Notes
Distributed by Generic Health Pty Ltd
Boxed Warnings
Severe, potentially life‐threatening rashes have been reported in association with the use of lamotrigine, particularly in children. Accordingly, lamotrigine should be discontinued at the first sign of rash unless the rash is clearly not drug‐related (see Section 4.2 Dose and Method of Administration).
1 Name of Medicine
Lamotrigine.
2 Qualitative and Quantitative Composition
Lamotrigine GH tablets containing 25 mg, 50 mg, 100 mg or 200 mg lamotrigine.
List of excipients with known effect. Sugars as lactose.
For the full list of excipients, see Section 6.1 List of Excipients.
3 Pharmaceutical Form
Lamotrigine GH 25 mg tablets are uncoated white, circular, flat bevelled tablets, with '25' debossed on one side and a central breakline on the other side.
Lamotrigine GH 50 mg tablets are uncoated white, circular, flat bevelled tablets, with '50' debossed on one side and a central breakline on the other side.
Lamotrigine GH 100 mg tablets are uncoated white, circular, flat bevelled tablets, with '100' debossed on one side and a central breakline on the other side.
Lamotrigine GH 200 mg tablets are uncoated white, capsule-shaped, biconvex tablets with '200' debossed on one side and plain on the other side.
4 Clinical Particulars
4.9 Overdose
Symptoms and signs. Overdose has resulted in the following clinical features: nystagmus, ataxia, dizziness, somnolence, blurred vision, headache, vomiting, impaired consciousness, grand mal convulsion and coma. QRS broadening (intraventricular conduction delay) has also been observed in overdose patients. Acute ingestion of doses in excess of 10 to 30 times the maximum therapeutic dose of lamotrigine have been reported. Overdoses involving quantities 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 lamotrigine 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 activated 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 as clinically indicated. Measures should be taken to protect the airway as consciousness may be impaired.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).
5 Pharmacological Properties
5.3 Preclinical Safety Data
Genotoxicity. Lamotrigine was not genotoxic in assays for gene mutation or chromosomal damage.
Carcinogenicity. There was no evidence of carcinogenicity following daily oral administration of lamotrigine to mice and rats for up to two years at doses of up to 30 and 10 mg/kg respectively.
Effect of lamotrigine on cardiac rhythm and conduction. In vitro studies show that lamotrigine exhibits Class IB antiarrhythmic activity at therapeutically relevant concentrations (See Section 4.4 Special Warnings and Precautions for Use). It inhibits human cardiac sodium channels with rapid onset and offset kinetics and strong voltage dependence, consistent with other Class IB antiarrhythmic agents. Lamotrigine did not slow ventricular conduction (widen QRS) in healthy individuals in a thorough QT study; however, it could slow ventricular conduction and increase the risk of arrhythmia in people with structural heart disease or myocardial ischemia. Elevated heart rates could also increase the risk of ventricular conduction slowing with lamotrigine.
6 Pharmaceutical Particulars
6.7 Physicochemical Properties
Lamotrigine is a substituted asymmetric triazine. It is a white to pale cream-coloured powder. It is slightly soluble in ethanol and chloroform, and very slightly soluble in water. The pKa of lamotrigine at 25°C is 5.7.
Chemical structure.
https://stagingapi.mims.com/au/public/v2/images/fullchemgif/CSLAMOTR.gif Chemical Name: 3,5‐diamino‐6‐(2,3‐dichlorophenyl)‐1,2,4‐triazine.
Molecular Formula: C9H7Cl2N5.
Molecular Weight: 256.1.
CAS number. 84057-84-1.
7 Medicine Schedule (Poisons Standard)
(S4) Prescription Only Medicine.
Summary Table of Changes
https://stagingapi.mims.com/au/public/v2/images/fulltablegif/LAMOGHST.gif