Drugs Used in Pain Management
Pharmacologic options for pain management range from simple analgesics, such as acetaminophen or low-dose nonsteroidal anti-inflammatory agents (NSAIDs) for the relief of mild to moderate chronic pain, to opioids for more severe pain (Table 1).
Simple Analgesics: Acetaminophen is useful for the relief of mild to moderate osteoarthritic pain in scheduled, divided doses not exceeding 4 g/day.NSAIDs may also be used in appropriate doses, for short periods of time. COX-2 inhibitors may be less likely to be associated with gastrointestinal bleeding and may be administered once daily, reducing nursing time for medication administration or the likelihood of missed doses. All NSAIDs should be given with a meal to avoid gastrointestinal upset. Periodic monitoring of renal function and blood count should be performed.
Topical Analgesics: Topical analgesics may also be used in the management of chronic pain. Capsaicin cream, derived from red peppers, desensitizes nerve fibers associated with pain by depleting substance P. Regular applications of the cream, beginning with the 0.025% concentration and progressing to the 0.075% formulation, may be helpful in relieving pain. Patients generally report a warming sensation at the site of application. The cream should not be used on broken or irritated skin. Several weeks of therapy may be necessary to determine efficacy. Menthol or methylsalicylate-containing products in the form of liniments, creams, sprays and other formulations may also be effective in relieving joint pain. Topical anesthetics, such as lidocaine ointment or gel, and combination anesthetic ointments or creams may also be of benefit in relieving joint pain or pain in other localized sites.
Pharmacologic Management of Pain
Tramadol: Tramadol has been successful in managing pain in patients over the age of 75 years who are unable or unwilling to use opioids at doses of 300 mg or less per day. Doses in renally impaired patients (those with a creatinine clearance [CrCl] of 30 mL/min or less) should be further reduced by decreasing the dosing interval to every 12 hours and a maximum dosage of 200 mg/day. Dosage adjustment is also necessary in patients with hepatic impairment. Tramadol should not be used with opioids, tricyclic anti-depressants, or selective serotonin reuptake inhibitors. Patients taking other medications that lower the seizure threshold or who are at high risk for seizures may experience seizures with the addition of tramadol. Concomitant use of carbamazepine significantly lowers the bioavailability of tramadol, requiring a dose increase. In clinical studies with a majority of patients over the age of 65 years, dizziness, nausea, and vertigo were the most common side effects, reported in up to 46% of patients receiving tramadol for as long as three months.
Tricyclic Antidepressants: Tricyclic antidepressants have been successfully used in managing pain in combination with analgesic agents, particularly for neuropathic pain syndromes. Initiation of therapy at low doses (1025 mg of nortriptyline) given at bedtime will avoid daytime drowsiness and improve sleep. Limited data exist for the efficacy of the selective serotonin reuptake inhibitors as adjunct pain management, precluding their routine substitution for tricyclic agents.
Anticonvulsants: With relatively few drug interactions in comparison to other anticonvulsants, gabapentin has been shown to be effective as adjunct pain therapy in patients with neuropathic pain. Gabapentin was shown to be as effective as amitriptyline in the management of diabetic peripheral neuropathy. In order to avoid the most common side effect, drowsiness, therapy is initiated at relatively small doses of 100 mg in the evening, with gradual upward titration every five to seven days. In patients with impaired renal function (CrCl>60 mL/min), doses should not exceed 1200 mg/day in divided doses.A maximum dose of 600 mg/day in divided doses is recommended in patients with CrCl 3060 mL/min. Monitoring of drug serum levels is not indicated with gabapentin.
Narcotic Analgesics: Multiple narcotic analgesics are available as single agents or in combination with other analgesics for the relief of moderate to severe pain. Sustained-release preparations, such as morphine sulfate sustained-release tablets, offer the benefit of once or twice a day administration with continuous pain relief. Short-acting, immediate release formulations should be readily available to the patient for breakthrough episodes of pain. Use of the short-acting agents serves as a method of titration for the sustained-release preparations and as a measure of their efficacy. The timing of the use of immediate-release medications on a prn basis can help determine if pain control is diminished at the end of the dosing interval or if specific times of the day require an increased dose of analgesic. The inclusion of acetamin-ophen or ibuprofen with narcotic analgesics limits their usefulness. Acetaminophen-associated hepatotoxicity and ibuprofen-associated renal and gastrointestinal toxicities limit the total daily dose of the combination products. With gradual dose titration based on patient response, there is no dose limitation with single-agent narcotic analgesics. Oxycodone controlled-release tablets or other narcotic analgesics may be alternatives in patients unable to tolerate morphine sulfate, as intolerance of one agent does not prevent the trial of other narcotic analgesics.
Nonpharmacologic Interventions: Nonpharmacologic interventions have been used, often in conjunction with analgesic or adjunct medications, as part of a comprehensive pain management program (Table 2). Specific modalities may be used alone or in combination, depending on the patient’s condition.
As part of an interdisciplinary team, the pharmacist should ascertain whether all of the patient’s pain needs are being met during or after physical therapy sessions. Patients may refuse therapy sessions because they perceive the sessions as causing pain, or pain exists prior to the therapy visit. Premedication with a relatively rapid onset analgesic one-half to one hour prior to the therapy appointment can significantly reduce discomfort and allow the rehabilitation process to proceed smoothly. Medication after the therapy session can be useful in relieving discomfort or aching experienced by the patient.
Patients may also experience pain during wound care. Routine premedication for dressing changes in patients with a Stage III or IV pressure ulcer or other serious wound is recommended and can reduce the discomfort or pain associated with manipulation of the affected area.
Nonpharmacologic Treatment of Pain