Lamotrigine dosage

Lamotrigine is effective for the maintenance treatment of bipolar disorder. It is more effective for depression relapse prevention than for mania relapse. Its primary limitation as an acute treatment is the time required for titration to an effective dosage. In addition to maintenance monotherapy, it is sometimes used in combination with lithium or divalproex, although combination with divalproex increases the risk of rash, and lamotrigine dosage adjustment is required.37... 

A 9-year-old girl with Lennox-Gastaut syndrome, who had initially had an improvement in seizure frequency, insidiously developed myoclonic status epilepticus after the lamotrigine dosage was increased from 15 to 20 mg/kg (24). Withdrawal of lamotrigine resulted in rapid disappearance of status. 

Stevens-Johnson syndrome, and 3 as suggestive of Stevens-Johnson syndrome two deaths were reported. Rashes associated with one or more symptoms of hypersensitivity reactions occurred in 19 children. Of 29 patients with Stevens-Johnson syndrome, toxic epidermal necrolysis, or hypersensitivity reactions, for whom precise details were available, 83% were taking lamotrigine with concomitant valproate and 85% were taking lamotrigine dosages higher than recommended. 

The case report also raises the possibility of an interaction between lamotrigine and isoniazid. If isoniazid is added to or withdrawn from lamotrigine treatment, be alert for the need to adjust the lamotrigine dosage. 

However, note that if they are also taking valproate in addition to phenytoin, the lamotrigine dose should be reduced, see Lamotrigine + Vd-proate , below. The lamotrigine dosage may need to be reduced if phenytoin is withdrawn. 

When carbamazepine is administered with primidone, decreased primidone levels and higher carbamazepine serum levels may result. Cimetidine administered with carbamazepine may result in an increase in plasma levels of carbamazepine that can lead to toxicity. Blood levels of lamotrigine increase when the agent is administered with valproic acid, requiring a lower dosage of lamotrigine... 

The most frequent side effects are diplopia, drowsiness, ataxia, and headache. Rashes are usually mild to moderate, but Stevens-Johnson reaction has also occurred. The incidence of the more serious rashes appears to be increased in patients who are also receiving valproic acid and who have rapid dosage titration. Valproic acid substantially inhibits the metabolism of lamotrigine. 

Conversion from adjunctive therapy with valproate to monotherapy with lamotrigine Achieve a dosage of 200 mg/day of lamotrigine according the guidelines. While... 

Dosage regimen for bipolar disorder The target dose of lamotrigine is 200 mg/day (100 mg/day in combination with valproate and 400 mg/day in combination with carbamazepine or other enzyme-inducing drugs). Doses above 200 mg/day are not recommended. 

Dosage adjustment for bipolar disorder If other drugs are subsequently introduced, the dose of lamotrigine may need to be adjusted. In particular, the introduction of... 

Coadministration with other hormonal contraceptive preparations or hormone replacement therapy Although the effect of other hormonal contraceptive preparations or replacement therapy on the pharmacokinetics of lamotrigine has not been evaluated, the effect may be similar to oral contraceptives. Therefore, similar adjustments to the dosage of lamotrigine may be needed. 

Nonteratogenic effects - There have been reports of decreased lamotrigine concentrations during pregnancy and restoration of prepartum concentrations after delivery. Dosage adjustments may be necessary to maintain clinical response. 

Serious rashes associated with hospitalization and discontinuation of lamotrigine have been reported. It is recommended that lamotrigine not be restarted in patients who discontinued use due to rash associated with prior treatment with lamotrigine unless the potential benefits clearly outweigh the risks. If the decision is made to restart a patient who has discontinued lamotrigine, assess the need to restart with the initial dosing recommendations (See Administration and Dosage). 

In normal dosages juvenile myoclonic epilepsy may be induced with lamotrigine. 

In 103 children with cranial diabetes insipidus, 3 children who started or had an increase in dose of lamotrigine needed a larger dose of desmopressin, suggesting an effect on the renal tubule or on drug clearance (76). Lamotrigine also increased desmopressin dosage requirements in two other children with cranial diabetes insipidus (78). 

A 26-year-old woman with bipolar I disorder took lithium and valproate, and sometimes additional risperidone and lamotrigine. Both risperidone and lamo-trigine produced dermatological adverse effects. Her serum lithium concentration was 0.82 mmol/1. Topiramate 75 mg/day was added. A week later, she continued to show a mixed state with mostly manic features and a raised lithium concentration of 1.24 mmol/1. The lithium concentration continued to increase over the next 4 days to 1.97 mmol/1 even though the lithium dosage was reduced from 900 to 750 mg/day. Lithium was withdrawn and the lithium concentration fell. Lithium was then restarted at half the admission dose to achieve a blood concentration of 0.67 mmol/1. Subsequent increases in the dose of topiramate resulted in further increases in the lithium concentration. 

Reduce lamotrigine dose or stop dosage increase... 

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