain): Non-opioid analgesics such as acetaminophen and NSAIDS. May add adjuvants as needed.
• Step 2 (moderate pain): Weak opioids such as tramadol, hydrocodone or codeine. May add non-opioid pain medication and/or adjuvants as needed.
• Step 3 (severe pain): Strong opioids such as morphine, oxycodone, fentanyl, hydromorphone, and methadone. May add non-opioid and/or adjuvants as needed.
• Step 4 (if pain persists): Invasive and minimally-invasive non-pharmacologic interventions (such as surgery).

Critics of the ladder state that it does not take into account individual differences in medication response or pain tolerance. In addition, the reliance on opioids for moderate pain is considered short-sighted in that it doesn’t take into account the risks associated with these types of medications. However, the ladder does remain useful for understanding a step-wise approach to pain management, though experts suggest more research is needed in this area.

Non-opioid medications

When we think of pain management, we tend to think of opioid medications. However, there are many non-opioid options available that carry less risks for the patient such as respiratory depression, overdose, and long-term dependence. Three common ones are acetaminophen, ketorolac, and gabapentin.

Acetaminophen

Acetaminophen is a non-opioid analgesic used to treat mild to moderate pain as well as fever. It is also commonly used along with opioid medication to treat severe pain. Acetaminophen is available in PO, IV, and PR formulations. 

Oral and rectal acetaminophen reach peak concentrations within 30 to 60 minutes, while the IV form begins to take effect almost immediately. 

Important things to know about acetaminophen:

• It is used cautiously in individuals with mild liver impairment (and not at all in those with liver failure). 
• The maximum daily dose in adults is 3 to 4 grams and no single dose should exceed 1 gram. 
• Acetaminophen overdose can result in severe liver damage and liver failure.

Ketorolac

Ketorolac (Ex: Toradol) is a non-steroidal anti-inflammatory drug (NSAID) that is most commonly used to treat moderate to severe pain after a surgical procedure. It is available in oral, IV, IM, or nasal spray formulations. In the clinical setting you will most typically see it administered IV and is especially effective when utilized along with opioids, which has been shown to reduce opioid use postoperatively.

A typical adult dose of IV ketorolac is 30 mg every six hours, and should not exceed 120 mg in a 24 hour period. 

Important things to know about ketorolac:

• It is not to be used in those at high risk for bleeding or with current active bleeding. 
• Ketorolac is used cautiously or not at all in individuals with renal impairment as it can negatively impact the kidneys and lead to increased fluid retention.
• Ketorolac can cause GI bleeding, especially with use that persists over several days. For this reason it is contraindicated in individuals with active peptic ulcer disease or active GI bleeding and use is limited to no more than five days. 
• Ketorolac has also been shown to increase the risk for anastomotic leaks in colorectal surgery so is not generally used after these types of surgeries.

Gabapentin 

Gabapentin is a commonly used adjuvant medication which is especially effective in treating neuropathic pain. It is a CNS depressant that is classified not only as an analgesic but also as an anticonvulsant and mood stabilizer. 

Important things to know about gabapentin:

• Gabapentin can cause drowsiness, confusion, dizziness, and ataxia.
• If your patient is also taking another medication that depresses the CNS (such as opioids or even an antihistamine), they will be at higher risk for CNS depression when taking gabapentin.
• Different formulations of gabapentin are utilized for different things. The brand names utilized to treat neuropathic pain are Gralise and Neurontin.

Opioid medications

An important concept to understand when administering opioids is that of equianalgesic dosing. The equianalgesic dosing chart shows how the potency of various opioids compare to morphine, which is used as a baseline. For example, the dosing chart shows that 4 mg morphine is equivalent to 40 mcg fentanyl. Even if you knew nothing else about fentanyl, you can easily see this medication is much, much more potent than morphine.

With opioid medications you must always keep in mind they put the patient at high risk for oversedation and respiratory depression, especially when other CNS depressants are utilized such as benzodiazepines. If your patient receives too much opioid medication, the reversal agent is naloxone. In addition, opioids are not generally utilized (or are used with caution) in patients taking MAOIs due to the risk for additive effects leading to respiratory depression and the potential for serotonin syndrome. 

In addition to sedation and respiratory depression, other common adverse effects include nausea, pruritus, hypotension and constipation. 

• Nausea can be prevented by giving PO opioids with food. If unable to eat, ondansetron is a commonly utilized anti-nausea medication.
• Pruritus is often addressed with diphenhydramine, though this can compound sedation.
• To prevent dangerously low BP, avoid administering opioids to hypotensive patients.
• Opioid-induced constipation can be mitigated with adequate hydration, increased activity, and stool softeners such as docusate sodium (Colace).

Hydrocodone/Acetaminophen

The combination of hydrocodone and acetaminophen is commonly utilized in the clinical setting (ex: Norco). This PO medication is used for moderate to moderately-severe pain and comes in two common strengths based on the hydrocodone dose (5 mg and 10 mg).

Important things to know about hydrocodone/acetaminophen:

• Hepatotoxicity can occur with overdose due to the presence of acetaminophen, so always ensure you are calculating all sources of acetaminophen in a 24-hour period.
• Other brand names include Vicodin and Lortab
• The dose is written as 5-325 or 10-325 (the first number represents the opioid and the second number represents acetaminophen).

Oxycodone

Oxycodone is another commonly utilized PO opioid medication. It is stronger than Norco and PO morphine and can be administered without regard to total acetaminophen dosing since it does not contain any acetaminophen. Compared to other immediate-release PO opioid medications, it can have a quicker onset of action and start taking effect within 10 minutes of administration. Oxycodone is indicated for moderate to severe pain and has a duration of three to six hours.

Important things to know about oxycodone: 

• Oxycodone comes in both immediate-release and extended-release formulations. Make sure you know which one your patient is taking to avoid accidental overdose.
• Since oxycodone is excreted by the kidneys, reduced dosing is indicated in patients with renal impairment.

Morphine 

Morphine is available in multiple formulations, though PO and IV administration are most common. Note that PO doses of morphine are larger than IV doses due to the way it is metabolized. For example, 30 mg morphine PO is equivalent to 10 mg morphine IV. Both formulations can last up to five hours. 

Important things to know about morphine:

• Morphine can have increased effects in patients with renal failure, putting them at higher risk for respiratory depression. For this reason smaller doses and longer intervals between doses may be used (or it may be avoided altogether in these patients.)
• Morphine is available in multiple formulations including PO, IV, sublingual, rectal, intrathecal, and epidural.
• Extended-release morphine has a duration of up to 24 hours, so make sure you recognize this formulation to prevent accidental overdose.

Hydromorphone

Hydromorphone is another opioid medication that comes in multiple formulations, though IV administration is the most commonly used in the clinical setting.

Important things to know about hydromorphone

• IV hydromorphone can have a duration of three to six hours, and takes about 10 to 15 minutes to begin having an analgesic effect and may not peak until about 20 minutes.
• Other routes of administration for hydromorphone include PO (immediate and extended release), rectal, SubQ, IM, and epidural.
• Reduced dosing is utilized in patients with hepatic or renal impairment.

Fentanyl

The most potent of all the opioids is fentanyl, which is available in IV, transdermal, and transmucosal formulations. In the clinical setting, IV administration is most common, though you are likely to see fentanyl patches utilized for severe chronic pain. 

Important things to know about fentanyl:

• IV fentanyl takes effect quickly (within 3 to 5 minutes) and resolves quickly with a duration of 30 to 60 minutes. This makes it highly effective in quickly treating acute pain such as post-operatively.
• Fentanyl is so potent that it is measured in micrograms. A common IV dose range for adults is 25 to 100 mcg.
• Transdermal fentanyl has a duration of 72 hours and it’s extremely important that you ensure your patient does not have more than one patch on at a time as overdose can easily occur.

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Last Updated on September 27, 2024 by Maureen Osuna, MSN, RN