Results of a Mayo Clinic study suggest that the addition of topical 2% amitriptyline / 0.5% ketamine gel to the usual multimodal therapy can help reduce both the pruritus and the pain associated with shingles.
In their case study, John R. Griffin, M.D., and Mark D.P. Davis, M.D., of the Mayo Clinic’s department of dermatology, note that while acute herpetic pain has been found to significantly affect health-related quality of life, no studies have attempted to measure the quality-of-life impact of herpetic pruritus. They also note that many drugs that alleviate neuropathic pain do not necessarily have the same effect on neuropathic itch in the individual patient.
The case study focuses on a 64-year-old man with Crohn’s disease who was admitted for enterocutaneous fistula takedown. He had no history of herpes zoster. During his postoperative stay, he had hyperalgesia, erythema, and vesicles with ipsilateral conjunctivitis and keratitis. He was treated with intravenous acyclovir. Varicella zoster virus was confirmed with polymerase chain reaction of blister fluid.
Three days after the skin eruption, the patient reported itching in the area, a symptom that in two weeks became unrelenting severe pruritus and burning pain that the patient rated as 10/10 on the visual analog scale. Over three days, the pruritus extended to include the bilateral scalp, though the pain remained localized to the area of infection. Initial treatment recommendations included wound care with dilute acetic acid wet dressings and twice daily 2.5% hydrocortisone cream. The patient reported that he had a decrease in his symptoms that lasted several hours with this regimen. Oral gabapentin therapy was begun at a dosage of 300mg three times daily and was titrated to up to 400mg three times daily.
Low-dose oral opioid therapy was discontinued in favor of non-opioid analgesics, as opioids may cause considerable pruritus in some patients. Topical lidocaine patches were applied to intact surrounding skin every 12 hours. Therapy with oral hydroxyzine (25 mg daily) was started, but was used intermittently because of the patient’s concern about associated somnolence. After the combination of these interventions, the patient rated his itch at 7/10 or 8/10 for most of the day and 10/10 for the rest of the day.
Though the patient’s primary medical and surgical conditions had stabilized by this time, his pruritus and pain prohibited his dismissal. Treatment of conjunctivitis and keratitis consisted initially of erythromycin ophthalmic ointment. Unfortunately, he also had an immune stromal keratitis, which required the addition of ophthalmic corticosteroids.