Muscle spasms: an unexpected adverse drug reaction of pemetrexed?

In this report we describe a 53-year-old woman with advanced non-small cell lung cancer, treated with pemetrexed and cisplatin combination therapy, followed by pemetrexed monotherapy. The patient developed severe muscle spasms at least twice, shortly after administration of pemetrexed monotherapy. A possible explanation for this observation is that in combination with cisplatin therapy, the patient was hyperhydrated before administration to promote renal excretion and reduce toxicity. Pemetrexed is also renally excreted, which supports the finding that toxicity did not occur when the patient was hyperhydrated. After discontinuation of pemetrexed the symptoms did not reoccur. All aspects of this case point to a possible relationship between pemetrexed and an adverse drug reaction (ADR). We conclude that muscle spasms are a rare, but possibly dose-related ADR of pemetrexed-based therapy.