Chronic neurogenic facial pain: lack of response to intravenous phentolamine.

AIMS: Chronic neurogenic facial pain is commonly resistant to treatment and is often the source of significant patient morbidity. Adrenergic mechanisms are postulated to play a role in producing this type of pain, and adrenergic blocking agents are frequently used in clinical practice for pain control therapy. The analgesic effectiveness of an adrenergic blocking agent, intravenous phentolamine, was compared to saline and intravenous lidocaine in the present study using a single-blind protocol in patients with chronic neurogenic facial pain. METHODS: Thirty patients were studied whose common clinical features included pain for more than 6 months, unilateral trigeminal distribution, constant dysesthesia, and no evidence of pathology or known etiology. Phentolamine (30 mg), lidocaine (100 mg), and saline were each infused over periods of 5 to 10 minutes. Pain ratings were assessed every 4 minutes throughout each study period using a 10-point pain intensity scale. RESULTS: No patient reported subjective improvement of pain during or immediately following phentolamine or saline infusions alone. Sixteen of the 30 patients reported decreased pain following lidocaine infusion. In the majority of the patients, the duration of lidocaine analgesia was less than 30 minutes; however, some patients reported decreased pain for a longer time. CONCLUSION: The results do not support an adrenergic mechanism for chronic neurogenic facial pain. The response to lidocaine, a nonadrenergic, membrane-stabilizing agent, suggests that it may have clinical effectiveness in certain neurogenic facial pain patients.