L2 - Rectal

Define rectal drug delivery

Administration of pharmaceutical preparation via rectum for local or systemic effects

Name three types of dosage forms delivered via rectal route

Solid, liquid, and semi-soild dosage forms

Solid rectal dosage form

Suppository

Liquid rectal dosage form

Enema

Semi-solid rectal dosage form

Ointment and cream

Name some therapeutic applications of rectal administration

Rectal diseases such as perianal abscess, hemorrhoids, fissures, etc.

What are some therapeutic agents that can be delivered rectally?

Steroids, anti-inflammatory drugs, anti-cancer drugs, and NSAIDs

What is the only FDA approved rectal formulation for the ambulatory treatment of early status epilepsy?

Diazepam

The rectum is the last, usually empty, portion of the _______ intestine

large

1 multiple choice option

What is the pH of the rectum?

7.2-7.4 (neutral)

Why is the surface area of the rectum in the large intestine smaller than the small intestine?

Due to the lack of villi and microvilli

The rectum can be used to deliver drug via the _____ route

enteral

Describe the enteral route

The drug uses the digestive system to enter the body, including the mouth, stomach, small intestine, and anus

Do rectally administered drug act locally or systemically?

Both

2 multiple choice options

Systemic drug delivery via the rectal route can be useful for drugs which:

Possess limited absorption in upper GI tract, unstable to proteolytic enzymes, have strong first pass effect, cause irritation, and need high doses that cant be administered orally

What is the rectal route secondary to regarding preference?

Oral and IV

When does the rectal route become the first choice?

In conditions such as vomiting, objectionable taste, unconscious, difficulty swallowing, or inflammation at muscular site

What are the disadvantages of the rectal route?

Poor patient compliance, erratic absorption, limited surface area for absorption, and dissolution problems due to small fluid content in the large intestine

When do rectally administered drugs undergo the first pass effect?

When drugs from the rectum are absorbed into the superior hemorrhoidal vein that drains into the portal system, which then undergoes the first pass effect

Where should rectally administered drugs be placed to avoid absorption via the superior hemorrhoidal vein?

In the lower portion of the rectum

What is the drug absorbed by if administered to the lower part of the rectum?

It is absorbed and drained by the lower and middle hemorrhoidal veins which bypass the first pass effect

The epithelia of the rectum is made of:

A single layer of columnar or cuboidal cells and goblet cells. Good ability to absorb drugs

What is the surface area of the rectum?

200-400 cm^2 due to lack of villi/microvilli

The rectal region is extensively drained by the _______ circulation which increases systemic absorption of ______ drugs

lymphatic; lipophilic

Drugs that are absorbed from the rectum travel via _______ diffusion

passive

1 multiple choice option

What are the four categories of factors that affect rectal drug delivery?

Drug, formulation, pathology, and physiology associated factors

What drug associated factors affect rectal drug delivery?

Partition coefficient, solubility, degree of ionization, and particle size

What formulation associated factors affect rectal drug delivery?

Liquid, solid, and semi-solid

What pathology associated factors affect rectal drug delivery?

IBS, hemorrhoids, and GI infections

What physiology associated factors affect rectal drug delivery?

Rectal fluid, pH, rectal contents, rectal mucous, and motility