Long-term injectable drug delivery systems (DDS)

Types of Long-Term Injectable DDS:

1. Microspheres and Nanoparticles:

Mechanism: Biodegradable polymers (e.g., PLGA) encapsulate the drug, gradually releasing it as the polymer degrades.

Applications: Hormones (like leuprolide), antipsychotics, and cancer therapies.



2. Implants:

Mechanism: Small rods or devices are surgically or subcutaneously implanted, slowly releasing drugs.

Applications: Contraceptives (e.g., Nexplanon), opioid addiction treatment (e.g., buprenorphine implants).



3. Liposomes and Lipid-based Systems:

Mechanism: Encapsulate drugs within lipid bilayers, releasing them slowly.

Applications: Cancer treatments (like liposomal doxorubicin) and vaccines.



4. Hydrogels:

Mechanism: Hydrophilic polymers that swell in bodily fluids, releasing drugs over time.

Applications: Insulin delivery, anti-inflammatory drugs.


Advantages:

Improved Patient Compliance: Reduces the frequency of injections.
Controlled Release: Maintains therapeutic drug levels, minimizing peaks and troughs.
Reduced Side Effects: Consistent drug levels help reduce adverse effects.
Targeted Delivery: Implants or depot systems can be localized for site-specific treatment.


Challenges:

Formulation Complexity: Requires careful design to ensure stability and consistent release.
Biodegradability: Some materials may leave residues or cause immune responses.
Surgical Insertion: Implants might require minor surgery.
Cost: Can be expensive due to advanced technology and materials.



Examples of Long-term Injectables:

Zoladex (Goserelin): Used for hormone-dependent cancers.
Risperdal Consta (Risperidone): Long-acting injectable antipsychotic.
Lupron Depot (Leuprolide): Treats prostate cancer and endometriosis.



Future Trends:

Smart DDS: Responsive systems that release drugs based on physiological triggers (e.g., pH, temperature).
Biodegradable Implants: Improved materials for zero-residue implants.
Gene Therapy Delivery: Long-term injectables for genetic treatments.