Pharmacology: Suppositories Overview

Suppositories: Dosage Form & Administration

• Suppositories are solid dosage forms designed to melt or dissolve at body temperature, releasing medication locally or systemically.

• Drawback: A significant issue with suppositories is variability in absorption rates due to factors like individual physiology, rectal contents, and drug properties.

• Benefit: Despite drawbacks, suppositories offer advantages for patients who cannot take oral medications or prefer a non-invasive route.

• Target Patient Group: Patients with nausea, vomiting, or impaired swallowing benefit significantly from suppositories.

• Rectal Advantage: Rectal administration bypasses the first-pass metabolism in the liver, often resulting in higher drug bioavailability.

• Inter-Subject Variation: Differences in rectal anatomy, intestinal motility, and individual drug-receptor interactions contribute to varying absorption rates among individuals.

• Related Dosage Forms: Besides suppositories, pessaries (vaginal suppositories) are another relevant dosage form.

Suppository Characteristics & Types

• Disadvantage: One potential disadvantage of suppositories is that they can cause rectal irritation or discomfort.

• Advantage: Rectal administration allows for faster absorption of drugs compared to oral administration.

• Shape: Rectal suppositories are typically molded into a torpedo shape for easier insertion.

• Weight: Adult rectal suppositories typically weigh around 2 grams.

• Pessary: Vaginal suppositories are also known as pessaries.

• Reason for Rectal Use: When oral administration is ineffective or contraindicated, rectal administration is often preferred.

• Urethral Suppository Diameter: The usual diameter range for urethral suppositories is 0.5 to 1 cm.

• Rectal Route Practicality: The rectal route can be less practical for drug administration due to potential discomfort, embarrassment, and the need for patient cooperation.

• Urethral Suppository Length: The length of urethral suppositories varies depending on the intended use, with a typical range of 2 to 5 cm.

• Rectal Suppository Length: The typical length range for rectal suppositories is 3 to 5 cm.

• Urethral Suppository Characteristic: Unlike most suppositories, urethral suppositories are cylindrical in shape.

Suppository Bases & Drug Release

• Water-Soluble Drug Release: Water-soluble drugs released from a fatty suppository base often have a slow and erratic release rate.

• Preferred Rectal Base: Cocoa butter, with its soothing action, is preferred for rectal administration.

• Cocoa Butter Disadvantage: One major disadvantage of using cocoa butter as a suppository base is its sensitivity to temperature fluctuations.

• Cocoa Butter Property: The polymorphism of cocoa butter is not favorable for suppository use, as it affects its melting point and solidification properties.

• Rectal Pressure: Suppository pressure in the rectum is exerted by the rectal sphincter muscle during insertion.

• Semi-Synthetic Fatty Bases: Semi-synthetic fatty bases typically do not contain hydrogenated vegetable oils.

• Absorption Enhancement: Sodium lauryl sulfate is a surfactant known for its ability to enhance absorption for peptide-like drugs.

Vaginal Route & Administration

• Vaginal pH: The typical pH of vaginal fluids during the menstrual cycle is around 4.5.

• Ketoconazole Problem: At acidic pH levels, ketoconazole becomes protonated, which reduces its absorption and effectiveness.

• Rectal Absorption Influence: The highly vascularized rectal mucosa is a major factor influencing drug absorption from rectal suppositories.

• Vaginal Systemic Effect: Drug absorption from the vaginal route can lead to potential systemic effects.

• Vaginal Vascularization: The rich network of blood vessels surrounding the vaginal mucosa ensures its vascularization.

• Water-Soluble Drug Absorption: Slightly water-soluble drugs tend to absorb faster in the rectum due to its higher water content.

• Vaginal Route Characteristic: Drug delivery via the vaginal route allows for local and systemic drug action.

• Vaginal Mucosa Changes: Age and hormonal activity significantly impact the integrity and absorption capacity of the vaginal mucosa.

• Vaginal Advantage: Vaginal administration allows for targeted drug delivery to the reproductive system, bypassing the liver and gastrointestinal tract.

• Vaginal Administration Disadvantage: One disadvantage of vaginal administration is potential discomfort, leakage, and difficulty with insertion.

• Vaginal Film Purpose: Vaginal films are primarily used for estrogen replacement therapy.

• Vaginal Ring Release: Vaginal rings are designed with a reservoir that allows for controlled medication release over an extended period.

• Vaginal Tablet Component: Vaginal tablets typically contain acid-forming ingredients, which create a favorable environment for drug dissolution and absorption.

• Vaginal Product Effectiveness: The dissolution rate and absorption of vaginal products are crucial for their effectiveness after administration.

• Patient Reluctance: Some patients might be hesitant to use vaginal delivery systems due to social stigma, discomfort, or personal preference.

• Vaginal Semisolid Contact Time: In vaginal semisolids, the viscosity and gel-forming properties can increase contact time with the epithelial surface, promoting drug absorption and effectiveness.

• Vaginal Suppository Disadvantage: Compared to vaginal tablets, vaginal suppositories may have a shorter duration of action due to their rapid melting and release.

• Plastic Applicator Dosage Form: Vaginal creams and gels are commonly delivered via a plastic applicator to ensure local action within the vagina.