Tiagabine

Anti-epileptic agents that induce hepatic enzymes (such as phenytoin, carbamazepine, phenobarbital and primidone) enhance the metabolism of tiagabine. Consequently, patients taking enzyme-inducing drugs may require doses of tiagabine above the usual dose range.

Tiagabine is metabolised in the liver and since the pharmacokinetics of tiagabine in patients with mild to moderate impaired liver function is modified, the tiagabine dosage should be adjusted by reducing the individual doses and/or prolonging the dose intervals.

Animal experiments have not shown a teratogenic effect of tiagabine. Studies in animals have however, revealed peri- and post-natal toxicity of tiagabine at very high doses.

Clinical experience of the use of tiagabine in pregnant women is limited.

Consequently, as a precautionary measure, it is preferable not to use tiagabine during pregnancy unless in the opinion of the physician, the potential benefits of treatment outweigh the potential risks.

No information on tiagabine during breast-feeding is available.

Consequently, as a precautionary measure, it is preferable not to use tiagabine during breast-feeding unless in the opinion of the physician, the potential benefits of treatment outweigh the potential risks.

Tiagabine may cause dizziness or other CNS related symptoms, especially during initial treatment. Therefore caution should be shown by patients driving vehicles or operating machinery.

Adverse events are mainly CNS related.

A full list of adverse reactions reported with tiagabine during clinical studies and post marketing experience is shown in the table below. Adverse reactions are listed below as MedDRA preferred term by system organ class and frequency (frequencies are defined as: very common ≥1/10, common ≥1/100 to <1/10, uncommon ≥1/1,000 to <1/100, rare (≥1/10,000 to <1/1,000); very rare (<1/10,000), not known (cannot be estimated from the available data):

The following undesirable effects have been reported with tiagabine:

In patients with a history of serious behavioural problems there is a risk of recurrence of these symptoms during treatment with tiagabine, as occurs with certain other anti-epileptic drugs.

Although not statistically significant, routine laboratory screening during placebo controlled studies showed a low white blood cell count (<2.5 × 10⁹ per litre) more frequently during tiagabine treatment (4.1%) than placebo (1.5%).

Postmarketing reports have shown that tiagabine use has been associated with new onset seizures and status epilepticus in patients without epilepsy treated by tiagabine for unapproved indication.

During post-marketing experience, there have been reports of vision blurred, vomiting, ataxia, abnormal gait, speech disorder, hostility, insomnia, dermatitis bullous, vesiculobullous rash, muscle twitching and amnesia. In case reports, amnesia occurred within days after initiation or dose increase of tiagabine and was reversible upon discontinuation of tiagabine or dose decrease.