Advantage And Disadvantage Of Pulmonary/Inhalation Route Of Drug Administration

Lung or pulmonary is a very attractive target for drug delivery. It provides direct access to disease in the treatment of respiratory diseases, while providing an enormous surface area and a relatively low enzymatic, controlled environment for systemic absorption of medications. As a major port of entry, the lung has evolved to prevent the invasion of unwanted airborne particles from entering into the body. Airway geometry, humidity, mucociliary clearance and alveolar macrophages play a vital role in maintaining the sterility of the lung and consequently are barriers to the therapeutic effectiveness of inhaled medications. In addition, a drug's efficacy may be affected by where in the respiratory tract it is deposited, its delivered dose and the disease it may be trying to treat.

Pulmonary and inhalation route

Inhaled medications have been available for many years for the treatment of lung diseases and are widely accepted as being the optimal route of administration of first-line therapy for asthma and chronic obstructive pulmonary diseases. In recent years, the lung has been studied as a possible route of administration for the treatment of systemic diseases, such as diabetes mellitus.

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For the lungs to be the target organ or a route of administration, the appropriate amount of drug must be deposited past the oropharyngeal region to achieve therapeutic effectiveness. The site of deposition, that is on central or peripheral airways, and whether the distribution of the inhaled drug is uniform or non-uniform may also play a role in an inhaled drug's effectiveness.

Advantages Of Pulmonary/Inhalation Route Of Drug Administration

1. Deliver high drug concentrations directly to the disease site

2. A noninvasive ‘needle-free’ delivery system

3. Dose required is very less, so systemic toxicity is minimized

4. Suitable for a wide range of substances from small molecules to very large proteins

5. Rapid clinical response

6. Enormous absorptive surface area (100 m2) and a highly permeable membrane (0.2–0.7 µm thickness) in the alveolar region

7. Bypass the barriers to therapeutic efficacy, such as poor gastrointestinal absorption and first-pass metabolism in the liver

8. Large molecules with very low absorption rates can be absorbed in significant quantities; the slow mucociliary clearance in the lung periphery results in prolonged residency in the lung

9. Achieve a similar or superior therapeutic effect at a fraction of the systemic dose. For example, oral salbutamol 2–4 mg is therapeutically equivalent to 100–200 µg by MDI

10. A less harsh, low enzymatic environment that is devoid of hepatic first-pass metabolism

11. Reproducible absorption kinetics. Pulmonary delivery is independent of dietary complications, extracellular enzymes and interpatient metabolic differences that affect gastrointestinal absorption

12. Amount of drug administered can be regulated

Read Also: Overview Of Pulmonary/Inhalation Route Of Drug Administration

Disadvantages Of Pulmonary/Inhalation Route Of Drug Administration

1. Local irritation may cause increased respiratory secretions and bronchospasm

2. Patients may have difficulty regulating dose

3. Some patients may have difficulty using inhalers

4. The transport of drug to the site of action is not guaranteed