Opioids

An opioid is a chemical substance that has a morphine-like action in the body. Opiates activate receptors that modulate our perception of painful stimuli (nocioceptive pain). Opiates act within the brain and spinal cord to alter nociceptive transmission. There are three opioid receptors—μ, κ, and δ—but the primary analgesic effect is via the μ-receptor.

The scope of this book will focus on the seven main opiates used in clinical practice: Codeine, hydrocodone, oxycodone, morphine, Dilaudid (hydromorphone), fentanyl, and methadone. These are all direct agonists of the opioid receptor. Mixed opioid receptor agonist–antagonists such as Suboxone (buprenorphine and naloxone) are beyond the scope of this book.

When to use

Opioids can be first-line medications for acute pain (a dislocated shoulder, postsurgical pain, an acute fracture) and typically are second-line drugs for chronic pain (lumbar spondylosis, diabetic peripheral neuropathy, osteoarthritis). After an acute pain state resolves, the patient should be taken off opioids. For chronic pain conditions, typically physicians use adjuvant medications (nonopioid pain medications) at therapeutic doses first. It is important to try nonopioid pain medication at clinically therapeutic doses before resorting to opioids. For example, 30 mg of Cymbalta for diabetic peripheral neuropathy has not been shown to be effective, whereas 60 mg has. Interventional pain management procedures may be used as well (joint injections, sympathetic nerve blocks, epidural steroid injections) to alleviate pain and can be a good option before prescribing opioids.

How to use

Physicians often struggle with which opiate to prescribe. It is important to remember that all of the opioids in this chapter have a similar method of action; thus morphine is not better for one type of pain as compared to oxycodone. None is disease or location specific—one is not better for orthopedic pain, whereas another better for pelvic pain. It often comes down to prescriber preference and comfort. Appropriate strength and frequency are more important than the choice of opioid itself. This chapter will focus on using opioids in both hospital and outpatient settings. A simple algorithm for prescribing opioids is as follows Table 15-1.

Hospital Setting: Intravenous Opioids

When in the hospital setting, determine if the opioid needs to be given intravenously (IV). If the IV route is needed, you only have three choices—morphine, Dilaudid, or fentanyl—as they are the only three of the primary seven opioids available in a common IV form (Table 15-1). If the patient does not need IV narcotics, please skip to the next section. Opioids given via the IV route are reserved for hospital patients who have an acute flare of pain. They are also warranted for patients with chronic pain hospitalized for other reasons who need to be nothing per mouth (nil per os [NPO]). These patients cannot receive their usual oral pain medication.

All IV medications are short acting by definition. At equal analgesic doses, no one opioid is stronger than another and none is better than another unless the patient has an allergy to one in particular. The medication is given via an IV push or via a patient-controlled
analgesia ([PCA]; PCAs are covered in Chapter 16. Table 15-2 presents the equivalent doses for the three IV pain medications.

Table 15-1 The Seven Primary Opioids

Medication	Intravenous	Short Acting Form	Long Acting Form
Codeine		x
Hydrocodone		x
Oxycodone		x	x
Morphine	x	x	x
Dilaudid (hydomorphone)	x	x	x
Fentanyl	x		x
Methadone			x

A common order would be 2 mg of IV morphine to be given every 4 hours as needed, or Dilaudid IV 0.4 mg every 4 hours as needed. Fentanyl 25 μg IV every 4 hours as needed can be used as well, but most hospitals typically have morphine and Dilaudid on the floor rather than fentanyl. If a patient does not respond to these doses, rather than switching between the different IV pain medications, you should increase the dose of the opioid you are currently using. I have been paged by the resident to be told that a patient did not respond to IV Dilaudid and asked what opioid would I like to try next. Upon inquiry, I discovered that the patient received a dose of 0.2 mg of Dilaudid. In a case such as this, if the patient does not respond to 0.2 mg IV Dilaudid every 4 hours as needed, increasing the dose to 0.4 mg every 4 hours as needed may be effective. If that does not work, the next step is 1 mg of Dilaudid every 3 hours as needed rather than giving up on Dilaudid and switching to another opioid. Patients who are opioid tolerant usually require more significant starting doses than opioid-naïve patients—for example, an opioid-tolerant patient should start with Dilaudid 1 mg rather than 0.4 mg.

Toradol (ketorolac)—the only nonsteroidal anti-inflammatory drug (NSAID) that can be given intravenous—is commonly used in combination with IV opioids. NSAIDs work by blocking inflammation at the site of pathology and by altering pain perception in the central nervous system (CNS). Toradol blocks inflammatory prostaglandins that sensitize nerve endings to the action of bradykinin, histamine, and other inflammatory factors, making them more likely to transmit pain. In a postoperative study, patients treated with Toradol IV at fixed intermittent boluses required 26% less morphine than the morphine-alone group. Because of its potency, Toradol is limited to 5 days of use. Typically prescribe this medication as 30 mg IV or intramuscular (IM) every 6 hours or every 6 hours as needed. It should be used with caution in patients with a history of gastrointestinal or renal disease. I will often add Toradol to the IV opioid I am using to lower the total amount of opioid needed to control the pain to enable better control of side effects, which include constipation, nausea, and pruritus.

Intravenous opioids are stronger than their oral counterparts. IV morphine is three times stronger than oral morphine; thus giving 5 mg of IV morphine is equivalent to 15 mg of oral morphine. IV Dilaudid is five times stronger than oral Dilaudid; thus giving 2 mg of IV Dilaudid is equivalent to 10 mg of oral Dilaudid. Caution should be taken when converting from IV to oral opioid medication and vice versa.

Hospital or Outpatient Setting

Determine whether the patient has an acute pain condition that will completely resolve, a chronic pain condition that does not require continuous narcotics or a chronic pain condition that needs continuous narcotic treatment.

Acute pain conditions are dynamic with large fluctuations of pain levels over time, even within 1 day. Short-acting oral pain
medications are needed to match the quickly oscillating pain state. Short-acting oral pain medications have a quick onset and quick offset of action, lasting 4 to 6 hours. Of the seven primary opioids, there are five available in a short-acting oral form: Codeine, hydrocodone, oxycodone, Dilaudid, and morphine (Table 15-3). Again, none is disease specific. Methadone and fentanyl do not come in a short-acting oral form. Per the mission of this book, prescribing short-acting oral opioids will be broken down to the clinically most relevant pain states.

Table 15-2 Equal Analgesic Doses of Intravenous Pain Medications

Medication	Equivalent Dose	Starting Dose	Onset Time	Duration
Morphine	10 mg	2–3 mg	5–10 mins	3–5 h
Dilaudid	1.5 mg	0.2–0.4 mg	5–20 mins	3–4 h
Fentanyl	100 μg	25 g	Less than 1 min	1–2 h

Table 15-3 Short-acting Oral Opioids and Pain Levels for Which They are Most Useful

Level of Pain	Medication
Less severe pain	Codeine
Moderate to severe pain	Hydrocodone (hydrocodone + Tylenol = Vicodin) Oxycodone (Oxycodone + Tylenol = Percocet)
Severe pain	Morphine Dilaudid (hydromorphone)

Short-acting Oral Opioid Medication Choices

For Less Severe Pain: Codeine

Tylenol with codeine (Tylenol 3) is typically prescribed. Tylenol 3 contains 30 mg of codeine and 300 mg of Tylenol (acetaminophen). It can be prescribed to take up to four times a day. Tylenol 3 may also be used for moderately severe pain in patients who cannot tolerate stronger opioids, for example, the elderly.

For Moderate to Severe Pain: Oxycodone or Hydrocodone

Oxycodone or hydrocodone is typically prescribed. Both of these medications are available as 5-, 7.5-, or 10-mg tablets. Typically a physician prescribes one tablet every 4 to 6 hours as needed. The 5-mg tablet is considered standard strength, the 7.5-mg tablet extra strength, and the 10-mg tablet extra-extra strength. Both oxycodone and hydrocodone usually come wrapped in a Tylenol coating. When oxycodone is wrapped in a Tylenol coating, it is know as Percocet (Fig. 15-1). When hydrocodone is wrapped in a Tylenol coating, it is known as Vicodin (Fig. 15-1). The standard Tylenol coating of Percocet and Vicodin is 325 mg. Thus if you prescribe Percocet 7.5/325 you are prescribing 7.5 mg of oxycodone wrapped in 325 mg of Tylenol. When you prescribe Vicodin 5/325 you are prescribing 5 mg of hydrocodone wrapped in 325 mg of Tylenol.

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