Effect of barbiturate on central pain: difference between intravenous administration and oral administration.

OBJECTIVE

To examine whether the oral administration of barbiturates is of clinical use in a patient with central pain.

SETTING

Pain Clinic, Osaka University Medical Hospital, Osaka, Japan.

PATIENT: A patient with central pain after loss of his left upper extremity.

INTERVENTIONS: A 50-mg dose of intravenous amobarbital, which produced a plasma concentration of 2.5-4.0 microg/ml, was effective in reducing the central pain. Subsequently, doses of 300-400 mg/day were administered orally; these succeeded in achieving similar plasma concentration levels.

RESULTS AND

CONCLUSIONS

Oral administration of barbiturate did not alleviate central pain, even when the plasma concentration was the same as the effective level in intravenous use. Pharmacokinetic and pharmacodynamic factors more complex than simple plasma concentrations may be involved in producing the difference in the effects.