Routes of Delivery

Routes of delivery refer to the various methods by which substances, such as drugs or therapeutic agents, are introduced into the body to achieve a desired effect. These routes play a pivotal role in determining how quickly and efficiently a substance is absorbed, distributed, and metabolized within the body. The choice of a specific delivery route is influenced by factors like the nature of the substance, the target organ or system, and the intended therapeutic outcome.

Figure 1. Classification of routes of drugs administration.Figure 1. Classification of routes of drugs administration.(Nunes D, et al.; 2022)

Common routes of delivery include oral/sublingual, intramuscular, intravenous, rectal, subcutaneous, auricular, inhalation/nasal, intraocular, peritoneal, internal administration (such as intrathecal or intraventricular injections), topical, and vaginal. Each route has its own set of advantages and limitations, guiding healthcare professionals in selecting the most appropriate method based on the specific characteristics of the substance and the medical condition being treated. Understanding these routes is crucial for optimizing the effectiveness of therapeutic interventions while minimizing potential side effects or complications.

Understanding Delivery Routes

Nanoparticles can be delivered into the body through various routes, each tailored to specific medical requirements. Oral/sublingual delivery involves administering nanoparticles through oral dosage forms, like tablets or liquids, for absorption in the gastrointestinal tract. Sublingual delivery, on the other hand, places nanoparticles under the tongue for swift absorption through mucous membranes. Intramuscular and subcutaneous deliveries entail injecting nanoparticles directly into muscle tissue or beneath the skin, respectively. These routes are ideal for sustained release formulations, providing controlled release over an extended period. Intravenous delivery involves direct injection into veins, ensuring rapid entry into circulation for immediate and precise distribution. Rectal delivery, through insertion into the rectum, is useful for drugs bypassing hepatic metabolism. Auricular delivery utilizes the ear's skin for transdermal nanoparticle absorption, beneficial for ear-related conditions. Inhalation/nasal delivery targets the respiratory system, administering nanoparticles through inhalation or nasal sprays for lung or systemic effects. Intraocular injection places nanoparticles directly into the eye, crucial for treating ocular diseases while managing localized effects. Peritoneal delivery injects nanoparticles into the peritoneal cavity, suitable for cancer treatments with direct exposure to abdominal organs. Internal administration covers diverse routes like intrathecal or intraventricular injections, vital for delivering nanoparticles to the central nervous system, overcoming barriers like the blood-brain barrier. Topical administration involves applying nanoparticles directly to the skin for localized effects, addressing skin disorders or cosmetic purposes. Vaginal administration, a specialized route, delivers nanoparticles to the reproductive tract for contraception, fertility treatments, or managing gynecological conditions.

Characteristics of Delivery Routes

Each delivery route has distinct characteristics influencing the absorption, distribution, and overall effectiveness of a substance within the body. Here's a brief overview of the characteristics of various delivery routes:

Oral/Sublingual Delivery:

Absorption: Through the gastrointestinal tract for oral, under the tongue for sublingual.

Speed: Variable absorption rates, affected by gastrointestinal conditions.

Advantages: Convenient, non-invasive.

Limitations: Potential for degradation in the digestive system.

Intramuscular Delivery:

Administration: Injection into muscle tissue.

Speed: Moderate, allowing for sustained release.

Advantages: Suitable for sustained-release formulations.

Limitations: Limited volume of administration.

Intravenous Delivery:

Administration: Direct injection into veins.

Speed: Rapid, immediate systemic distribution.

Advantages: Precise and rapid onset of action.

Limitations: Invasive, risk of complications.

Rectal Delivery:

Administration: Insertion into the rectum.

Speed: Variable, avoiding first-pass metabolism.

Advantages: Bypasses hepatic metabolism.

Limitations: Patient acceptance, variability in absorption.

Subcutaneous Delivery:

Administration: Injection beneath the skin.

Speed: Moderate, suitable for sustained release.

Advantages: Convenient, suitable for self-administration.

Limitations: Limited volume, potential for local reactions.

Auricular Delivery:

Administration: Transdermal delivery through the ear.

Speed: Variable, depending on skin permeability.

Advantages: Potential for targeted local effects.

Limitations: Limited surface area, variability in absorption.

Inhalation/Nasal Delivery:

Administration: Aerosols, inhalers, or nasal sprays.

Speed: Rapid absorption in the respiratory system.

Advantages: Quick onset, suitable for respiratory conditions.

Limitations: Variable absorption, potential irritation.

Intraocular Injection:

Administration: Direct injection into the eye.

Speed: Localized effects within the eye.

Advantages: Direct treatment of ocular conditions.

Limitations: Risk of infection, requires precision.

Peritoneal Delivery:

Administration: Injection into the peritoneal cavity.

Speed: Direct exposure to abdominal organs.

Advantages: Localized effects for certain conditions.

Limitations: Invasive, potential for complications.

Internal Administration (Intrathecal/Intraventricular):

Administration: Injection into the central nervous system.

Speed: Direct delivery to the brain or spinal cord.

Advantages: Overcomes blood-brain barrier.

Limitations: Invasive, potential for complications.

Topical Administration:

Administration: Applied directly to the skin.

Speed: Localized effects on the skin surface.

Advantages: Targeted for dermatological conditions.

Limitations: Limited systemic absorption.

Vaginal Administration:

Administration: Delivery to the reproductive tract.

Speed: Localized effects in the vagina.

Advantages: Suitable for gynecological conditions.

Limitations: Patient acceptance, potential for irritation.

Application Areas of Delivery Routes

Oral/Sublingual Delivery Application Areas: Common for systemic drug delivery, vitamins, and pain relievers.

Intramuscular Delivery Application Areas: Vaccines, antibiotics, certain hormones.

Intravenous Delivery Application Areas: Emergency situations, chemotherapy, blood transfusions.

Rectal Delivery Application Areas: Treatment of nausea, certain medications in children.

Subcutaneous Delivery Application Areas: Insulin, growth hormones, some vaccines.

Auricular Delivery Application Areas: Localized treatment for ear infections, ear pain.

Inhalation/Nasal Delivery Application Areas: Respiratory conditions (asthma, COPD), nasal allergies.

Intraocular Injection Application Areas: Treatment of ocular conditions like macular degeneration.

Peritoneal Delivery Application Areas: Chemotherapy for abdominal cancers, certain infections.

Internal Administration (Intrathecal/Intraventricular) Application Areas: Neurological conditions, spinal cord disorders.

Topical Administration Application Areas: Dermatological conditions, skin infections.

Vaginal Administration Application Areas: Contraceptives, treatment of vaginal infections.


  1. Nunes D, et al.; Polymeric Nanoparticles-Loaded Hydrogels for Biomedical Applications: A Systematic Review on In Vivo Findings. Polymers (Basel). 2022, 14(5):1010.
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