Drug delivery refers to the methods and processes of administering pharmaceutical compounds to achieve a therapeutic effect in humans or animals. The discipline has undergone major advances in recent years with the goal of improving drug efficacy, safety, and patient convenience.

New drug delivery systems are being actively researched and implemented that better control the rate and duration of drug release and targeting of specific body tissues. In this blog post, we will provide an overview of the latest advancements in drug delivery techniques and technology.

Sustained-Release Formulations

Traditional drug formulations provide an immediate release of the active pharmaceutical ingredient. This can require frequent dosing to sustain therapeutic levels over the desired timeframe. Sustained-release drug delivery systems allow for prolonged and consistent drug release over hours or days, which improves patient compliance and convenience.

Common sustained-release technologies include polymer-based matrices that slowly erode and diffuse drug over time. Tiny drug reservoirs surrounded by permeable membranes can provide zero-order release kinetics.

Implantable devices are also used, which slowly release drugs as the polymer or reservoir degrades within the body. These systems mean a single administration can maintain therapeutically effective concentrations for an extended duration.

Targeted Drug Delivery

Conventional systemic drug administration distributes drug rather nonspecifically throughout bodily tissues which can lead to unwanted side effects. Targeted drug delivery seeks to concentrate the pharmacological agent in the tissue of interest while reducing systemic exposure. This enhances safety and efficacy through increased bioavailability at target sites.

Nanoparticles loaded with drugs and coated with targeting molecules can preferentially accumulate at desired tissue locations. Strategies include targeting cancerous tumors with nanoparticles coated in tumor-specific antibodies.

Other targeting mechanisms include exploiting subtle biochemical differences in diseased tissue, using external devices to concentrate compounds locally, or designing biochemical responsiveness to local disease markers.

Transdermal Patches

Transdermal drug delivery involves adhesive patches placed on the skin which gradually deliver drugs into the systemic circulation. It protects orally administered drugs from degradation in the gastrointestinal tract while avoiding the pain and complications of injection. Transdermal administration improves user compliance relative to pills or injections.

Advanced patch engineering controls drug dispersion kinetics across layers of membranes and adhesives to modulate delivery rates. Microscopic pores or added chemical permeation enhancers promote drug diffusion across the relatively impermeable outer skin layers.

Today’s third generation patches deliver a wide range of compounds including hormones, opioids, cardiovascular drugs, and anticancer agents.

Pulsatile Release Systems

Some diseases like asthma, heart conditions and arthritis follow circadian rhythms, with symptoms worsening at specific times of the day. Pulsatile or timed-release delivery systems administer drugs according to a programmed schedule corresponding to disease rhythms rather than continuously.

Internal or external stimuli like heart rate, temperature changes or electronic alarms can trigger spikes in drug concentrations tailored to patient needs.

Coatings on tablets or capsules erode at predefined intervals to generate well-timed pharmacological pulses. This improves efficacy through synchronization with body rhythms while reducing steady drug levels and side effects.

Ocular Inserts

Delivering therapeutic agents to treat eye diseases is challenging because protective barriers limit drug permeation and tear fluid rapidly eliminates foreign substances. Ocular drug inserts are thin films placed into the eye’s cul-de-sac which improve bioavailability while causing minimal discomfort or interference with vision or eyelid movement.

Inserts allow extended drug release for treating inflammatory, infectious and glaucoma eye diseases. Soft contact lens-shaped inserts with embedded drug reservoirs further improve comfort and diffusion kinetics. Ongoing advances in polymer engineering and nanotechnology continue expanding the range of feasible ocular drugs.

Implantable Drug Pumps

Implantable drug pumps are programmable devices inserted under a patient’s skin which provide computerized drug injections in precise volumes and intervals. A catheter connects the pump to the intrathecal space surrounding the spinal cord to achieve high cerebrospinal fluid drug concentrations.

These pumps improve adherence for long-term treatment regimens where oral medications are insufficient like chronic pain, spasticity, and severe neurological disorders. The infusion parameters are wirelessly adjustable allowing physicians to optimize dosing regimens and respond to changing patient requirements.

Microneedle Arrays

The outermost skin layer called the stratum corneum blocks drugs from reaching the systemic circulation leading to poor bioavailability for topically applied compounds. Microneedle drug delivery devices contain dozens of microscopic needles less than one millimeter tall that painlessly pierce the skin’s barrier layer.

When coated on microneedles, drugs rapidly dissolve off the tiny needles’ surfaces to achieve therapeutic effects at lower doses than standard formulations. Controlled release is feasible by encapsulating compounds within microneedle tip microstructures.

This novel approach suits a range self-administered medications for diseases like osteoporosis, cancer and cardiovascular conditions.

3D Printing Pills

3D printing, also called additive manufacturing, fabricates physical objects layer-by-layer from digital files. 3D printed oral drug products create intricately shaped tablets and capsules with customized drug release characteristics.

This permits constructing complex internal geometries like honeycombs or tunnels that modify diffusion rates in ways unachievable through traditional manufacturing.

Technologies like fused deposition modeling produce drug-loaded filaments extruded according to computer-guided pathways. Inkjet printing heads deposit precise medication droplets onto powders layered according to precise digital schematics.

3D printing promises improved combination therapies and personalized medicine approaches tailored to individual patient requirements.

Bioadhesive Drug Formulations

Bioadhesives stick to mucosal membranes inside bodily orifices for prolonged periods to facilitate drug absorption at those sites. Areas like the mouth, GI tract, eyes, nasal cavities and genitourinary system provide direct absorption pathways into the bloodstream bypassing first pass liver metabolism.

Various natural and synthetic bioadhesive polymers improve drug residence time on mucosal layers. Common compounds used include chitosan, gelatin, sodium alginate, tragacanth and acrylate graft copolymers.

Optimized bioadhesives modulate stickiness, swelling viscosity and longevity on mucous surfaces. This enhances local and systemic drug concentrations increasing therapeutic efficacy.

Stimuli-Responsive Drug Carriers

Stimuli-responsive or ‘intelligent’ polymers have chains that undergo abrupt structural changes in response to small physical or chemical triggers within their vicinity. Exploiting this effect by incorporating drugs into stimuli-responsive nanoparticles enables triggered release in diseased bodily regions.

pH-sensitive polymers possess ionizable groups that protonate or deprotonate based on acidity levels yielding hydration and solubility changes that alter carrier permeability to discharge contents.

Temperature-sensitive polymer carriers experience reversible structural transitions above or below threshold heat levels. Light-activated nano-architectures degrade when exposed to specific visible or UV frequencies to initiate drug activation.

Combination Drug Delivery Systems

Combination drug therapy coadministers multiple medications formulated individually but packaged together. This improves compliance by reducing pill burden and simplifies dosage regimens.

Several drugs targeting different disease pathways can act synergistically amplifying therapeutic effects. Multi-drug incorporation onto single carriers like nanoparticles or micelles simplifies pharmacokinetics enabling synchronized biodistribution and clearance.

Future combination delivery systems will provide custom drug ratios tailored to changing long-term patient requirements. Closed-loop carriers responding to biomarkers and circulating drug concentrations using attached sensors could autonomously release and adjust relative dosages achieving truly individualized therapy.

Conclusion

Drug delivery technology has progressed enormously facilitating the emergence of novel dosage forms like sustained-release tablets, ocular inserts, transdermal patches and implantable pumps. Numerous innovative platforms harness micro and nanotechnologies alongside substantial biomaterials science advances. The sophistication of drug carrier engineering will continue evolving fairly rapidly over the next decade as precision requirements for these systems increase.

The coming years promise drug carriers capable of delivering multiple agents whose rates and ratios adaptively tune to each patient’s changing needs. Unprecedented spatial-temporal control over in vivo drug concentrations will emerge enabling durable disease remission through synergistic combination regimens fine-tuned to the dynamics of each person’s physiology.