Intrathecal morphine after C-section may reactivate herpes. (Lesions Reactivated in 38% of 50 Women).

HILTON HEAD, S.C. - In women with a history of herpes simplex labialis, intrathecally administered morphine given postoperatively after C-section significantly increases the risk of reactivating the infection, compared with patient-administrated analgesia, according to the results of a prospective, randomized study.

But that doesn't mean that patient-controlled analgesia (PCA) is preferable, given the associated risks of respiratory depression in the mother and nursing newborn, Dr. Kelly Shannon said at the annual meeting of the Society for Obstetric Anesthesia and Perinatology.

The association between epidural morphine for post Csection analgesia and reactivation of herpes simplex labialis (HSL) is well established, but the effects of intrathecally administered morphine on reactivation have not been studied, said Dr. Shannon of Magee-Women's Hospital, Pittsburgh.

In his study, 100 women with HSL with a history of lesions recurring at the same site were randomly assigned to receive either intrathecal or patient-controlled morphine for analgesia after scheduled elective cesarean section. Patients were followed for 3 days in the hospital and for 30 days afterward by telephone to determine if any lesions had emerged or if there had been any adverse outcomes.

Serum IgG herpes simplex virus (HSV) titers were measured, and oral HSV cultures were done using tissue culture before and after surgery The groups were similar in terms of their mean antibody titers.

In the intrathecal group, 19 out of 50 (38%) patients developed reactivation lesions, compared with 8 of 48(16%) women in the PCA group, a difference that was statistically significant. In 92% of the reactivation cases, the lesions recurred at the original site.

Although it's not clear why the intrathecal route would increase the risk of reactivation, the theory is that it allows some morphine to act on receptors at the "itch" center of the medulla, which is close to the trigeminal nerve, where most latent HSV ...