It is typically used in doses of 30 to 120mg daily, with lower doses preferred in patients who are concerned about side effects. Duloxetine should be avoided in patients with hepatic or severe renal insufficiency. Venlafaxine is used in doses of 75-225mg daily for the treatment of acute and chronic neuropathic pain. 111,129 SNRIs are contraindicated in patients taking MAOIs within the previous two weeks due to the risk of serotonin syndrome, and in some cases, hypertensive crisis. Duloxetine has moderately potent inhibitory effects on the hepatic cytochrome P450 enzyme CYP2D6, resulting in drug interactions with other medications that affect or are affected by this enzyme. Side effects associated with SNRIs include 136 : ● Nausea, which appears to diminish over time ● Dizziness ● Diaphoresis ● Increased blood pressure, due to the effects on norepinephrine ● Headaches ● Sexual dysfunction ● Increased risk of bleeding ● Hyponatremia While tricyclic antidepressants do not carry FDA approval for pain management, they are used frequently for a number of chronic pain states. Amitriptyline is the most widely studied TCA in chronic pain and is the only TCA with proven efficacy in migraine prevention. When used for pain, amitriptyline can be started at 25mg at bedtime, and slowly increased at weekly intervals up to 125mg daily. Nortriptyline is also used for chronic pain and may be preferred due to its reduced anticholinergic and sedative effects when compared to amitriptyline. Nortriptyline can be started at 10mg daily at bedtime and increased weekly in 10 to 25mg intervals up to 75 to 150mg daily. TCAs should be started at low doses, and doses should only be increased slowly as needed. Low starting doses are particularly important when using TCAs in older adults, who are at a higher risk of being negatively affected by side effects. 129 Since TCAs are sedating, administration with barbiturates, alcohol or other agents with CNS depressant effects can cause oversedation, impaired Pharmacologic Treatment of Pain: Opioids Historically, prescribers limited the use of opioids solely to patients with acute or cancer-related pain. Over time, the use of opioids to treat many types of pain has increased to dangerously high levels. Prescription rates of opioids had been steadily rising since the advent of new opioid products in the 1990s, and prescription rates peaked in 2012 with more than 255 million prescriptions for opioids written that year. Opioid prescribing rates have been slowly declining since 2012, with approximately 142 million opioid prescriptions written in 2020. 138 Declines in opioid prescribing are likely attributed to regulatory restrictions, more stringent clinical practice guidelines, education, and reimbursement controls. However, the opioid epidemic is a major public health crisis that is affecting Americans at alarming rates. 29
functioning, and falls. Medications that increase serotonin levels, including herbal preparations such as St. John’s wort and SAM-e, can lead to serotonin syndrome when co-administered. Agents that cause QT prolongation, such as certain broad-spectrum antibiotics, should be used with caution with cyclic antidepressants, due to additive risk. Other agents that lower the seizure threshold, such as tramadol, can increase the risk of seizures when administered with cyclic antidepressants. Side effects associated with cyclic antidepressants include 137 : ● Overdose: as little as 10 times the daily dose of cyclic antidepressants can be fatal, due to QT prolongation causing fatal arrhythmias ● Cardiac side effects, such as orthostatic hypotension, QT prolongation, tachycardia and arrhythmias ● Lower seizure threshold ● Bone fractures ● Anticholinergic effects due to muscarinic receptor blockage, including dry mouth, blurred vision, constipation, urinary retention, confusion, and delirium ● Antihistaminic effects due to histamine receptor blockage, including sedation, increased appetite causing weight gain, confusion and delirium ● Sexual dysfunction ● Diaphoresis ● Tremor ● Topical Lidocaine Data supporting the use of topical lidocaine is limited, though it is used frequently in the treatment of chronic pain. It is considered an adjuvant agent in the treatment of neuropathic pain, with the best evidence supporting its use in postherpetic neuralgia and diabetic neuropathy. 129 Lidocaine 5% patches are commonly used; a single patch contains 700mg of lidocaine. Up to three patches can be applied at a time for up to 12 hours in a 24-hour period; a 12-hour patch-free period is required each day due to the risk of lidocaine toxicity. Systemic absorption with lidocaine patches is low, averaging 3%, but this requires cautious use in patients with renal, hepatic, or cardiac dysfunction. 129 According to a report from the Substance Abuse and Mental Health Services Administration (SAMHSA), approximately 9.5 million people misused opioids in 2020. Of those users, 9.3 million participated in the recreational use of prescription painkillers. 139 An estimated 70,000 Americans died from opioid overdose in 2019. 138 Patient-provider agreements Agreements between the patient and provider define the roles and responsibilities of the provider and patient when starting opioid therapy. They are used as a means to educate the patient on best practices for opioid use and can serve as a tool to identify concerns as the patient continues utilizing opioid therapy. Components of an effective patient-provider agreement include 140 :
Book Code: CA23CME
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