At an Internal Medicine 2009 session on managing pain in the hospitalized patient, Eva H. Chittenden, FACP, advised attendees about the “pain gap” that exists in clinical practice.
The main goals of pain treatment should be to reduce pain to a level that's tolerable for the patient, decrease suffering, maximize function and minimize adverse outcomes, Dr. Chittenden said. Although she acknowledged that there are other ways to treat pain, such as massage, physical therapy and acupuncture, her talk focused on use of medications.
For mild pain, use acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), Dr. Chittenden advised. Clinicians should avoid administering more than 4 grams of acetaminophen in 24 hours because of risk for hepatic toxicity, she noted. Also, acetaminophen should be used with extra care in patients with hepatic disease or heavy alcohol use. As for NSAIDs, although they work well for inflammatory and bone pain, they also have the highest incidence of adverse effects, including gastropathy, renal insufficiency, and inhibition of platelet aggregation, Dr. Chittenden said.
Opioids are the heavy hitters in pain management because they're effective against most types of pain. “You can prescribe [opioids] very safely if you have the knowledge and skill to do it,” Dr. Chittenden said. She cautioned attendees not to be afraid of high doses when administering opioids, which can be titrated up until symptoms improve or side effects become unacceptable.
“Sometimes, in some of our patients with advanced cancer, for example, the doses can get very high. I'm now comfortable with that, but many clinicians look at the doses and cannot believe how much somebody is on,” she said.
Because opioids conjugate in the liver and are excreted by the kidneys, clinicians should alter the drug, dosage, or schedule for patients in whom either system is impaired. In patients with renal failure, Dr. Chittenden noted, fentanyl and methadone are better choices than morphine; in those with liver damage, “start low, go slow,” she said.
Although methadone is gaining popularity for treatment of chronic pain, it should always be used with caution, Dr. Chittenden said. Its long half-life means that it takes longer for a patient to achieve a steady state, and it carries a higher risk for respiratory depression.
“Methadone is a drug I have tremendous respect for. It has its place, but it also has its downsides,” she said.
Dr. Chittenden offered the following advice for starting opioids in an opioid-naïve patient.
Provide round-the-clock dosing. This rule applies unless the patient has mild or infrequent pain. Start with short-acting opioids and dose every four hours.
“Many people make the mistake of dosing every four to six hours if it's PRN, and the nurse gives it to the patient every six to be conservative. The half-life is four hours, so you really want to give it every four hours,” Dr. Chittenden said.
Titrate doses daily depending on type of pain. For a patient with mild to moderate pain, the dose can be increased by 25% to 50%, whereas a patient with severe pain may need an increase of 50% to 100%. Dose adjustments can also be based on the total dosage of the breakthrough dose, Dr. Chittenden said.
Counsel patients on side effects. Patients should know to expect transient side effects such as fatigue, sedation, nausea and pruritis as well as permanent side effects like constipation. All patients on opioids should be prescribed a bowel regimen, Dr. Chittenden noted.
Always provide rescue medication for breakthrough pain. Each dose should be 5% to 15% of the total 24-hour dose and should be offered when the peak plasma concentration is reached. Breakthrough pain doses will need to be increased as the standing dose is increased, to 10% of the total 24-hour dose.
Convert to long-acting medications whenever possible. They improve compliance, Dr. Chittenden said. Doses should be adjusted every two to four days, she noted, and physicians should continue to provide short-acting breakthrough meds. It's important not to crush the long-acting medications, and you shouldn't start with a fentanyl patch in an opioid-naïve patient, she said.
Account for incomplete cross-tolerance when changing from one opioid to another. Reduce the equianalgesic dose by 25% to 50%, less if the patient's pain is uncontrolled and more if it's not or if the patient is experiencing adverse effects. Physicians should also know how to use the equianalgesic chart, Dr. Chittenden stressed (see box) .
“You can get into trouble if you don't use it,” she said. “You can always use one of those opioid calculators, but I've at times felt that they don't calculate the dose accurately, so it's good to be able to do the math yourself.”
Respiratory depression, addiction happen rarely
Inducing respiratory depression is a common worry for physicians prescribing opioids, but it's actually very uncommon, Dr. Chittenden said, especially if the drugs are used appropriately.
“One thing to know is that if your patient is awake and the nurse is calling you because they think the person has respiratory depression, that's not possible. You have to first have depressed consciousness; that precedes the respiratory depression,” she said.
In cases where respiratory depression does occur, it can be reversed by gradual administration of naloxone. Dr. Chittenden recommended diluting 1 ampule with normal saline to a total volume of 10 mL and giving 1 mL intravenously every minute until the patient responds. If the patient doesn't respond after 2 ampules of naloxone, it's time to start thinking about other causes for the respiratory depression, Dr. Chittenden said. “They should respond—they will respond—to the naloxone.”
While physicians prescribing opioids may be concerned about causing addiction, it's extremely rare in patients with advanced cancer, Dr. Chittenden noted. Much more common is pseudoaddiction, or behavior that looks like addiction but is due to undertreatment of pain. Patients with pseudoaddiction may exhibit what appears to be drug-seeking behavior because they're doing everything possible to get pain relief, Dr. Chittenden said.
“It's something to think about when people are pushing our buttons, when we feel like they're asking for too much. Are we adequately treating their pain?” she said. “We have to be savvy, but we also have to offer our patients the benefit of the doubt.”