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PTD - 254

Test Directory - Lamotrigine



Clinical Indications

Lamotrigine is an anti-epileptic drug, used for treatment of partial and generalised tonic-clonic seizures. 

Drug Kinetics

Lamotrigine is rapidly and completely absorbed and maximum serum concentrations are reached approximately 3 hours after dosing. The drug is extensively metabolised by the liver and excreted in urine. In the first trimester of pregancy clearance is increased. Concomitant therapy may affect levels by inducing liver metabolism (phenytoin and phenobarbitone) or reducing clearance (valproate).

Request Form

Combined Pathology Blood form (Yellow/Black)


Analysed by the Toxicology Laboraotry, Llandough Hospital, Wales, if specific criteria met.

Specific Criteria

Most evidence shows that plasma monitoring is unnecessary in the majority of patients on lamotrigine therapy. Monitoring may be useful in helping with  dosing for patients on multiple therapy or in establishing compliance.

Increasing clearance during pregnancy is pronounced and can result in break-through seizures. Regular monitoring of lamotrigine concentrations is recommended during pregnancy.

Patient Preparation

Samples should be collected before next dose (trough)

Turnaround Time

2 weeks




1 ml


Pink/purple top (EDTA) tube


For paediatrics a red top (EDTA) tube is required.

Causes for Rejection

Not meeting specific criteria for analysis.

Target range


Up to 15 mg/L

Target  Range

Patients on monotherapy with intractable epilepsy may require up to 15 mg/L to achieve adequate control, levels >15 mg/L do not improve seizure control and may give rise to toxicity)


Rashes (3-5% patients), weakness, visual disturbances, drowsiness, dizziness,  unsteadiness, irritability, nausea and G.I. disturbances. Side effects may be seen in some patients with levels above 15 mg/L.

Lab. Handling

Processing: Aliquot and store plasma at 4C in separating fridge (CB39). Referral: LAMO and send or BPRO and save at -20C in separating freezer (CB40)

Version 1.1 / July 2015                                                                              Approved by: Consultant Biochemist