INH — Inhalation as a Route of Drug Administration (Comprehensive Study Notes) Summary & Study Notes

📘 Overview

Inhalation (abbreviated INH) is a route of drug administration where medications are delivered to the body via the respiratory tract by breathing. This route allows drugs to reach the lungs in different physical forms and be absorbed into the bloodstream for local or systemic effects.

🧾 Definition & Key Concepts

Inhalation (INH): Delivery of medications by breathing them into the airways and lungs. This route can provide rapid onset, direct targeting of respiratory tissue, and reduced systemic side effects compared with many oral or parenteral routes.

🧪 Physical Forms of Inhaled Medications

• Gases: Pure inhalable gases such as $O_2$ (supplemental oxygen) and $N_2O$ (nitrous oxide for anesthesia). Mixtures include heliox ($He + O_2$) used in severe airflow obstruction. Delivered via masks, nasal cannula, or anesthesia machines.
• Vapors: Volatile liquids (e.g., inhalational anesthetics like halothane, isoflurane) delivered by vaporizers or steam inhalation devices.
• Aerosols (mists): Liquid medication droplets suspended in air (e.g., albuterol, ipratropium). Delivered with MDIs, nebulizers, or soft-mist inhalers.
• Dry powder: Micronized drug particles (e.g., budesonide, salmeterol) delivered by dry powder inhalers (DPIs) that are breath-activated.

🏥 Common Clinical Applications

• Asthma: Rescue therapy with SABAs (albuterol); maintenance with inhaled corticosteroids (ICS) and LABA/ICS combinations.
• COPD: LAMAs (tiotropium), LABAs, combination therapies, and triple therapy for severe disease.
• Pneumonia & Respiratory Infections: Nebulized antibiotics and mucolytics when indicated.
• Other: Cystic fibrosis, bronchiectasis, pulmonary hypertension, perioperative oxygenation, and investigational inhaled therapies for TB.

⚙️ Delivery Devices & Key Techniques

💨 Metered Dose Inhaler (MDI)

• Prepare: Shake inhaler vigorously (5–10 s) and remove cap. Prime if new or unused (>2 weeks) by releasing 2–4 test sprays.
• Technique: Exhale fully away from mouthpiece → form a tight seal (or hold 1–2 in. from mouth if instructed) → begin slow, deep inhalation and actuate canister once → inhale over 3–5 s → hold breath for 10 s → wait 30–60 s before next puff if required.
• Tips: Use a spacer/holding chamber to improve coordination and lung deposition. Rinse mouth after corticosteroid inhalers to reduce oral candidiasis.

🌬️ Dry Powder Inhaler (DPI)

• Key difference: Requires a strong, fast inhalation (do not use a spacer).
• Technique: Load dose per device instructions → exhale fully away from device (never into it) → seal lips around mouthpiece → inhale forcefully and deeply → hold breath for ~10 s.
• Tips: Keep device dry; moisture can clog powder.

💧 Nebulizer

• When to use: Young children, severe exacerbations, patients unable to use MDI/DPI, or when high/continuous dosing is needed.
• Steps: Prepare medication and diluent (typical volume 3–5 mL) → assemble nebulizer and tubing → position patient upright (45–90°) → use mouthpiece or snug mask → turn on compressor and instruct to breathe normally with occasional deep breaths → treatment lasts ~10–15 min until mist stops.
• Aftercare: Rinse nebulizer cup and mouthpiece, air dry, and document.

✅ Advantages of the Inhalation Route

• Large surface area of the lungs (70–140 m²) enables efficient absorption.
• Rapid onset: effects often within 5–15 minutes for rescue drugs.
• Bypasses first-pass hepatic metabolism, increasing bioavailability for some drugs.
• Lower doses are often effective, reducing systemic adverse effects.
• Direct targeting of airway tissues for localized treatment.
• Non-invasive and generally well tolerated.

⚠️ Disadvantages & Limitations

• Low lung deposition: Only ~10–40% of medication may reach the lungs; much is deposited in the oropharynx and swallowed.
• Technique-dependent: Up to 60% of patients use inhalers incorrectly, reducing efficacy.
• Device maintenance: Requires proper cleaning, storage, and sometimes power (nebulizers).
• Local side effects: Corticosteroids can cause oral candidiasis, hoarseness, and throat irritation.
• Formulation constraints: Not all drugs can be made into stable, safe inhaled forms due to particle size and tolerability requirements.
• Mucociliary clearance: Natural lung defenses may clear medication before full absorption.

👩‍⚕️ Nursing Responsibilities

• Verify the six rights: right patient, drug, dose, route, time, and documentation.
• Assess respiratory status: RR, SpO₂, lung sounds, work of breathing, and patient symptoms before and after administration.
• Evaluate technique: Observe and correct inhaler technique; check inspiratory flow for DPI use and need for a spacer.
• Provide patient education: Demonstrate technique, have patient return-demonstrate, give written instructions, and explain when to seek help.
• Monitor effects: Therapeutic response and adverse reactions (tremors, tachycardia, thrush) and reassess vital signs.
• Document: Medication details (name, dose, route, device type), pre/post assessments, technique observed, education provided, and patient response.

📝 Step-by-Step Nursing Procedure (MDI Summary)

1. Verify order and perform hand hygiene.
2. Assess baseline respiratory status (RR, SpO₂, lung sounds).
3. Prepare MDI: remove cap, shake 5–10 times, attach spacer if recommended.
4. Instruct patient to exhale completely away from device.
5. Position inhaler, actuate while patient inhales slowly over 3–5 s.
6. Hold breath for 10 s, then exhale slowly.
7. Wait 30–60 s between puffs if multiple doses ordered.
8. Rinse mouth after corticosteroid use and document the procedure and response.

⚕️ Complications & Side Effects

• Local: oral candidiasis (thrush), hoarseness/dysphonia, throat irritation, cough. Prevention includes spacer use and mouth rinsing after steroids.
• Systemic: tremors, tachycardia, hypokalemia with high-dose β2-agonists; adrenal suppression with high-dose ICS (use lowest effective dose).
• Equipment-related: contamination, clogging, improper dosing from technique errors. Regular cleaning and inspection are essential.
• When to notify provider: paradoxical bronchospasm, severe/persistent side effects, lack of improvement, or worsening respiratory status.

🗂️ Documentation & Evaluation

Document: drug name, dose, route, time, device type, lot/expiry when relevant; pre/post vital signs and lung sounds; patient's subjective response; technique observed and education given. Evaluate therapeutic effectiveness, patient tolerance, and mastery of technique.

🔑 Key Takeaways

• Inhalation is a vital route for rapid, targeted respiratory therapy in asthma, COPD, and other pulmonary conditions.
• Technique is critical; ongoing education and technique assessment greatly improve outcomes.
• Nurses play an essential role in assessment, administration, education, monitoring, and documentation to ensure safe and effective inhalation therapy.