Morphine spinals and the evidence for safety

Abstract

Josef Wang first described the use of intrathecal morphine in 1977.¹ He injected 8 rats (weighing between 400–500 g) with 25 μg intrathecal morphine. The tail-flick response was monitored. He concluded that intrathecal morphine might become a predictable modality of pain relief. Yaksh followed on 2 years later with a study looking at the use of intrathecal morphine in parturition in rats and rabbits.² Gravid rats and rabbits had intrathecal catheters inserted. After the initiation of nest building, the rats were injected with 15, 45 and 100 μg of intrathecal morphine and the rabbits with 80 μg. Analgesia was tested in the rats with a hot plate as well as a tail flick test. In rabbits it was tested with a hot probe. The animals were well analgised and there was no difference compared to controls with the onset of delivery as well as the percentage of pups alive after 150 minutes. Alper in the editorial of the same journal in which Yaksh’s article was published described intrathecal morphine as “potentially revolutionary”.³ He also made mention of how Josef Wang was now looking at the use of intrathecal morphine for the treatment of intractable pain of inoperable cancer.⁴