Dependence of copolymer composition, swelling history, and drug concentration on the loading of diltiazem hydrochloride (DIL.HCl) into poly[( N-isopropylacrylamide)- co-(methacrylic acid)] hydrogels and its release behaviour from hydrogel slabs

The loading of an antihypertensive cationic drug, diltiazem hydrochloride (DIL.HCl), into poly( N-isopropylacrylamide) [P( N-iPAAm)], poly(methacrylic acid) [P(MAA)], and their poly[( N-isopropylacrylamide)- co-(methacrylic acid)] P[( N-iPAAm)- co-(MAA)] hydrogels as well as their release behaviour...

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Bibliographic Details
Published in:Journal of controlled release 2005-02, Vol.102 (3), p.595-606
Main Authors: Sousa, Ricardo G., Prior-Cabanillas, Alberto, Quijada-Garrido, Isabel, Barrales-Rienda, José M.
Format: Article
Language:English
Subjects:
Acrylamides - chemistry
Acrylamides - pharmacokinetics
Biological and medical sciences
Diltiazem - chemistry
Diltiazem - pharmacokinetics
Diltiazem hydrochloride
Drug loading
Drug release
General pharmacology
Hydrogels - chemistry
Hydrogels - pharmacokinetics
Medical sciences
Pharmaceutical technology. Pharmaceutical industry
Pharmacology. Drug treatments
Poly[( N-isopropylacrylamide)- co-(methacrylic acid)] copolymers
Polymethacrylic Acids - chemistry
Polymethacrylic Acids - pharmacokinetics
Stimuli-sensitive polymers
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Summary:The loading of an antihypertensive cationic drug, diltiazem hydrochloride (DIL.HCl), into poly( N-isopropylacrylamide) [P( N-iPAAm)], poly(methacrylic acid) [P(MAA)], and their poly[( N-isopropylacrylamide)- co-(methacrylic acid)] P[( N-iPAAm)- co-(MAA)] hydrogels as well as their release behaviour have been investigated. For this purpose, two series of hydrogels have been tested, one previously soaked under acidic pH (treated hydrogels) and the other from the synthesis and washed in deionized water (untreated hydrogels). For the drug loading, these two series of hydrogels have been soaked in drug solutions with different concentrations. DIL.HCl amounts loaded by the gels as well as swelling degrees as a function of both hydrogel composition and DL.HCl concentration in the loading solution have been analyzed. Due to the interactions among DIL.HCl and the MAA group, “untreated” enriched MAA copolymer hydrogels present the highest drug load and loading efficiency. A DIL.HCl concentration of 320 μm/mL has been employed to load copolymers for release experiments, because for this concentration, hydrogels reach relative high drug load with a still high efficiency of loading. Release has been tested in three media, namely, fresh water (Milli-Q grade, pH 7.0), 0.1 N hydrogen chloride (pH 1.2), and a phosphate buffer (pH 7.0). In general, release is lower in fresh water and acidic media than in phosphate buffer. To explain these results, the effect of temperature, medium, and composition on the pH and thermo sensitivity of the hydrogels as well as the diltiazem–polymer interactions have been taken into account.
ISSN:0168-3659
1873-4995
DOI:10.1016/j.jconrel.2004.10.025