Different tablet formulations of 100 tablets each were prepared using direct compression. All powders were passed though
an 80-mesh sieve. The required quantity of drug, matrix polymer (natural and synthetic), and low-density powder were mixed
thoroughly. Talc and magnesium stearate were added as a glidant and a lubricant, respectively. Blending was carried out using
a laboratory-scale V-blender with a 100-g capacity (modelAP-01, Orchid Scientifics, Nashik, Maharashtra, India) for 30 min.
The blend was compressed with a multipunch tablet compressor (lab press, Cadmach Csi 670, India) at dwell times of 20 s and
under a pressure of 25 kg/cm2 . Each tablet contained 40 mg of famotidine and other pharmaceutical ingredients (see Table I). The tablets were round and
flat with an average diameter of 8.0 ± 0.1 mm, a hardness of 4–6 kg/cm2 , and a thickness of 4.0 ± 0.2 mm. The tablets were evaluated for weight variation, drug content, and floating lag time (see
Table II: Evaluation parameter of tablets of all batches.
In vitro buoyancy was determined by determining the floating lag time (i.e., the time period between placing the tablet in the medium
and the tablet floating) (15). The tablets were placed in a 100-mL beaker containing 0.1 N HCl. The time required for the
tablets to rise to the surface and float was defined as the floating lag time.
dissolution studies. The release rate of famotidine from the floating tablets (n = 3) was determined using United State Pharmacopoeia (USP) XXIV dissolution testing apparatus II (paddle method). The dissolution test was performed using 900 mL of 0.1 N HCl at 37
± 0.5°C and 50 rpm. A 10-mL sample of the solution was withdrawn from the dissolution apparatus hourly for 8 h, and the samples
were replaced with fresh dissolution medium. The samples were filtered through a 45-µm membrane filter and diluted to a suitable
concentration with 0.1N HCl. Absorbance of these solutions was measured at 265 nm using a Shimadzu (Kyoto, Japan) UV-1601
UV–vis double-beam spectrophotometer. Cumulative percentage of drug release was calculated using an equation obtained from
a standard curve.
Comparison of dissolution profiles.
The similarity factor (f
) given by scale-up and postapproval changes (SUPAC) guidelines for modified-release dosage forms was used as a basis to compare
dissolution profiles. The dissolution profiles are considered similar when f
is between 50 and 100 (16).