betadex and limaprost

Limaprost/α-cyclodextrin (CD)/β-CD ternary inclusion complex was prepared by freeze-drying a solution containing all three components. Under humid conditions, limaprost was more stable in the ternary α-/β-CD inclusion complex than in the binary α- or β-CD complex. Specifically, during storage at 30°C/75% relative humidity (R.H.) for 4 weeks, about 19% of limaprost degraded into 17S,20-dimethyl-trans-Δ(2)-prostaglandin A1 (referred as 11-deoxy-Δ(10)) in the β-CD complex, 8.1% degraded in the α-CD complex, and only 2.2% degraded in the α-/β-CD complex. The mechanism of limaprost stabilization in the presence of both CDs was investigated by Raman and solid-state NMR spectroscopy and powder X-ray diffractometry. The fast degradation of limaprost to 11-deoxy-Δ(10) in the β-CD complex was due to the rapid crystallization of β-CD from the complex, liberating the free amorphous drug, which is susceptible to degradation. The dissociation and crystallization of β-CD from the inclusion complex were suppressed by freeze-drying limaprost in the presence of both α- and β-CDs. In addition, the interaction between limaprost and the two CDs was reinforced by inclusion of different moieties of limaprost: α-CD predominantly included the alkyl ω-chain, whereas β-CD included the five-membered ring. Thus, a stable ternary inclusion complex was formed that included limaprost, maintaining the amorphous state of the complex and dramatically stabilizing the drug under humid conditions.

Topics: alpha-Cyclodextrins; Alprostadil; beta-Cyclodextrins; Chemistry, Pharmaceutical; Crystallization; Excipients; Freeze Drying; Magnetic Resonance Spectroscopy; Pharmaceutical Solutions; Solubility

The inclusion mode of Limaprost in the presence of α- and β-cyclodextrins (CDs) was investigated to gain insight into the stabilization mechanism of Limaprost-alfadex upon the addition of β-CD in the solid state. The inclusion sites of α- and β-CDs were studied by NMR spectroscopic and kinetic methods. With the addition of α- and β-CDs, displacements in (13)C chemical shifts of prostaglandin F2α (PGF2α) were observed in the ω-chain and the five-membered ring, respectively, of the drug. Similar shift changes were observed with the addition of both α- and β-CDs. In two-dimensional (2D) (1)H-NMR spectra, intermolecular correlation peaks were observed between protons of PGF2α and protons of both α- and β-CDs, suggesting that PGF2α interacts with α- and β-CDs to form a ternary complex by including the ω-chain with the former CD and the five-membered ring with the latter. In kinetic studies in aqueous solution, Limaprost was degraded to 17S,20-dimethyl-trans-Δ(2)-PGA1 (11-deoxy-Δ(10)) and 17S,20-dimethyl-trans-Δ(2)-8-iso-PGE1 (8-iso). The addition of α-CD promoted the dehydration to 11-deoxy-Δ(10), while β-CD promoted the isomerization to 8-iso, under these conditions. In the presence of both α- and β-CDs, dehydration and isomerization were also accelerated, supporting the formation of the ternary Limaprost/α-CD/β-CD complex.

Topics: alpha-Cyclodextrins; Alprostadil; beta-Cyclodextrins; Magnetic Resonance Spectroscopy; Molecular Structure; Water

Stabilization against humidity of Limaprost (a prostaglandin E₁ derivative), which is currently marketed as Opalmon, was undertaken using β-cyclodextrin (β-CD). Aqueous solutions of Limaprost alfadex/dextran 40 were lyophilized with and without β-CD. Limaprost alfadex lyophilized with β-CD was more chemically stable in humid conditions than that without β-CD. Moreover, the addition of β-CD as an excipient to tablets of these lyophilized composites remarkably improved the stability of Limaprost, and Limaprost in this moisture-resistant formulation was chemically stable for 19 weeks at 30°C, 75% relative humidity (R.H.). Chemical analysis of Limaprost and its degradation products indicated that degradation proceeded in the inclusion form (i.e., within the CD cavity). Solid (2)H-NMR spectroscopic studies showed that β-CD constrained the molecular mobility of water in the solid state. These results suggested that the stabilization of Limaprost by β-CD was at least partly due to the restricted molecular mobility of water, which acted as a catalytic species for the degradation, and also to the protection of the five-membered ring of Limaprost from water catalytic dehydration through inclusion complex formation with β-CD.

Topics: alpha-Cyclodextrins; Alprostadil; beta-Cyclodextrins; Dextrans; Drug Stability; Excipients; Freeze Drying; Humidity; Tablets