Based on several cases we have come across at the MIC lately, this is a reminder that rashes are a common side-effect associated with lamotrigine, the risk of which may be increased if the recommended initial dose and subsequent dose escalation are exceeded.

 Additionally, these doses are influenced by the presence of concomitant drugs which may increase or decrease lamotrigine levels. Dosing according to the SAMF is as follows:

Adult dose

Recommended initial dose and subsequent dose escalation should not be exceeded.

Epilepsy: Monotherapy: Initially 25 mg daily for 2 weeks, then 50 mg daily for 2 weeks, thereafter increased by up to 50–100 mg every 1–2 weeks according to the response.Usual maintenance 100–200 mg/day as a single dose or 2 divided doses;up to 500 mg/day has been required. Add-on therapy with valproate: Initially 25 mg on alternate days for 2 weeks,then 25 mg daily for 2 weeks, after that increased by up to 25–50 mg every 1–2 weeks according to the response. Usual maintenance 100–200 mg/day as a single dose or 2 divided doses. Add-on therapy without valproate: Initially 50 mg daily for 2 weeks, then 50 mg twice daily for 2 weeks, after that increased by up to 100 mg every 1–2 weeks according to the response. Usual maintenance 200–400 mg/day in 2 divided doses.

Bipolar disorder: Monotherapy or adjunct to agents that do not interact with lamotrigine: week 1–2, 25 mg once daily; week 3–4, 50 mg/day (as single or 2 divided doses);week 5, 100 mg/day; week 6,target stabilisation dose 200 mg/day (range 100–400 mg/day). Add-on therapy with enzyme inhibitors, e.g. valproate: week 1–2,12.5 mg/day (25 mg on alternate days); week 3–4,25 mg once daily; week 5, 50 mg/day (as single or 2 divided doses); week 6, target stabilisation dose 100 mg/day (maximum 200 mg/day). Add-on therapy with enzyme inducers in patients not taking valproate: week 1–2, 50 mg once daily; week 3–4, 100 mg/day in 2 divided doses; week 5, 200 mg/day; week 6, target stabilisation dose 300 mg/day, increasing if necessary to 400 mg/day in week 7.

Access the SAMF here.