Supplementary material tables

Table 1: Quality target product profile (QTPP) for stimuli-responsive GR systems of acyclovir

QTPP Elements / Target / Justification
Dosage type / In situ gelling gastro retentive systems / Selection of in situ gelling GR systems help in increasing the GI residence time of the drug formulation leading to complete absorption within the therapeutic window
Dosage form / Sol form / The sol form provides ease of oral administration in paediatric and geriatric patient with improved compliance
Dosage strength / 800 mg / Once in a day dose of acyclovir
Route of administration / Oral / Most sought after route for delivery of acyclovir for treatment of herpes infections
Stability / At least 24 months
at refrigerated conditions / To maintain therapeutic potential of the drug during storage period

GI: Gastrointestinal; GR: Gastroretentive

Table 2: Critical quality attributes (CQAs) for stimuli-responsive GR systems of acyclovir and their justifications

Quality attributes of drug product / Target / Is this
a CQA? / Justifications
Physical
attributes / Color / Acceptable to patients / No / Color, odor and appearance were not considered as critical, as these are not directly linked to the efficacy and safety of dosage form.
Odor / No unpleasant order
Appearance / Acceptable to patients
Drug content / 100% / No / Drug content is a vital parameter for any pharmaceutical dosage form for attaining maximal plasma concentration of the drug. As the developed in situ formulation was liquid containing single once-a-daily dose of the drug solubilized in liquid vehicle containing, this variable was regarded as moderately critical.
Viscosity / 100% / Yes / Viscosity is considered as a critical parameter for in situ gel formulation. Sol form is required for easy dosing and the gel formed in situ should preserve its integrity without dissolving or eroding for required period of time.
Onset of floatation / Yes / Onset of floatation in the in situ gelling GR formulations is highly important, as it portrays the buoyant nature of the formulation, thus considered as highly critical.
Gel strength / Yes / Optimum value of gel strength is required for attaining desired controlled release profile of drug delivery and mucoadhesion characteristics of the formulation in the gastric region; hence was selected as highly critical.
Amount of drug release in 16 h (Q16h) / ≥ 90% / Yes / These parameters are the indicator of sustained release profile of drug release from the prepared formulations, thus were taken up as highly critical.
Time required for 60% drug release (T60%) / ~ 6 h


Table 3: Drug release kinetic parameters of the stimuli-responsive GR formulations (F1-F9) prepared as per the experimental design

Code / Formulation
Composition (mg) / Q16h (%) / T60% (h) / Release
Exponent
(n)
Na alginate / Gellan
F1 / 100 / 50 / 97.44 / 0.5519 / 1.735
F2 / 100 / 75 / 95.97 / 0.5162 / 2.246
F3 / 100 / 100 / 93.18 / 0.4318 / 2.889
F4 / 200 / 50 / 84.83 / 0.3831 / 3.551
F5 / 200 / 75 / 82.02 / 0.3286 / 4.258
F6 / 200 / 100 / 79.31 / 0.2923 / 6.124
F7 / 300 / 50 / 73.85 / 0.2623 / 8.765
F8 / 300 / 75 / 72.39 / 0.2492 / 9.309
F9 / 300 / 100 / 69.59 / 0.2283 / 11.685

Supplementary material figures

Figure 1: Gel strength of the different formulations prepared as per the experimental design

Figure 2: Linear correlation plots and residual plots for the studied CQAs, viscosity, gel strength, onset of floating, t60% and Q16h


Supplementary material text

1. HPLC analysis of acyclovir

Analysis of acyclovir was carried out using a previously reported reverse phase high performance liquid chromatography (RP-HPLC) bioanalytical method in rat plasma with minor modifications (Emami, Bazargan & Ajami, 2010). The chromatographic system (Shimadzu LC-2010C HT ver 3.01, M/s Shimadzu Corp., Kyoto, Japan) employed was equipped with a system controller, a quaternary gradient pump, a UV detector, a solvent delivery module, an auto-sampler and an auto injector. Chromatographic separation was achieved on C18 column (Thermo Hypersil-keystone ODS C18 column; 250 mm × 4.6 mm, 5 μm) using a mixture of 0.2 M phosphate buffer (pH 4.0) and acetonitrile at 95:5%v/v as the mobile phase. The operating parameters were set at a flow rate of 1.0 mL.min–1, sample injection volume of 10 µL, column oven temperature at 25°C and detection wavelength at 254 nm. Analytical data, thus obtained were processed using Shimadzu LC solution ver. 1.23 software ver 2.0.

2. Plasma sample preparation

Rat plasma samples were prepared by addition of 400 µL phosphate buffer in 200 µL of plasma in glass tubes. All the samples were thoroughly mixed by agitation for 30 s followed by addition of 600 µL acetonitrile for precipitation of proteins. The tubes were centrifuged for 10 min at 10,000 rpm (5590 × g). The supernatant layer was filtered through 0.45 µm filter (Whatman membrane filters) and then freeze dried. The resultant was reconstituted with the mobile phase, i.e., phosphate buffer: ACN (95:5%v/v), which contained metronidazole 100 µg/mL as the internal standard. The samples were transferred to vials and 10 µL was injected in to HPLC system.