Formulation Study of Topically Applied Lotion: In Vitro and In Vivo Evaluation

Introduction: This article presents the development and evaluation of a new topical
formulation of diclofenac diethylamine (DDA) as a locally applied analgesic lotion.
Methods: To this end, the lotion formulations were formulated with equal volume of
varying concentrations (1%, 2%, 3%, 4%; v/v) of permeation enhancers, namely propylene
glycol (PG) and turpentine oil (TO). These lotions were subjected to physical studies (pH,
viscosity, spreadability, homogeneity, and accelerated stability), in vitro permeation, in
vivo animal studies and sensatory perception testing. In vitro permeation of DDA from
lotion formulations was evaluated across polydimethylsiloxane membrane and rabbit skin
using Franz cells. Results: It was found that PG and TO content influenced the permeation
of DDA across model membranes with the lotion containing 4% v/v PG and TO content
showed maximum permeation enhancement of DDA. The flux values for L4
were
1.20±0.02 μg.cm-2.min-1 and 0.67 ± 0.02 μg.cm-2.min-1 for polydimethylsiloxane and rabbit
skin, respectively. Flux values were significantly different (p < 0.05) from that of the
control. The flux enhancement ratio of DDA from L4
was 31.6-fold and 4.8-fold for
polydimethylsiloxane and rabbit skin, respectively. In the in vivo animal testing, lotion
with 4% v/v enhancer content showed maximum anti-inflammatory and analgesic effect
without inducing any irritation. Sensatory perception tests involving healthy volunteers
rated the formulations between 3 and 4 (values ranging between -4 to +4, indicating a
range of very bad to excellent, respectively). Conclusion: It was concluded that the DDA
lotion containing 4% v/v PG and TO exhibit the best performance overall and that this
specific formulation should be the basis for further clinical investigations.