The standard adult dose of Kaletra is 400mg lopinavir and 100mg ritonavir twice a day with food. Kaletra was originally available in capsules containing 133mg lopinavir and 33.3mg ritonavir, with a standard dose being three capsules twice a day. However, Abbott Laboratories has developed a new tablet formulation of Kaletra that was approved in the United States in October 2005 and in the European Union in July 2006. In contrast to the capsules, Kaletra tablets do not require refrigeration, making them an attractive option for the developing world^[1]. Each tablet contains 200mg lopinavir and 50mg ritonavir, reducing the daily pill burden from six capsules to four tablets. In developing and middle-income countries, the tablets will be marketed under the trade name Aluvia.

The new formulation has been shown to produce equivalent exposure and maximal blood concentrations of both drugs to the capsules. However, the new version has a lower risk of causing extreme peaks and troughs in blood drug levels and can be taken without regard to food intake^[2]. It is hoped that removal of some of the constituents of the current capsules may reduce the incidence of gastrointestinal side-effects in patients taking Kaletra. The capsule formulation is currently being phased out by Kaletra’s manufacturer, Abbott, in order to avoid confusion between the capsule and tablet versions of the drug.

A disadvantage of the new formulation is that it may be more difficult for patients on non-standard dosing schedules to achieve the correct levels of lopinavir and ritonavir in the blood. Abbott has stated that it plans to produce a half-dose paediatric version of the Kaletra tablet, but that this may not be available until the end of 2007. In the meantime, patients taking non-standard doses may need to continue to use the capsules, possibly on a named-patient basis, until the low-dose tablets are made available.

Once-daily dosing of Kaletra was approved in the United States for treatment-naive adults in May 2005 at a dose of 800mg lopinavir boosted by 200mg ritonavir, following favourable findings in a clinical trial^[3]. It is not recommended for treatment-experienced patients. A similar approval is unlikely to occur in Europe until more data have been collected on the efficacy of this dosing schedule. A particular concern is the risk of levels of lopinavir falling to low levels between once-daily doses: in a recent study, this occurred in six of 20 patients and could only be resolved by dose escalation in one patient^[4].

An oral solution of lopinavir is also available. One millilitre contains 80mg lopinavir and 20mg ritonavir. Standard adult dosing with the solution is 5ml twice daily.

Caution should be exercised in patients with HIV and hepatitis C co-infection, as mild to moderate hepatic impairment can increase blood levels of lopinavir by 30%.