Purpose: To investigate the adsorptive interaction of
Garcinia kola
with spiramycin, since the kola is
widely chewed as a tonic and spiramycin attains high concentrations in saliva.
Methods: Spiramycin solutions of different concentration were added to a fixed mass of
Garcinia kola
(200 mg), activated charcoal or Veegum®. Shaking was carried out at room temperature after which the
dispersion was filtered and the filtrate assayed for residual drug concentration. The process was
repeated under different equilibrium conditions of pH and ionic strength. The adsorption data obtained
for the three adsorbents were analyzed using Langmuir and Freundlich’s plots.
Results: At neutral pH, drug adsorprtion by
Garcinia kola, activated charcoal and Veegum® were 67,
54 and 71 %, respectively; differences in adsorption was not significant (p = 0.09). However, the other
two adsorbents exhibited adverse adsorption characteristics in terms of negative adsorption capacity (-
5.78 mol.kg
-1) and constant (-1141 mol
-1L). For each of the adsorbents, pH and ionic strength affected
the extent of adsorption, due to their effect on adsorbent surface charge. Correlation with Langmuir and
Freundlich relationships were poor, the correlation coefficient for the latter being 0.97, 0.894 and 0.351
for
Garcinia kola, Veegum® and activated charcoal, respectively.
Conclusion: The study reveals that
Garcinia kola significantly adsorbs spiramycin under alkaline
conditions comparable to salivary pH, and therefore should not be taken concurrently with the drug in
order to minimize reduction in drug levels.
