Final answer:
Some drugs can get through the stomach environment if resistant to its acidic conditions, like alcohol and aspirin, while others like Valacyclovir use intestinal transporters to improve absorption. The majority of drugs are absorbed in the small intestine; transcellular and paracellular absorption are key mechanisms, and prodrugs can enhance bioavailability.
Step-by-step explanation:
What type of drug can get through the stomach environment? Primarily, drugs that are resistant to the acidic conditions and enzymatic activity in the stomach have a greater chance of passing through to the intestines where they can be absorbed into the bloodstream. Drugs such as alcohol and aspirin can be absorbed directly in the stomach to some extent. However, the majority of drug absorption occurs in the small intestine, and drugs that can passively diffuse through the cellular membranes are often successfully absorbed. One example is Valacyclovir, which uses intestinal transporters to increase permeability and has a significantly higher oral bioavailability than its parent drug, acyclovir. The drug properties, like avoiding efflux transporter P-glycoprotein and metabolism by gut wall enzymes, play a crucial role in enhancing oral absorption.
For drugs that are not effectively absorbed orally, alternative routes of administration, including intravenous or intramuscular injection, are preferred. Moreover, certain drugs designed as medical foods are specifically treated for enteric administration; they are intended to pass through the stomach undigested and break down in the intestines.
Some drugs can also take advantage of the properties of the GI tract such as the presence of transport proteins and can undergo transcellular or paracellular absorption. Ester prodrugs like L-Valyl ester prodrugs can also improve permeability and bioavailability of certain drugs by using transporter mechanisms.