Comparative safety and efficacy of chitosan as nasal absorption enhancer of salmon calcitonin

Abstract

Five nasal enhancers, chitosan Japan (CS J), chitosan glutamate (CS G), dimethyl-P- cyclodextrin (DM- β -CD), hydroxypropyl-p-cyclodextrin (HP- β -CD) and lauroylcarnitine cldoride (LCC), were investigated for the efficacy, safety (membrane-damaging effect) and reversibility of their absorption enhancing activities. Using the in situ nasal perfusion, the efficacy of their absorption enhancing activities was evaluated by comparison of percentage dipeptide [D-Arg2]-Kyotorphin remaining in the perfusate. It was revealed that 0.1% LCC, 1.25% DM-P-CD, 0.5% CS J and 0.5% CS G were significantly more effective than 5.0% HP- β -CD and control saline, with 0.1% LCC gave the dipeptide absorption better than 0.5% CS G at pH 6.0. The magnitude of the nasal membrane-damaging effect was evaluated by measuring the extent of intracellular enzyme (lactate dehydrogenase (LDH)) release into the nasal perfusate during perfusion. The result was similar to that of the absorption enhancing activity. The relative membrane-damaging effect of these enhancers was found to be in the descending order of 0.1% LCC > 1.25% DM- β -CD, 0.5% CS G and 0.5% CS J > 5.0% HP- β -CD and control group. The significant correlation (p<0.05) was observed between the percent dipeptide remaining and the LDH content found in the nasal perfusate at T60. This indicates that the enhancers under study were able to enhance the nasal absorption of the model dipeptide by direct interaction with the nasal membrane. The enhancer's reversibility was evaluated by comparing the percent dipeptide and LDH content in the perfusate before and after removal of the enhancer. It was revealed that 0.1% LCC, 1.25% DM- β -CD, 0.5% CS J and 0.5% CS G exhibited good mucosal recovery in terms of both membrane integrity and permeability to dipeptide absorption. On the other hand, 5.0 % HP- β - CD and control saline exhibited very weak effects on the nasal mucosa and, therefore, did not show any reversibility. However, the ranking was not correlated between the efficacy of recovery based on the LDH release and the dipeptide absorption (p>0.05). For the in vivo study, 0.5% CS G was selected as a representative of chitosans to evaluate salmon calcitonin nasal absorption (sCT) in healthy male volunteers. It was found that after nasal administration with CS G, the plasma calcium decreased gradually, and reaching minimum of 89.5% of initial value at 6 hours post dose. The calcium level was significantly lower than the control saline and 1.33% DM- β -CD even at 9 hr after administration (p<0.05). The results indicate that chitosans especially CS G, appear to have a promising potential for use as a safe and effective nasal absorption enhancer in nasal peptide formulations provided that more clinical testing be conducted.