Oblikovanje i vrednovanje ciklodekstrinskih terapijskih sustava za oralnu primjenu zaleplona

doctoral thesis

• Title (english): Formulation and evaluation of cyclodextrin-based drug delivery system for oral application of zaleplon
• Author: Jasna Jablan
• Mentor: Mario Jug (mentor)
• Mentor: Nikola Kujundžić (komentor)
• Committee member: Renata Jurišić Grubešić (predsjednik povjerenstva)
• Committee member: Anita Hafner (član povjerenstva)
• Committee member: Biserka Cetina Čižmek (član povjerenstva)
• Granter: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of pharmaceutical technology); Zagreb
• Defense date and country: 2014-07-04, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Pharmacy; Pharmacy
• Universal decimal classification (UDC): 615 - Pharmacology. Therapeutics. Toxicology

Abstract

Nesanica je jedan od najčešćih poremećaja spavanja koji zahvaća oko 30% odrasle populacije, a značajno je
češći kod starije populacije i psihičkih bolesnika. Zahvaljujući svojim farmakološkim svojstvima, zaleplon je hipnotik
izbora za kratkotrajno liječenje nesanice. Međutim, slaba topljivost i razgradnja u jetri ograničavaju mu oralnu
bioraspoloživost na samo 30%. Stoga je cilj ovog rada pripremom inkluzijskih kompleksa s ciklodekstrinima
poboljšati topljivost lijeka u vodi, a uklapanjem u oblik s kontroliranim oslobađanjem razviti novi terapijski sustav
koji bi mogao značajno unaprijediti terapijsku učinkovitost ovog lijeka.
Spektrofluorimetrijska i solubilizacijska ispitivanja su pokazala da β-ciklodekstrin sa zaleplonom stvara
komplekse prikladne stabilnosti, no topljivost nastalog kompleksa je ograničena. Od kemijski modificiranih derivata,
nasumično metilirani β-ciklodekstrin se pokazao najprikladnijim, dok je topljivost i stabilnost inkluzijskih kompleksa
zaleplona sa sulfobutil-β-ciklodekstrinom i hidroksipropil-β-ciklodekstrinom nešto niža. Nastajanje inkuzijskih
kompleksa s navedenim derivatima ciklodekstrina je potvrđeno primjenom 1H NMR spektroskopije, a određena je i
njihova struktura. Sustav karakterizira istovremeno prisustvo dva načina vezanja. Prvi, dominantni način uključuje
inkluziju fenilnog prstena molekule zaleplona u centralnu šupljinu molekule ciklodekstrina, a drugi inkluziju
pirazolo[1,5-a] pirimidinskog prstena molekule lijeka, dok je nastajanje kompleksa višeg reda isključeno.
Termodinamička ispitivanja su pokazala da je nastajanje kompleksa zaleplona s β-ciklodekstrinom i njegovim
metiliranim i hidroksipropiliranim derivatima entalpijom uvjetovani proces, dok je kompleksiranje lijeka sa sulfobutil-
β-ciklodekstrinom entropijom vođen proces. U oba slučaja riječ je o spontanom procesu.
Dodatkom hipromeloze je značajno povećan solubilizacijski potencijal metiliranog β-ciklodekstrina uslijed
nastajanja ternarnih kompleksa lijek-ciklodekstrin-polimer, dok hidrofilni polimeri nisu utjecali na topljivost i
stabilnost kompleksa zaleplona s β-ciklodekstrinom. Binarni i ternarni kompleksi zaleplona s navedenim
ciklodekstrinima i hidrofilnim polimerima u čvrstom stanju pripremljeni su tehnikom sušenja raspršivanjem.
Diferencijalna pretražna kalorimetrija, difrakcija rentgenskih zraka na prašku te pretražna elektronska mikroskopija su
pokazale djelomičnu amorfizaciju lijeka u binarnim i ternarnim kompleksima s β-ciklodekstrinom, dok su kompleksi s
metiliranim-β-ciklodekstrinom bili u potpunosti amorfne strukture. Binarni kompleksi s metiliranim-β-
ciklodekstrinom te ternarni kompleksi s metiliranim-β-ciklodekstrinom i hipromelozom bili su najučinkovitiji u
povećanju topljivosti zaleplona u odnosu na ostale komplekse. Korištenjem manitola kao topljivog punila te ternarnog
kompleksa zaleplona s metiliranim β-ciklodekstrinom i hipromelozom pripremljene su tablete koje omogućuju
oslobađanje doze lijeka u samo 5 minuta, osiguravajući brz početak djelovanja lijeka. Topljivi kompleksi zaleplona s u
vodi topljivim, polimernim derivatom ciklodekstrina su pripremljeni i tehnikom mljevenja u vibracijskim
mikromlinovima. Nakon 90 minuta mljevenja pri frekvenciji od 24 Hz dobiven je amorfni produkt koji otapanjem u
vodi prelazi u inkluzijski kompleks, što je dokazano 1H-NMR spektroskopijom.
Primjenom tehnike sušenja raspršivanjem pripremljene su mikrosfere s pH ovisnim oslobađanjem zaleplona
kao novi terapijski sustav za liječenje nesanice koju karakterizira prerano buđenje te nemogućnost naknadnog
usnivanja. Matriks koji sadrži 80% Eudragita S100 i 20% glicerolmonostearata pokazao se optimalnim u sprječavanju
neželjenog oslobađanja lijeka pri nižim pH-vrijednostima medija, dok je uklapanjem 50% doze lijeka u obliku
inkluzijskog kompleksa s metiliranim β-ciklodekstrinom osigurano potpuno oslobađanje lijeka u umjetnom crijevnom
mediju, kinetikom nultog reda (k0=155 μg/min).

Abstract (english)

Insomnia is one of the most common sleep disorders affecting about 30% of adult population, while its
prevalence is even higher among elderly and psychiatric patients. Pharmacological properties makes zaleplon the drug
of choice for the short term treatment of insomnia, but its low aqueous solubility and intensive metabolism in liver are
reducing its oral bioavailability to only 30%. Therefore, the aim of this work was to improve aqueous solubility of
zaleplon through inclusion complexation and to develop a novel drug delivery system able to enhance its therapeutical
efficiency.
Spectrofluorimetric and phase solubility studies showed that parent β-cyclodextrin forms stable inclusion
complexes with zaleplon, but aqueous solubility of the complexes formed was limited. Among chemically modified β-
cyclodextrin derivatives, randomly methylated derivative was the most efficient, while the solubility and stability of
zaleplon complexes with sulphobutyl- and hydroxypropyl-β-cyclodextrin was less pronounced. The inclusion complex
formation in all cases was confirmed by 1H-NMR spectroscopy. The structure of the complexes formed was
characterised by the presence of two different binding modes which existed simultaneously in the solution. The first
and the dominant one occurs through inclusion of phenyl moiety of the drug into central cavity of cyclodextrin
molecule, while the other involves the inclusion of the pyrazolo[1,5-a]pyrimidine ring of the drug. The formation of
higher order complexes was not demonstrated. Thermodynamic studies showed that complexation of zaleplon with β-
cyclodextrin and its randomly methylated and hydroxypropylated derivatives was enthalpy driven, while entropy
driven complexation was observed in case of sulphobutyl-β-cyclodextrin. In all cases, inclusion complex formation
was a spontaneous process.
Addition of hypromellose enhanced significantly the solubilising and complexing potential of randomly
methylated β-cyclodextrin due to ternary complex formation, while hydrophilic polymers had no effect on solubility
and stability of zaleplon complexes with parent β-cyclodextrin. Binary and ternary zaleplon complexes with
cyclodextrins and polymers tested were prepared by spray-drying. Differential scanning calorimetry, X-ray powder
diffractometry and scanning electron microscopy showed only partial drug amorphization of the drug in binary and
ternary complexes with β-cyclodextrin, while all complexes with randomly methylated β-cyclodextrin were
completely amorphous. The inclusion complex formation in spray-dried products was confirmed by the solid state
NMR. Binary and ternary complexes with randomly methylated β-cyclodextrin and hypromellose were the most
efficient in increasing the dissolution rate of zaleplon. The use of mannitol as a soluble filler and ternary inclusion
complex with randomly methylated β-cyclodextrin and hypromellose allowed formulation of tablets which released
the complete drug dose in 5 minutes, providing fast onset of drug action. Highly soluble zaleplon complexes with
soluble, polymeric β-cyclodextrin derivative were also prepared by co-grinding in high energy vibrational micromill.
Co-grinding at frequency of 24 Hz resulted in an amorphous product which is readily soluble in water, forming
inclusion complexes as demonstrated by 1H-NMR spectroscopy.
Spray-drying technique was used to prepare pH-responsive zaleplon microspheres with delayed release
properties as a novel drug delivery system for treatment of specific type of insomnia characterised with premature
awaking and inability to fall asleep again. Matrix containing 80% of Eudragit S100 and 20% of glycerol monostearate
was demonstrated to be optimal, preventing the drug release at high pH-values. The incorporation of 50% of the drug
dose in form of binary inclusion complex with randomly methylated β-cyclodextrin ensured complete drug release in
simulated intestinal media, with the zero-order release rate (k0=155 μg/min).

• Keywords: zaleplon; ciklodekstrini; inkluzijski kompleksi; topljivost; sušenje raspršivanjem; Eudragit; mikrosfere; oslobađanje lijeka
• Keywords (english): zaleplon; cyclodextrins; inclusion complexes; solubility; spray-drying; Eudragit; microspheres; pHdependent drug release
• Language: croatian
• URN:NBN: urn:nbn:hr:163:755257
• Study programme: Title: Pharmacy and biochemistry; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor znanosti (doktor znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2016-11-15 16:11:53