For patients with herpetic-related neuralgia, clinical characteristics and features of infection may be used to identify patients at a higher risk for medication-resistant pain (MRP), according to results of a retrospective study published in Pain and Therapy.

The objective of the study was to evaluate the association between clinical characteristics and medication responsiveness, which can help identify patients at risk for inadequate pain management.

A total of 213 patients aged older than 50 years with herpes zoster-related persistent pain (score of >5 points on a 10-point visual analog scale [VAS]) were enrolled at the Shenzhen Nanshan People’s Hospital and the 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzen, China, between 2017 and 2020. Patients were prescribed gabapentin at a dose of 100 to 300 mg 3 times per day that was increased to a maximum dosage of 3600 mg/day; pregabalin at 75 to 150 mg/day, increased to a maximum dosage of 600 mg 1 to 3 times/day; and amitriptyline at 10 mg/day, increased to a maximum dosage of 50 mg/day. Two weeks after treatment, the researchers used VAS to assess pain symptoms.


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Among patients receiving standard pain therapy, 38.03% (n=81) were classified as treatment-sensitive and achieved satisfactory pain relief (defined as reduction in VAS >3), 61.97% (n=132) were classified as treatment-resistant and needed adjusted therapeutic strategies (such as nerve block, pulsed radiofrequency, and stimulation of the spinal cord).

In a univariate analysis, MRP was associated with older age, male sex, severe lesions, postherpetic neuralgia, anxiety, and later-phase disease (all P <.05).

In a multivariate analysis, independent predictors of subacute vs acute herpes zoster (odds ratio [OR], 8.95; 95% CI, 3.15-29.48; P =.0001), severe lesions (OR, 3.84; 95% CI, 1.44-10.81; P =.0084), and symptoms of depression (OR, 1.10; 95% CI, 1.00-1.20; P =.0447) remained significantly associated with MRP. High blood pressure was associated with decreased risk for MRP (OR, 0.36; 95% CI, 0.14-0.87; P =.0266).

Using the clinical characteristics of disease phase, diabetes, lesion, location, depression, family history, hypertension, McGill score, VAS, and anxiety, the best-fit support vector machines model predicted MRP with a receiver operating characteristic area under the curve (AUC) of 0.918 (95% CI, 0.819-1.018; P <.001).

“The phase of diseases, degree of skin lesion, and depression are independent risk factors, whereas hypertension is a potential protective factor for developing analgesic resistance among patients with herpetic-related neuralgia,” the researchers concluded, but cautioned that the findings may not be generalizable to a younger patient population.

Reference

Zhou J, Sun W, Liu Y, et al. Clinical characteristics, treatment effectiveness, and predictors of response to pharmacotherapeutic interventions among patients with herpetic-related neuralgia: A retrospective analysis. Pain Ther. Published online September 12, 2021. doi:10.1007/s40122-021-00303-7