Drug Delivery Systems
Buccal Drug Delivery Systems
Bioadhesive polymers-based DDSs:
Bioadhesive polymers can adhere onto the buccal mucosa prolonging the residence time of drug and thus, providing sustained release action.
Examples
Polycarbophil, Carboxymethyl cellulose sodium (CMC), Chitosan, sodium alginate.
Buccal Drug Delivery Systems
An ideal mucoadhesive polymer has the following characteristics :
1. It must be loaded substantially by the active compound.
2. It must swell in the aqueous biological environment of the site of absorption.
3. It must interact with mucus or its components for adequate adhesion.
4. It must allow controlled release of the active compound when swelled.
5. It must be excreted unaltered or biologically degraded to inactive, nontoxic oligomers.
Buccal Drug Delivery Systems
6. It must have sufficient quantities of hydrogen- bonding chemical groups.
7. It must possess high molecular weight.
8. It must possess high chain flexibility.
9. It must have the surface tension that may induce spreading into mucous layer.
Hydrogels-based DDSs:
Hydrogels are hydrophilic matrixes that are capable of swelling when placed in aqueous media. Normally, hydrogels are cross- linked so that they would not dissolve in the medium and would only absorb water. When drugs are loaded into these hydrogels, as water is absorbed into the matrix, chain relaxation occurs and drug molecules are released through the spaces or channels within the hydrogel network.
OraVescent ®DDSs:
ØThe OraVescent ® technology for oral transmucosal drug delivery is a special effervescent tablet that is placed in the oral cavity usually between the buccal and gingival tissues.
ØOraVescent technology was developed to enhance drug delivery, using fentanyl as the test compound
ØDDS is designed to dissolve over long period of times.
Mechanism of action
With respect to a weak base drug, we adjust the PH to a low value to improve dissolution, and later, to a higher pH to improve membrane permeation. This recommendation is based on the fact that the drug is predominantly in the ionized (salt) form at pH values less than the pKa and is predominantly in the un-ionized (base) form at pH values greater than the pKa.
OraVescent ®DDSs:
The formulation is composed of the drug together with citric acid, NaCO3 and NaHCO3
üCitric acid first dissolves pH
üSodium bicarbonate then dissolves pH
üThe reaction of an acid, such as citric acid, with a carbonate or bicarbonate (for example, sodium bicarbonate) produces CO2.
The effervescence-induced enhancement is mediated via the following effects:
üA solvent drag effect (concentration gradient) üOpening of tight junctions
üIncreasing the permeability through cell membrane
Recent advances in buccal drug delivery systems
The IntelliDrug device
The 'IntelliDrug' device represents a revolutionary method for delivering drugs for long-term chronic diseases through the buccal mucosa, according to the patient needs, in periods lasting days, weeks or months.
The system, which is the size of two molars, consists of a stainless steel intra-oral module containing an osmotic membrane, a drug reservoir that could additionally contain a chemical enhancer, a drug level sensor AND a flow sensor.
The drug is placed into the reservoir as a solid matrix.
Water from saliva enters the system through the osmotic membrane and solubilize the drug.
The pressurized drug solution is released by a microvalve.
A flow sensor combined with a concentration sensor allows metering of both the output flow rate of the drug solution on the buccal side and the depletion of the drug inside the reservoir.
The IntelliDrug device
