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Australian Journal of Pharmacy : March 2005
Add-on Therapy in Children under 2 years: To ensure a therapeutic dose is maintained the weight of a child must be monitored and the dose reviewed as weight changes occur. If the doses calculated for children, according to bodyweight, do not equate to whole tablets the dose to be administered is that equal to the lower number of whole tablets. Due to the very limited safety, efficacy, pharmacokinetic and dosing data that are available in children under 2 years old, dosing in this age group should only be initiated within a specialist unit. There are no data avail- able on the use of lamotrigine in neonates. In particular the use of lamot- rigine in patient less than 2 years old, who are also taking sodium valproate, is not recommended. This is due to the difficulties in provid- ing an accurate initial dose. Because of a risk of rash, the initial dose and subsequent dose escalation should not be exceeded (see Precautions). General Dosing Considerations for Add-on Therapy: For patients receiv- ing lamotrigine in combination with other antiepileptic drugs, whether or not optimal dosing has been achieved, a re-evaluation of all antiepileptic drugs in the regimen should be considered if a change or no improvement in seizure control or an appearance or worsening of adverse experiences is observed (see Precautions). Withdrawal of Concomitant Antiepileptic Drugs: The dose of lamot- rigine following the withdrawal of concomitant antiepileptic drugs will be dependent upon the pharmacokinetics of the drugs(s) being withdrawn, together with the overall clinical response of the patient. The withdrawal of enzyme inducing antiepileptic drugs (egphenytoin and carbamazepine) may not require a reduction in the lamotrigine dose unless there is a need due to safety considerations. An increase in the lamotrigine dose may, however, be required following the with- drawal of enzyme inhibiting antiepileptic drugs (eg sodium valproate) (see Precautions and Drug Interactions). Discontinuation of lamotrigine in patients with epilepsy: As with other antiepileptic drugs, abrupt withdrawal of lamotrigine may provoke rebound seizures and should be avoided wherever possible. Unless safety concerns (for example serious skin reactions) require an abrupt with- drawal, the dose of lamotrigine should be gradually decreased over a period of two weeks. General Dosing Recommendations: Women taking hormonal contraceptives: (a) Starting lamotrigine in patients already taking hormonal contraceptives: Although an oral contraceptive has been shown to increase the clearance of lamotrigine (see Precautions and Interactions), no adjustments to the recommended dose escalation guidelines for lamotrigine should be necessary solely based on the use of hormonal contraceptives. Dose escalation should follow the recom- mended guidelines based on whether lamotrigine is added to an enzyme inhibitor of lamotrigine e.g. valproate; whether lamotrigine is added to an enzyme inducer of lamotrigine e.g. carbamazepine, phenytoin, phenobarbital, primidone or rifampin; or whether lamot- rigine is added in the absence of valproate, carbamazepine, pheny- toin, phenobarbital, primidone or rifampicin. (b) Starting hormonal contraceptives in patients already taking maintenance doses of lamotrigine and NOT taking enzyme inducers of lamotrigine: The maintenance dose of lamotrigine may need to be increased by as much as two-fold according to the individual clinical response. (See Precautions and Interactions) (c) Stopping hormonal contraceptives in patients already taking maintenance doses of lamotrigine and NOT taking enzyme inducers of lamotrigine: The maintenance dose of lamotrigine may need to be decreased by as much as 50% according to the individual clinical response. (See Precautions and Interactions) AUSTRALIAN PRESCRIPTION PRODUCTS GUIDE SUPPLEMENT The Elderly: To date, there is no evidence to suggest that the response of this age group differs from that in young patients with epilepsy. The dosage schedule recommended in adults and children more than 12 years of age can be applied to the elderly population (aged 65 years or more). As older patients are more likely to suffer from intercurrent illness and require medications to treat other medical conditions, lamotrigine should be used cautiously in these patients and they should be monitored regularly. Hepatic Impairment: Initial, escalation and maintenance doses should generally be reduced by approximately 50% in patients with moderate (Child-Pugh grade B) and 75% in severe (Child-Pugh grade C) hepatic impairment. Escalation and maintenance doses should be adjusted accordingly to clinical response. Renal impairment: Caution should be exercised when administering lamotrigine to patients with renal failure. For patients with end-stage renal failure, initial doses of lamotrigine should be based on patients’ AED regimen; reduced maintenance doses may be effective for patients with significant renal functional impairment. Administration: All Elmendos Tablets, which have been formulated as dispersible/chewable tablets, may be swallowed whole, chewed or dispersed in a small volume of water (at least enough to cover the whole tablet). Overdosage: Symptoms and signs: Overdose has resulted in the following clinical features: nystagmus, ataxia, dizziness, somnolence, blurred vision, headache, vomiting, impaired consciousness, increased seizures and coma. Acute ingestion of doses in excess of 10 to 30 times the maxi- mum therapeutic dose has been reported. Overdoses involving quan- tities up to 15 g have been reported for lamotrigine, some of which have been fatal. A patient who ingested a dose calculated to be between 4 and 5 g lamot- rigine was admitted to hospital with coma lasting 8 - 12 hours, followed by recovery over the next 2 - 3 days. A further patient who ingested 5.6 g lamotrigine was found unconscious. Following treatment with acti- vated charcoal for suspected intoxication the patient recovered after sleeping for 16 hours. Treatment: No specific antidotes are available to treat overdosage. In the event of overdosage, the patient should be admitted to hospital and given appropriate supportive therapy. Measures should be taken to protect the airway as consciousness may be impaired. Pack: Elmendos Dispersible/Chewable tablets 25mg, 50mg, 100mg and 200mg are white to off-white, multifaceted super elliptical unscored tablets with an odour of blackcurrant. The 25mg tablet is marked “GSCL5” on one side and “25” on the other side, the 50mg tablet is marked “GSCX7” on one side and “50” on the other side, the 100mg tablet is marked “GSCL7” on one side and “100” on the other side, and the 200mg tablet is marked “GSEC5” on one side and “200” on the other side. All presentations of Elmendos tablets are available in packs of 56 tablets. Elmendos 25mg: AUST R 98073 Elmendos 50mg: AUST R 98074 Elmendos 100mg: AUST R 98075 Elmendos 200mg: AUST R 98076 Storage: All Elmendos tablets should be stored below 30°C. All of the tablets should also be kept in a position where they will remain dry and Elmendos Dispersible/Chewable tablets 25mg, 50mg, 100mg and 200mg should be protected from light. All States and A.C.T—S.4. Approval by the TGA: 11 November 2003 Safety Related Notification: 28 September 2004 Date of Amendment: 25 October 2004 Issue 3 THE AUSTRALIAN JOURNAL OF PHARMACY VOL.86 MARCH 2005 ? IBC