(8) Novel Drug Delivery Systems II

 WHY NOVEL DRUG DELIVERY SYSTEMS?

• Enable controlled / extended release

• Reduce side effects & toxicity

• Improve patient compliance (less frequent dosing)

• Improve therapeutic outcomes

• Allow self-administration (outpatient use)

• Avoid costly interventions

IMPLANTS

Definition

• Device inserted into body for:

  • Therapeutic

  • Diagnostic

  • Prosthetic

 IMPLANTS

 FACTORS TO CONSIDER

• Erodibility

  • Biodegradable → no removal

  • Non-biodegradable → must remove surgically

• Irritation

  • Must be biocompatible

• Carcinogenicity

  • Some materials → cancer risk

• Dose dumping ✅⭐

  • Sudden release of large drug amount → toxicity

• Duration

  • Months → years depending on system

 TYPES OF IMPLANTS

Type	Degradable?	Removal	Duration
Reservoir	Non-degradable	Yes	~5 years
Matrix	Non-degradable	Yes	~2 years
Reservoir	Degradable	No	1–2 years
Matrix	Degradable	No	<1 year

examples of IMPLANTS - overview

Nexplanon

Norplant

Nexplanon

• Hormonal contraceptive

• 68 mg etonogestrel

• Works 3 years

• Contains barium sulfate → X-ray detectable

• Can remove anytime

Norplant

• 6 capsules

• Diffusion-controlled release

• 5 years

• 70 → 30 mcg/day release

• Discontinued in US

DRUG-ELUTING STENTS (DES)

Concept

• Stent placed in artery

• Releases drug slowly → prevents cell proliferation

DRUG-ELUTING STENTS (DES)

Mechanism

• Opens artery (mechanical)

• Releases drug (pharmacological)

DRUG-ELUTING STENTS (DES)

Examples - overview

Cypher Stent

Taxus Stent

Cypher Stent

• Drug: Sirolimus

• 80% released in 30 days

• Rest by 90 days

Taxus Stent

• Drug: Paclitaxel

• Polymer controls release

OCULAR DRUG DELIVERY

Problem

• Eye drops → 90% drug lost

• Only 5–10% bioavailable

OCULAR DRUG DELIVERY

Solution

• Implants → ↑ retention + ↑ bioavailability

 OCULAR DRUG DELIVERY

Types

1. Insert (easy)

2. Implants (require procedure)

 OCULAR DRUG DELIVERY

Insert (easy)

Lacrisert

• Hydroxypropyl cellulose

• Lubricates eye

• Dissolves → no removal

OCULAR DRUG DELIVERY

Drug	Type	Duration
Ozurdex	Biodegradable (PLGA)	6 months
Retisert	Non-biodegradable	2.5 years
Iluvien	Non-biodegradable	3 years
Vitrasert	Antiviral	8 months

👉 Biodegradable = no removal (VERY important)

 

ION EXCHANGE SYSTEM ✅⭐

Mechanism

• Drug binds to charged polymer

• In body → exchanged with ions (Na⁺, Cl⁻)

• Drug released

ION EXCHANGE SYSTEM ✅⭐

Key Idea

 Ion exchange → triggers drug release

 ION EXCHANGE SYSTEM

Example

• Tussionex

  • Hydrocodone + chlorpheniramine

  • Uses Pennkinetic system

AUTOINJECTORS ✅⭐

Definition

• Device delivering single dose (life-saving)

 AUTOINJECTORS ✅⭐

Features

• Spring-loaded

• Needle shielded

• Easy self-use

AUTOINJECTORS

Examples

• EpiPen

• ATNAA

INSULIN PENS (VERY IMPORTANT) ✅⭐

Structure

• Cartridge + dial

• Disposable needles

INSULIN PENS (VERY IMPORTANT) ✅⭐

Advantages

• Accurate dosing

• Easy to use

• Less pain

INSULIN PENS (VERY IMPORTANT) ✅⭐

Disadvantages

• Expensive

• Cannot mix insulins

INSULIN PENS (VERY IMPORTANT) ✅⭐

PATIENT COUNSELING

• Store unopened → refrigerator

• Assign BUD

• Never share

• Change needle every use

VAGINAL RINGS

Mechanism

• Releases hormones over 3 weeks

• Prevents ovulation

• Thickens cervical mucus

VAGINAL RINGS

Examples

• NuvaRing

• Estring

PULSE DELIVERY (CONCEPTUAL) ✅⭐

Concept

Drug released in pulses (not continuous)

PULSE DELIVERY (CONCEPTUAL) ✅⭐

Example (SMART SYSTEM)

• Device senses glucose

• Adjusts insulin release

• Uses electrical pulses to open skin

👉 Feedback-controlled system

 TERNARY SOLID DISPERSION

Definition

• Drug + 2 polymers OR polymer + surfactant

 TERNARY SOLID DISPERSION

Advantage

• ↑ Stability

• ↑ Dissolution

NEBULIZERS (COMPARE)

Ultrasonic Nebulizer vs. Vibrating Mesh Nebulizer

Ultrasonic Nebulizer

• Piezoelectric crystal

• Creates vibration → aerosol

• Uses cavitation

 

Vibrating Mesh Nebulizer

• Mesh pushes liquid through holes

• Uniform particle size

MICRONEEDLES (VERY IMPORTANT) ✅⭐

Types

• Solid → increase skin permeability

• Coated → drug on needle

• Hollow → inject drug

MICRONEEDLES (VERY IMPORTANT) ✅⭐

Key Idea

Minimally invasive drug delivery

HYDROGELS

Definition

• 3D polymer networks (hydrophilic)

HYDROGELS

Cross-linking

• Covalent bonds

• Hydrogen bonding

• Polymer entanglement

HYDROGELS

Types

• Neutral

• Anionic

• Cationic

• Ampholytic

FUTURE / RESEARCH SYSTEMS - overview

Microneedle GI Capsule

Receptor-Mediated Delivery

Microneedle GI Capsule

• Swallowed capsule

• Releases needles in intestine

• Delivers drug directly

Receptor-Mediated Delivery

• Targets tumor receptors

• ↓ side effects

• ↑ specificity