Pregabalin as an anti-epileptic

Pregabalin is classified as an anti-epileptic drug (AED) which exerts an effect by binding to voltage-gated calcium channels in the Central Nervous System. One of the indications that generic pregabalin is therefore licensed for is adjunctive therapy in epilepsy.

The use of pregabalin as an AED raises a question over any potential risks to the patient of switching between different manufacturer’s products.

Can patients using pregabalin for epilepsy be safely switched to an alternative brand?

Historically, the advice with regards switching between different brands of AED has been to avoid it if at all possible. Different brands may have slight differences in pharmacokinetic profile with knock-on effects on bioavailability.

By switching brand there is a chance that a patient’s blood levels drop, lowering the anti-convulsive effect and risking a seizure. Apart from the potentially life-threatening nature of a seizure, it can also have knock-on effects on the patient’s quality of life, including the ability to drive a car. Conversely, an increase in plasma concentration could lead to adverse effects, impacting on adherence.

In order to provide a more evidence-based approach, in 2013 the Commission on Human Medicines investigated the risks associated with switching of AEDs. They looked at bioavailability as well as drug characteristics such as solubility, permeability and drug interaction profile. Their review allowed them to categorise each AED in terms of the risks associated with switching product.

Pregabalin has been classified as Category 3, the lowest level of risk. The advice for Category 3 drugs is:

“For these drugs it is usually unnecessary to ensure that patients are maintained on a specific manufacturer’s product unless there are specific concerns such as patient anxiety, risk of confusion or dosing errors”

The CHM did not identify any pharmacokinetic concerns over switching between different formulations of pregabalin.

So, the only real consideration for pharmacists is whether switching formulation would impair the patient’s adherence to treatment or their trust in their medication.

It is important that patients are involved in decisions about their treatment and so they should be consulted before any switch occurs.

Discussing the switch to an alternative formulation, seeking their consent and reassuring them on the efficacy of their new treatment should allay any concerns and maintain adherence. Where a joint decision to switch is made this should be recorded and the patient’s GP consulted.

In the interests of supporting patient adherence, it would still seem preferable to stick to one manufacturer’s product and to avoid regularly switching between formulations on an ad-hoc basis. The choice of product, however, is not dictated by previous history.

For a full discussion of the CHM review and the continuity of supply of AEDs we refer you to our Pharmacy Excellence module which is supported by a CPD recording template.