We report on the case of a 52-year-old man who presented with a history of chronic
neuropathic pain treated with intrathecal application of morphine for many years. In
spite of significant dose escalation, considerable pain relief had not been achieved.
Ziconotide had been tried but not only did it not provide pain relief, but it also
caused severe side effects in this patient. A combination of morphine and clonidine
was delivered by a programmable pump, slowly increasing the clonidine rate over
several weeks. For ease of transition and minimization of hospitalization, which was
a special concern to this patient, combining clonidine and morphine was chosen over
monotherapy with hydromorphone, with both possibilities being described as equal
alternatives in the literature. Considerable pain relief was achieved during week 2
at a clonidine dose of 0.040 mg/d, thereby decreasing the visual analog score (VAS)
from 10 to 4. Yet, after developing erectile dysfunction and relative hypotension soon
after beginning clonidine treatment, the patient decided not to continue with the
combined application of morphine and clonidine. Treatment was therefore switched
back to the former monotherapy with morphine. Thereafter, erectile dysfunction
disappeared and blood pressure returned to habitual high levels. Although common
in systemic application, erectile dysfunction caused by the intrathecal application of
clonidine has not been described yet in the literature. In this patient, this rare side
effect decisively impaired life quality, subjectively outweighing the considerable pain
relief which could be achieved after formerly inefficacious treatment. Further and
prospective investigation might be needed to estimate the connection of erectile
dysfunction to intrathecal application of clonidine.
Key words: intrathecal, erectile dysfunction, morphine, chronic pain, drug pump