A long-lasting oral preformulation of the angiotensin II AT1 receptor antagonist losartan.

Losartan (Los), a non-peptidic orally active agent, reduces arterial pressure through specific and selective blockade of angiotensin II receptor AT1. However, this widely used AT1 antagonist presents low bioavailability and needs once or twice a day dosage. In order to improve its bioavailability, we used the host: guest strategy based on ß-cyclodextrin (ßCD). The results suggest that Los included in ßCD showed a typical pulsatile release pattern after oral administration to rats, with increasing the levels of plasma of Los. In addition, the inclusion compound presented oral efficacy for 72 h, in contrast to Los alone, which shows antagonist effect for only 6 h. In transgenic (mREN2)L27 rats, the Los/ßCD complex reduced blood pressure for about 6 d, whereas Los alone reduced blood pressure for only 2 d. More importantly, using this host: guest strategy, sustained release of Los for over a week via the oral route can be achieved without the need for encapsulation in a polymeric carrier. The proposed preformulation increased the efficacy reducing the dose or spacing between each dose intake.

Supramolecular interactions between losartan and hydroxypropyl-ß-CD: ESI mass-spectrometry, NMR techniques, phase solubility, isothermal titration calorimetry and anti-hypertensive studies.

In this work, low soluble supramolecular complex between the losartan potassium (Los) and hydroxypropil-ß-cyclodextrin (HPßCD) were characterized throughout phase-solubility, NMR techniques ((1)H and 2D-ROESY) and isothermal titration calorimetry (ITC) in order to attain physical-chemical knowledge of the system. In addition, the hypertensive effect of composition Los/HPßCD was evaluated aiming to obtain a more efficient oral pharmaceutical composition. ESI mass spectrometry and ITC blank experiment demonstrate the presence of Los clusters at 30 mM pure solution. Phase-solubility experiments showed a "Bs" type system, due to the formation of a less soluble complex than pure Los. NMR demonstrated the short distance interactions between the Los and the cyclodextrin, where several possibilities of interactions were observed. ITC data suggest an average 1:1 stoichiometry of Los and the cyclodextrin. The complex demonstrated efficiency in hypertension control, presenting antagonist action on the pressure effect of angiotensin II within 30 h, as compared to Los alone, 6h, indicating that inclusion of Los in HPßCD enhanced the extent and duration of its antagonistic action. In this work, a model of interaction between Los and HPßCD was proposed based on dissociation of self-assembled Los followed by complexation with HPßCD.