Quetiapine extended-release* tablets (Seroquel XR) were added to the Schedule of Pharmaceutical Benefits on 1 November 2008 as a streamlined authority-required listing for schizophrenia.

The extended-release tablets come in different strengths to those of the existing immediate-release tablets, and dosing and administration has changed slightly. Prescribers will need to instruct patients carefully to prevent confusion between the two formulations. There is no compelling reason to switch people who are currently stable on quetiapine immediate-release tablets to extended-release tablets.

Quetiapine extended-release tablets are not currently indicated or PBS listed for mania. The existing streamlined authority listings of immediate-release quetiapine for schizophrenia and acute mania remain unchanged. See theNPS RADAR brief item Quetiapine (Seroquel) PBS listed for acute mania for details of this listing.

* This formulation is referred to as 'modified release' in the TGA-approved product information and the Schedule of Pharmaceutical Benefits.

There is no evidence that extended-release tablets improve efficacy, tolerability or adherence

Once-daily dosing with quetiapine extended-release tablets is equivalent to twice-daily dosing with quetiapine immediate-release tablets, e.g. quetiapine extended release 600 mg once daily is equivalent to quetiapine immediate release 300 mg twice daily. Comparative trials have found no difference in efficacy or tolerability between the 2 formulations, and have not assessed the relationship between dosing frequency and adherence.1,2

Some people may prefer once-daily dosing with the extended-release tablets, but immediate-release tablets give greater flexibility in dosing and in timing with respect to meals.

When switching is appropriate, patients can switch directly from twice-daily immediate-release tablets to an equivalent total daily dose of the extended-release tablets, taken once daily.3 Some people may need dose adjustment.3

The Pharmaceutical Benefits Advisory Committee (PBAC) found that the extended-release tablets were as effective as quetiapine immediate-release tablets (Seroquel) for no greater cost.4

Quetiapine extended-release tablets are taken once daily

People may prefer evening dosing to minimise any daytime sleepiness. Extended-release tablets should not be chewed, crushed or split.3

Extended-release quetiapine should not be taken with food. In one study using this formulation, a high-fat meal increased the peak blood levels of quetiapine and overall absorption.3 Raised blood levels of quetiapine may increase the risk of adverse effects.

Provide clear information to patients to help avoid confusion

Most of the extended-release tablets have different shapes and markings to the immediate-release tablets (see Table 1). Note however that the quetiapine extended-release 400 mg tablet has a similar appearance to the quetiapine immediate-release 300 mg tablet.

Table 1 Appearance of immediate-release and extended-release quetiapine tablets
Immediate release
Extended release
25 mg

50 mg

100 mg
200 mg

300 mg
300 mg

400 mg

If switching from another antipsychotic or from quetiapine immediate-release tablets, provide written instructions about how many tablets to take each day and at what time, and remind the patient to dispose of any old medicines that are no longer needed.

Discuss the Seroquel XR consumer medicine information (CMI) leaflet with the patient.

The approved dose range differs from that of the immediate release tablets

Adjust the dose within the usual effective range of 400–800 mg daily, depending on the clinical response and adverse effects.3 Elderly or frail patients, people with hepatic impairment, or people with a predisposition to hypotensive reactions may require a lower target dose.3,5 Daily doses higher than 600 mg have not shown greater efficacy in trials, although some individuals may benefit from a higher dose.6 Note that the dose range of 400–800 mg daily for quetiapine extended release differs from the approved dose range for quetiapine immediate release of 150–750 mg daily for schizophrenia.7