The oral delivery of drugs is the most preferred route of administration due to ease of administration. Drug bioavailability of pharmaceutical oral dosage forms is influenced by various factors. One important factor is the gastric residence time (GRT) of these dosage forms.
Indeed, gastric retention has received significant interest as most of the conventional oral delivery systems have shown some limitations related to fast gastric emptying time. A gastro retentive dosage form (GRDF) can overcome this problem.
Gastro retentive drug delivery (GRDDS) is one of the site specific drug delivery for the delivery of the drugs at stomach. It is obtained by retaining dosage form into stomach and drug is being released at controlled manner at specific site.
To design a successful GRDDS, it is necessary to take into consideration the physicochemical properties of the drug, physiological events in the GIT, formulation strategies, and correct combination of drug and excipients.
The drugs which are appropriate candidate for GRDDS includes-
• Drugs acting locally in the stomach. e.g. Antacids and drugs for H. Pylori viz., Misoprostol.
• Drugs that are primarily absorbed in the stomach. e.g. Amoxicillin
• Drugs that is poorly soluble at alkaline pH. e.g. Furosamide, Diazepam, Verapamil, etc.
• Drugs with a narrow absorption window. e.g. Cyclosporine, , Levodopa, Methotrexate etc.
• Drugs which are absorbed rapidly from the GI tract. e.g. Metronidazole, tetracycline.
• Drugs that degrade in the colon. e.g. Ranitidine, Metformin.
• Drugs that disturb normal colonic microbes e.g. antibiotics against Helicobacter pylori.
[wp_ad_camp_4]Gastro retentive drug delivery systems have emerged as a current approach of controlled delivery of drugs that exhibit an absorption window. Stomach specific drug delivery system that is GRDDS has some distinct advantages such as-
- Enhanced bioavailability
- Sustained drug delivery/reduced frequency of Dosing
- Targeted therapy for local ailments in the upper GIT
- Reduced fluctuations of drug concentration
- Improved selectivity in receptor activation
- Reduced counter-activity of the body
- Extended effective concentration.
- Minimized adverse activity at the colon.
On the contrary, Stomach specific drug delivery system has some limitations which includes-
- The drug substances that are unstable in the acidic environment of the stomach are not suitable candidates to be incorporated in the systems.
- These systems require a high level of fluid in the stomach for drug delivery to float and work efficiently.
- Not suitable for drugs that have solubility or stability problem in GIT.
- Drugs which are irritant to gastric mucosa are also not suitable.
- These systems do not offer significant advantages over the conventional dosage forms for drugs, which are absorbed throughout GIT.