Rectal absorption of lamotrigine compressed tablets

Epilepsia. 2000 Jul;41(7):850-3. doi: 10.1111/j.1528-1157.2000.tb00252.x.


Purpose: Interruption of oral drug administration poses a significant clinical problem for antiepileptic drugs that have no parenteral formulation. If a drug is absorbed rectally, rectal administration can be a useful alternative when the oral route of administration is not possible. The purpose of this study was to compare the single-dose pharmacokinetics of lamotrigine (LTG) compressed tablets after rectal and oral administration in healthy volunteers.

Methods: A single LTG compressed tablet (100 mg) was administered orally and rectally to 12 volunteers in this single-dose, two-period, crossover study with a 2-week washout between doses. For rectal administration, tablets were crushed and suspended in 10 mL of water. Plasma samples were collected from 0 to 120 hr after each dose and analyzed for LTG by an HPLC method developed for this investigation.

Results: LTG plasma concentrations were lower after rectal administration versus oral administration. The average area under the curve was 28.90 +/- 9.5 microg/mL/hr after rectal administration and 51.71 +/- 19.2 microg/mL/hr after oral administration. The average maximum LTG concentration was 0.53 +/- 0.14 microg/mL after rectal administration and 1.45 +/- 0.35 microg/mL after oral administration. The relative bioavailability for LTG compressed tablets was 0.63 +/- 0.33 for rectal administration. There were no drug-related rashes or serious side effects.

Conclusions: LTG suspension prepared from LTG compressed tablets is absorbed rectally, although not to the same extent or rate as when given orally.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Oral
  • Administration, Rectal
  • Anticonvulsants / administration & dosage*
  • Anticonvulsants / pharmacokinetics*
  • Area Under Curve
  • Biological Availability
  • Cross-Over Studies
  • Epilepsy / drug therapy*
  • Humans
  • Intestinal Absorption
  • Lamotrigine
  • Rectum / metabolism
  • Single-Blind Method
  • Triazines / administration & dosage*
  • Triazines / pharmacokinetics*


  • Anticonvulsants
  • Triazines
  • Lamotrigine