Introduction:
Intrauterine Drug Delivery Systems (IUDs) are devices placed directly into the uterus to deliver drugs locally.
These are commonly used for contraceptive purposes, wherein they release a controlled amount of either a copper ion or hormones to prevent pregnancy.
By delivering the drug directly to the target site, i.e., the uterus, it provides an effective means of achieving the desired pharmacological effect while minimizing systemic exposure.
Classification of IUDs
Intrauterine devices (IUDs) are primarily classified based on their composition and mechanism of action.
Here's a broad classification of IUDs:
1. Non-Hormonal IUDs:
Copper-bearing IUDs:
These are the most common type of non-hormonal IUDs. They release copper, which has spermicidal properties.
Examples: ParaGard (also known as Copper T 380A), Multiload Cu375, and others.
2. Hormonal IUDs:
Progestin-releasing IUDs:
These IUDs release a form of the hormone progestin, which thickens the cervical mucus to prevent sperm from reaching the egg and may also inhibit ovulation.
Examples: Mirena, Kyleena, Skyla, and Liletta.
3. Inert IUDs:
These are made from non-reactive materials that create a foreign body reaction in the uterus, producing an environment hostile to sperm and eggs.
They are less commonly used today due to lower efficacy compared to copper or hormonal IUDs.
Examples: Lippes Loop, Stainless Steel Rings.
4. Bioactive IUDs:
These IUDs have active substances other than hormones or copper, such as silver or gold, to enhance their efficacy or longevity.
5. Frame vs. Frameless:
A. Framed IUDs:
These have a plastic frame, usually in a T-shape, which holds the active component (like copper wire or hormonal reservoir).
Examples: ParaGard, Mirena.
B. Frameless IUDs:
These do not have a plastic frame. Instead, they attach directly to the uterine wall, potentially reducing the risk of expulsion and discomfort.
Example: GyneFix.
6. Size and Design Variations:
IUDs also differ in size and design, catering to a diverse range of uterine sizes and shapes.
This ensures women of all reproductive stages, from nulliparous to multiparous, can find an IUD that fits comfortably.
Each type of IUD has its indications, efficacy rates, and potential side effects.
The best choice for an individual largely depends on her health status, reproductive goals, and personal preferences. It's essential for women to consult with their healthcare providers to select the IUD that's right for them.
Mechanism of Action:
1. Non-medicated IUDs (like copper IUDs):
The presence of the IUD in the uterus causes a local inflammatory response.
The copper ions released also act as spermicides, impairing sperm function and preventing fertilization.
2. Hormonal IUDs:
They release progestin, which thickens the cervical mucus (preventing sperm from entering the uterus), inhibits ovulation, and thins the uterine lining, making it less receptive to a fertilized egg.
