# How to Make Hard-to-Absorb Medicines Easier for the Body to Use

> A method for mixing specific chemical compounds with surfactants to help the body absorb them more effectively.

- **Patent:** US 5002952
- **Original title:** Readily absorbed pharmaceutical composition
- **Owner:** Green Cross Corp Japan
- **Granted:** 1991
- **Status:** Public domain (expired)
- **Times cited:** 16
- **Field:** pharmaceutical, biotech

## What it does

This patent describes a way to improve how the body absorbs a class of chemicals called benzoyl urea compounds. These compounds are often difficult for the body to process because they do not dissolve well in water. By mixing these compounds with specific nonionic surfactants—substances that help bridge the gap between water and oil—and grinding them into tiny particles (0.2 to 10 micrometers), the inventors created a formula that is much easier for the body to take up. The process involves wet-milling the mixture, often using glass beads, to ensure the particles are small enough to be effective.

## What it does NOT cover

- Does not cover benzoyl urea compounds outside the specific chemical structure defined in claim 1.
- Does not cover the use of ionic surfactants, which have a different chemical charge profile.
- Does not cover methods of administration that do not rely on this specific particle-size reduction process.
- Does not cover the synthesis of the benzoyl urea compound itself, only the composition and its preparation.

## The clever bit

The innovation lies in the combination of mechanical wet-milling with specific nonionic surfactants to stabilize the resulting micro-particles, preventing them from clumping back together and ensuring consistent absorption.

## Real-world examples

1. Formulations for agricultural pesticides
2. Experimental drug delivery systems for poorly soluble compounds

## Why it matters

Many potent drugs fail in clinical trials simply because the body cannot absorb them efficiently. This patent addresses the 'bioavailability' problem, which is a major hurdle in pharmaceutical development. By providing a standardized way to formulate these compounds, it allows researchers to turn promising chemical candidates into viable, usable medicines.

## Frequently asked questions

### What does How to Make Hard-to-Absorb Medicines Easier for the Body to Use cover?

A method for mixing specific chemical compounds with surfactants to help the body absorb them more effectively.

### Who owns patent US 5002952?

Green Cross Corp Japan owns this patent, granted in 1991.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 5002952 cited by?

This patent has been cited by 16 later patents that build on its ideas.

### What problem does this patent solve?

Many potent drugs fail in clinical trials simply because the body cannot absorb them efficiently. This patent addresses the 'bioavailability' problem, which is a major hurdle in pharmaceutical development. By providing a standardized way to formulate these compounds, it allows researchers to turn promising chemical candidates into viable, usable medicines.

### What does this patent NOT cover?

Does not cover benzoyl urea compounds outside the specific chemical structure defined in claim 1.

**Full plain-English explainer:** https://patentbrief.org/patent/us/5002952/duragesic-fentanyl-patch

**Original patent:** https://patents.google.com/patent/US5002952

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._