Ultrasound-Mediated Transdermal Medication May Relieve Zoster-Associated Allodynia

By Reuters Staff

July 07, 2020

NEW YORK (Reuters Health) - Ultrasound-mediated transdermal lidocaine and capsaicin appears to relieve pain and emotional distress related to allodynia caused by herpes zoster, researchers in China report.

Current local treatments for zoster-associated allodynia include intradermal injection with lidocaine or external application of lidocaine or capsaicin cream to the affected area. These treatments can be painful and might not be sufficiently effective.

Ultrasound-mediated transdermal drug delivery has been shown to provide pain relief in patients with chronic low-back muscle strain or inflammatory pain.

Dr. Yun-Xia Zuo of West China Hospital, Sichuan University, in Chengdu, and colleagues evaluated the efficacy of ultrasound-mediated transdermal lidocaine and capsaicin delivery versus intradermal injection of lidocaine in an unblinded pilot trial of 60 patients with severe allodynia caused by herpes zoster.

All patients received basic treatment with oral gabapentin, mecobalamin, and amitriptyline. Patients randomly assigned to receive ultrasound were treated for 30 minutes daily, while patients in the intradermal group received daily injections of lidocaine, and patients in the control group received only the basic treatment.

Mean visual analog scores (VAS) for allodynia decreased from 8.1 at baseline to 2.1 the day after the first ultrasound treatment and declined further to 0.5 on day 7, the researchers report in Pain Medicine.

In the intradermal group, the mean VAS for allodynia decreased from 8.2 at baseline to 3.4 the day after treatment and to 0.5 on day 7. The average VAS score decreased from 8.2 at baseline to 4.4 on day 4 in the control group and remained almost unchanged during follow-up.

The overall VAS scores for allodynia were significantly lower after treatment in the two treatment arms than in the control arm.

The mean emotional VAS (on the scale of 0 = best mood and feeling to 10 = worst mood and feeling) improved from 6.8 at baseline to 1.6 the day after treatment and to 0.6 by day 7 in the ultrasound group.

In the intradermal group, the mean emotional VAS improved from 7.1 to 3.4 to 1.9, respectively. In the control group, the mean emotional VAS improved from 6.7 at baseline to 3.4 the day after treatment and remained almost unchanged thereafter.

The average gabapentin consumption over the seven-day treatment period was 5,700 mg in the ultrasound group, 6,000 mg in the intradermal group, and 8,000 mg in the control group.

The incidence of adverse events (dizziness, nausea, vomiting and drowsiness) was significantly higher in the control group than in the ultrasound and intradermal groups.

Almost all participants in the intradermal group reported having intense pain during intradermal blockade which was sufficient to cause two patients to withdraw from the study.

The study had no commercial funding, and the authors report no conflicts of interest.

Dr. Zuo did not respond to a request for comments.

SOURCE: https://bit.ly/3dklNvU Pain Medicine, online June 10, 2020.