1, Backgrounds and Aims
	The capsaicin 8 % is an adhesive patch containing a high concentration (8%) of synthetic capsaicin, a selective agonist of the transient receptor potential vanilloid 1 channel.
	A systematic review and meta-analysis published by Finnerup et al. recommends capsaicin 8 % as second line treatment for peripheral neuropathic pain. Capsaicin has a verified analgesic effect in post herpetic neuralgia, diabetic neuropathy, surgical neuropathy and other cases of peripheral neuropathic pain.
	Trigeminal neuralgia (TN) is one of the most common neuropathic pains found in the head and neck. It is manifested as shock or burning crises in undefined intervals, and is typically triggered by non-painful stimulation in the face (allodynia). 
	Different mechanisms are involved in the onset and maintenance of neuropathic pain both at peripheral and central levels.
	We report two cases of trigeminal neuralgia, idiopathic and post-herpetic, treated with capsaicin 8 % patch
2.Methods
* Case 1
	A 44-year-old woman diagnosed with idiopatic trigeminal neuralgia consulted for intense allodynia, hyperalgesia to cold and wind (VAS 9) that prevented her leaving home. Examination revealed pinprick hyperalgesia. She was being with carbamazepine, amitriptyline, baclofen and delayed onset tramadol. 
	She refused Gasser blockade, so we decided to place a capsaicin 8% patch. At the onset of treatment, she presented severe burning sensation (VAS 8) and moderate erythema. When the patch was withdrawn, the patient reported a reduction in allodynia from 9 to 6.
	One month after the patient reported reduction of the area of pain by 20 %, and reduction of the number of episodes of lancinating paroxysms. The improvement lasted for 16 weeks.
	New treatment with capsaicin 8 % patch was decided for the patient’s residual neuralgia. After this second application pain intensity reported was VAS 3, and duration of the analgesic effect was 24 weeks. The reduction of the pain area was >75 % on the affected side. In this review the patient reported new pain symptoms, considered as trigeminal “mirror-image” neuralgia that includes the V2 and V3 branch on the contralateral side.
Figure 1 shows a gradual reduction of the pain area with successive applications; 
Figure 2 shows the “mirror-image” pain area.
Case 2
	A 63-year-old man diagnosed with acute herpes zoster (HZ) in the first branch of the left trigeminal nerve with clinical course of less than one month, visited the pain unit. The patient reported onset of severe, burning pain for more than six days with a lancinating component, VAS 10, which had been increasing since onset. 
 
	Two months after starting treatment with amitriptyline, gabapentin and delayed tramadol at maximum doses, the patient came for review and continued to report continuous pain in the area of the first branch of the left trigeminal nerve, VAS 7, with a significant burning sensation. The lancinating aspect disappeared, but  he reported severe allodynia and pinprick hyperalgesia as intensity 9 (VAS). A sympathetic blockade of the stellate ganglion was prescribed but was not effective. He was offered treatment with Capsaicin.
 
	Capsaicin 8% patch was applied for 60 minutes in the area of pain with ocular protection. One week from treatment we observed a reduction of the pain area; minimal allodynia remained on the left ciliary region (VAS1).
 
	A new patch was applied 3 months after the first because of increased pain (VAS 5) and allodynia (VAS 3). One week from the placement a significant reduction in pain intensity and allodynia was again observed (VAS 1).
 
	In last  review, the patient reported mild discomfort (VAS 1) free of allodynia with amitriptyline. Treatment was discontinued due to the patient´s lack of pain.
Figure 3 shows the reduction of the pain area after initial application.

Results
Capsaicin 8% patch has been successfully used for treatment of symptoms of peripheral neuropathic pain either alone or in association with other analgesics.9
 
The existence of cold and and pinprick hyperalgesia correlates with the response to the patch10,11 as occurs in the two case studies reported.
 
Repeated treatments have had similar efficacy in our patients, which coincides with results from other studies2.
 
Efficacy was greater in patient 2, in which the patch was applied two months from the onset of pain symptoms. Maihofner et al.12 published greater efficacy of capsaicin 8% patch in those patients with less clinical course, when treatment commenced before six months from onset of pain.
 
In both cases concomitant medication (antidepressants, anticonvulsants and opioids) could be reduced; part of the medication could even be discontinued in the latter case. Wagner et al.13 In a retrospective analysis, patients treated with capsaicin found that more than 50% can discontinue oral treatment.
Conclusion
These findings suggest that in those patients with trigeminal neuralgia experiencing cold and pinprick hyperalgesia, the early initiation of topical treatment might be indicated. The limitations of this study are based on the lack of comparison of the effectiveness of the patch with other patients with this same diagnosis but without hyperalgesia. The findings warrant further investigation with a larger number of patients in prospective trials.

CAPSAICIN 8% PATCH IN TRIGEMINAL NEURALGIA: CASE REPORTS