Photostability of extended-release matrix formulations

Area of Science:

• Pharmaceutical Sciences
• Materials Science

Background:

• Drug photostability is well-researched, but UV-induced modifications in dosage form excipients, particularly functional polymers, are less understood.
• Polymers like hydroxypropylmethylcellulose (HPMC) and polyethylene oxide (PEO) are crucial for modulating drug release in extended-release formulations.
• The impact of UV radiation on these polymers and subsequent drug release characteristics requires thorough investigation.

Purpose of the Study:

• To investigate the effect of UV light exposure on the drug release profiles of extended-release matrix tablets formulated with HPMC or PEO.
• To evaluate the photostability of model drugs (nifedipine and diltiazem) within these formulations under UV irradiation.
• To assess the potential for UV-induced polymer modifications to alter drug release kinetics, focusing on the burst effect.

Main Methods:

• Formulation of extended-release matrix tablets using hydroxypropylmethylcellulose (HPMC) or polyethylene oxide (PEO) with nifedipine (photolabile) or diltiazem (photostable) as model drugs.
• Exposure of the prepared tablets to controlled UV light conditions.
• Dissolution testing of both UV-irradiated and non-irradiated tablets to compare drug release profiles.
• Evaluation of nifedipine photodecomposition and photoproduct formation during the dissolution process.

Main Results:

• Matrix tablets containing HPMC exhibited no significant alterations in drug release profiles after UV light exposure compared to non-irradiated controls.
• Matrix tablets containing PEO showed a marked increase in drug release rate, specifically a burst effect, within the initial minutes of dissolution testing following UV irradiation.
• Photodecomposition of nifedipine was observed, with photoproduct formation monitored during dissolution, indicating drug degradation under UV light.

Conclusions:

• UV light exposure can critically impact the drug release characteristics of extended-release tablets, particularly those formulated with polyethylene oxide (PEO).
• The observed burst effect in PEO-containing tablets due to UV irradiation poses a significant risk to therapeutic control.
• Hydroxypropylmethylcellulose (HPMC) appears to be a more robust excipient against UV-induced alterations in drug release profiles compared to PEO in these extended-release matrix systems.