3.7 Flashcards
The rectum is the last ____ cm of the large intestine.
15 to 20
The anal canal is the last ____cm of the rectum.
4 to 5
The surface area of the rectum has no villi, thus has a relatively (high or low) absorptive surface area.
low
The rectal mucosa is the mucous layer of the rectum (rectal fluid) with a volume of ___ ml (100 micrometers thick) and pH of 7.5
3
Rectal fluid is about 3 mL which is very little fluid for drug …
dissolution
The epithelium of the rectal mucosa is cylindrical single cell layer and goblet cells, but it transitions to a _____ epithelium as it reaches the anus.
squamous
______ rectal veins drain to the general circulation (without hepatic first pass metabolism)
lower and middle
____ rectal vein drains to the hepatic portal vein which is more GI-like (with hepatic first pass metabolism)
superior
Venous Anastomoses is the opening; a natural communication between …
two blood vessels
____ can help spread the dosage form and are stimulated by colonic contents– Rectal Motility
Rectal contractions
Advantage of Rectal Drug delivery if the oral route is les desirable for the drug…
Bypass drug inactivation of upper GIT
(chemical or enzymatic)
Partial avoidance of Hepatic first pass metabolism (only absorbed in the lower rectum to bypass portal drainage)
The rate of absorption is not affected by gastric emptying or GI transit time
Disadvantage of Rectal Drug delivery …
Poor, slow, erratic drug bioavailability
- Low surface area
- Low fluid content
- complex blood drainage
(lower suppository placement– avoid portal drainage- which is needed if systemic effect is desirable)
Rectal fluid pH has little buffer capacity meaning the ____ will likely determine the rectal fluid pH
dosage form
rectal veins are heavily ____
anastomosed
If bioavailability is crucial it is preferred to go to the (oral or rectal route)
oral (not rectal since there is poor drug bioavailability)
