Failure of absorption of baclofen after rectal administration

We wished to determine the degree to which baclofen was absorbed from an aqueous vehicle after rectal administration. A comparison was made to absorption after oral administration. After oral administration, the baclofen half-life was 2.3 to 3.4 hours and peak serum concentrations were achieved from 1 to 2.1 hours after administration. No measurable absorption was observed after rectal administration of the drug in any subject. Rectal administration of baclofen is not a clinically sound treatment option when oral administration of the drug is not possible. For patients receiving chronic baclofen therapy, other medications such as a benzodiazepine should be considered at times when oral administration of medication is not possible.