Nonopioid drugs can be used in the treatment of many nociceptive and neuropathic pain conditions. For severe pain, especially severe chronic cancer pain, use of opioids may be necessary. Noninvasive nonpharmacologic treatments, including physical and psychological therapies, have been shown to improve pain and function in patients with some common chronic pain conditions and are unlikely to cause serious harms. A multimodal approach to analgesic therapy can increase pain control while reducing opioid use and adverse effects.

A lidocaine 1.8% patch (ZTlido – Scilex) has been approved by the FDA for treatment of pain associated with postherpetic neuralgia (PHN). A lidocaine 5% patch (Lidoderm, and generics) was approved earlier for the same indication and has been used off-label for treatment of other types of localized pain. Both of these patches are available only by prescription. Lidocaine 4% patches (Aspercreme, IcyHot, and others) are available over the counter for back, neck, shoulder, and joint pain.

The FDA has approved an adjuvanted, recombinant varicella zoster virus (VZV) vaccine (Shingrix – GSK) for prevention of herpes zoster (shingles) in adults ≥50 years old. Shingrix is the second herpes zoster vaccine to be approved in the US; Zostavax, a live-attenuated VZV vaccine approved for the same indication, has been available since 2006.

Treatment of epilepsy should begin with a single antiepileptic drug (AED), increasing its dosage gradually until seizures are controlled or adverse effects become intolerable. If seizures persist, specialists generally recommend trying at least one and sometimes a second alternative drug as monotherapy before considering use of two drugs concurrently. When used for the appropriate seizure type, AEDs are roughly equivalent in efficacy. Drug choice is usually based on factors such as ease of use, adverse effects, drug interactions, presence of comorbidities, and cost.

Pain can be acute or chronic. The two major types of chronic pain are nociceptive pain and neuropathic pain. Nociceptive pain can be treated with nonopioid analgesics or opioids. Neuropathic pain is less responsive to opioids and is often treated with adjuvant drugs such as antidepressants and antiepileptics. Combining different types of analgesics may provide an additive analgesic effect without increasing adverse effects.

A new once-daily formulation of gabapentin (Gralise – Depomed) has been approved by the FDA for treatment of postherpetic neuralgia (PHN). Immediate-release (IR) gabapentin (Neurontin, and others), which has been available in the US since 1994, is also approved for this indication, but is taken three times a day. Extended-release gabapentin enacarbil (Horizant) was recently approved by the FDA for treatment of restless legs syndrome.

The FDA has approved a topical 8% patch formulation of capsaicin (Qutenza – NeurogesX), available only by prescription, for local treatment of postherpetic neuralgia. Postherpetic neuralgia occurs after herpes zoster in about one third of patients ≥60 years old and can persist for months or even years.

The 2006 Medical Letter article on the then-new varicella-zoster vaccine concluded that Zostavax appears to be safe and effective in protecting patients ≥60 years old against herpes zoster and postherpetic neuralgia, especially in reducing the severity and duration of the disease.1 Some new information has recently become available.

CLINICAL STUDIES — A Veterans Administration randomized, double-blind trial enrolled more than 38,000 patients ≥60 years old and followed them for a mean of 3.4 years after administration of Zostavax or placebo. Since the efficacy of the vaccine had been demonstrated previously (51% in preventing zoster and 67% in preventing postherpetic neuralgia), the objective of this study was to examine its safety. Transient varicella-like rash occurred at the inoculation site in 0.11% of vaccine recipients and in 0.04% of patients who received a placebo injection. Erythema, swelling, pain and tenderness at the injection site were more frequent and more severe with the vaccine than with placebo. There were no other significant differences. Serious adverse events occurred in 1.4% of patients in each group.2

USE — Despite its efficacy and the frequency and morbidity of herpes zoster, this vaccine is hardly used. One study in 2007 found that only 2% of patients ≥60 years old had received it.3 A 2008 survey found that 7% of potential recipients had been vaccinated.4 A study of the reasons for such sparse usage concluded that the expense ($194 wholesale), the need for a freezer to store the vaccine (a vaccine that can be kept in a refrigerator is available in Europe), and reimbursement through Medicare Part D, which generally provides pharmacy benefits, rather than Part B, which physicians are more familiar with, were contributing factors.5

CONCLUSION — The efficacy of the herpes zoster vaccine (Zostavax) was well established before the FDA approved it in 2006. Several years’ use has now provided more data supporting the safety of the vaccine. It deserves wider use.

1. Herpes zoster vaccine (Zostavax). Med Lett Drugs Ther 2006; 48:73.
2. MS Simberkoff et al. Safety of herpes zoster vaccine in the shingles prevention study. Ann Intern Med 2010; 152:545.
3. PJ Lu et al. Herpes zoster vaccination among adults aged 60 years or older in the United States, 2007: uptake of the first new vaccine to target seniors. Vaccine 2009; 27:882.
4. JS Schiller and GL Euler. Vaccination coverage estimates from the National Health Interview Survey: United States, 2008. Atlanta: Centers for Disease Control and Prevention 2009. Accessed at www.cdc.gov/nchs/data/hestat/vaccine_coverage/vaccine_coverage.pdf on 12 May 2010.
5. LP Hurley et al. Barriers to the use of herpes zoster vaccine. Ann Intern Med 2010; 152:555.

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Pain can be acute or chronic. Chronic pain has been broadly classified into two types: nociceptive and neuropathic. Nociceptive pain can be treated with nonopioid analgesics or opioids. Neuropathic pain is less responsive to opioids; adjuvant medicines such as antidepressants and anticonvulsants are often used to treat neuropathic pain. Combining different types of analgesics may provide an additive analgesic effect without increasing adverse effects.

Pregabalin (Lyrica - Pfizer), a structural analog of gamma-aminobutyric acid (GABA) similar to gabapentin (Neurontin - Pfizer, and others), which recently became available generically, has been approved by the FDA for treatment of neuropathic pain associated with postherpetic neuralgia (PHN) and diabetic peripheral neuropathy (DPN), and for adjunctive treatment of partial onset seizures in adults with epilepsy.

Three types of analgesic drugs are available: non-opioids, including aspirin, other nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen; opioids; and adjuvant drugs that are not usually thought of as analgesics, such as antidepressants, which can act as adjuvants when given with NSAIDs or opioids, or have analgesic activity of their own in some types of pain. Combining two different types of analgesics may provide an additive analgesic effect without necessarily increasing adverse effects.

Gabapentin (Neurontin - Pfizer), which has been available in the US since 1994, is approved by the FDA only for treatment of partial epilepsy and postherpetic neuralgia, but is widely used off-label for a number of other indications, especially neuropathic pain syndromes. According to one report, among Medicaid recipients in Florida receiving gabapentin, 71% of prescriptions were for chronic pain and 8% for seizures and neuralgia ("The Pink Sheet" February 2, 2004; 66:30).