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Abstract & Commentary
Source: Cheshire WP. Fosphenytoin: An intravenous option for the management of acute trigeminal neuralgia crisis. J Pain Symptom Manage 2001;21:506-510.
The author, a neurologist, reports three remarkable cases of immediate relief from severe trigeminal neuralgia pain with intravenous fosphenytoin. A 66-year-old woman with a 10-year history of recurrent paroxysmal left mandibular pain described as "sharp jabs or electrical shocks" was treated with 0.9 g (18 mg/kg) fosphenytoin as phenytoin equivalents (PE) for 20 minutes and received immediate relief. The patient remained pain-free for two days. Prior to this therapy, she had been on carbamazepine and had increased the dose to the point of toxicity without effect. Interestingly, she had no relief with oral phenytoin or gabapentin. Her surgery revealed indentation of the trigeminal nerve by vascular structures and the patient was pain-free after decompression. An 80-year-old man with a four-year history of paroxysmal, sharp, shooting, or burning right mandibular pain, triggered by touching the lower lip, speaking, chewing, drinking, or swallowing, received 1.0 g PE (11 mg/kg) fosphenytoin, given in 100-mg doses every 10 minutes with complete relief. This patient remained pain-free for about three days. He underwent successful trigeminal nerve compression with a percutaneous balloon. Finally, a 75-year-old woman with a 14-year history of paroxysmal, left lower facial pain described as "electricity," burning, or tingling, received 1.0 g PE (14 mg/kg) fosphenytoin with nearly complete relief. The next morning she was pain-free and remained so for two days. Oral phenytoin and a variety of other anticonvulsants failed to alleviate the recurrent pain and she underwent a successful Gasserian balloon compression.
Comment by Richard J. Hamilton, MD, FAAEM, ABMT
This is not a complex paper, but I found it a fascinating series. These patients are in the worst pain imaginable, and something that offers prompt relief like this truly is remarkable. A number of the trigeminal neuralgia patients I have seen are completely unresponsive to narcotics. While prior studies support the use of intravenous phenytoin, it is not considered as useful as fosphenytoin appears to be in this series. Fosphenytoin is a phosphate ester prodrug of phenytoin that is better tolerated parenterally and is inert until converted to phenytoin by endogenous esterase. A particular explanation is not offered for the efficacy of fosphenytoin, nor could I determine one by reviewing its mechanism of action. Please note that pain returned in all cases despite treatment with carbamazepine, gabapentin, baclofen and carbamazepine, or oral phenytoin. The patients all eventually required suboccipital craniectomy or balloon compression. I reviewed this article because I think it’s something that would make a real difference for a suffering patient. If you use it and have success, get in touch with me and we’ll start collecting the next case series to report!