Rectal drug delivery

Rectal rocket

• unique dosage form for persistent hemorrhoids

• designed to get the drug to the site of action

• holds the drug at the site of action for an extended period (slit for flatulence)

• available only as a compounded product

Advantages of rectal rockets

• it does not get lost in the butt but remains at the point of application

• treats both internal and external hemorrhoids at the same time

• the patient can expel gas without losing the suppository

Superior rectal vein vs middle and inferior rectal veins

The superior rectal vein (superior hemorrhoidal vein) drains into the portal vein where it undergoes first pass metabolism. The middle and inferior veins (hemorrhoidal veins) drain into the inferior vena cava, avoiding first pass metabolism

Advantages of rectal drug delivery

• minimize first pass metabolism

• avoid problems of oral administration

• suitable for patients unable to swallow

• provide local action

Disadvantages of rectal drug delivery

• poor patient acceptance

• erratic drug absorption from the rectal route

  • poor compliance + insertion technique

  • variable blood flow

  • rectal content

  • rectal mucosa and disease conditions

• not suitable for large volumes and for drugs that irritate the rectum

Fatty suppository bases

Cocoa butter, synthetic triglycerides

Water soluble/water miscible suppository bases

Glycerinated gelatin

PEG

fatty acid esters of PEGs

Fatty base with oil soluble active agent causes (fast/slow) release

slow

Fatty base with water soluble active agent causes (fast/slow) release

fast

Water base with oil soluble active agent causes what rate of release

medium

Warwe base with water soluble active agent causes what rate of release

medium

Desirable properties of suppository bases

either melts or disperses in the rectal fluid

solid at room temperature

non-irritating to rectal mucosa

• water soluble bases are irritating

How long should you wait after inserting a suppository to empty your bowels?

at least an hour

Rectal enema

• solution or suspension

• for cleansing/evacuation or provide local drug effect

Advantages of rectal foam

• spreads well in the rectal space, provides uniform coverage, and is retained in the rectal space better

• doesn’t flow so it doesn’t leak out

• used for the treatment of ulcerative colitis of the rectum (ulcerative proctitis)

Foaming agents/surfactants/emulsifiers in rectal foam

polyoxyl stearyl ether, emulsifying wax, fatty alcohols (cetyl alcohol)

solvents in rectal foam

propylene glycol, water

propellant in rectal foam

n-butane, isobutene, propane

geling agent in rectal gel

Hydroxypropyl methylcellulose

preservative in rectal gel

sodium benzoate

What makes mesalamine more favorable than sulfasalazine for managing IBD?

mesalamine is the active drug component of sulfasalazine (prodrug). Mesalamine has fewer side effects.

Are mesalamine products designed for local or systemic action?

local