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

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Inhalation (INH)

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A route of drug administration where medications are delivered to the body through the respiratory tract by breathing. Drugs enter the lungs in various physical forms and can be absorbed into the bloodstream or act locally in the airways. Abbreviation: INH.

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Gases

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Pure gaseous substances delivered in inhalable form for therapeutic use. Examples include oxygen ($O_2$) for supplemental therapy and nitrous oxide ($N_2O$) for anesthesia, typically given via masks or cannulas.

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Vapors

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Volatile liquids that evaporate at room temperature and are inhaled as therapeutic agents or adjuncts. Examples include volatile anesthetics and essential oils, delivered via vaporizers, steam inhalers, or nebulizers.

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Aerosols

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Liquid medication droplets suspended in air as a mist for inhalation therapy. Common aerosol medications include albuterol and nebulized antibiotics, administered via MDIs, nebulizers, or soft mist inhalers.

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Dry Powder

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Micronized drug particles formulated as a dry powder for inhalation, activated by the patient's inspiratory flow. Examples include salmeterol and budesonide, delivered using dry powder inhalers (DPIs) that require forceful, rapid inhalation.

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Metered-Dose Inhaler

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A pressurized device that delivers a measured dose of aerosolized medication with each actuation. Proper technique involves shaking, coordinated actuation with slow deep inhalation, a $10$ second breath-hold, and rinsing after corticosteroid use to prevent oral thrush.

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Dry Powder Inhaler

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A breath-activated device that delivers micronized powder particles when the patient inhales forcefully and rapidly. DPIs do not use spacers and require strong inspiratory flow to disperse the powder; patients must not exhale into the device to avoid moisture clogging.

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Nebulizer

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A device that converts liquid medication into a fine mist for spontaneous breathing or assisted inhalation. Nebulizers are useful for infants, patients with coordination or cognitive issues, severe disease, or when high-dose or continuous delivery is required, typically taking about $10$–$15$ minutes per treatment.

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Oxygen Therapy

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Administration of supplemental oxygen (often $O_2$) to correct hypoxemia and support tissue oxygenation. Delivered via nasal cannula, masks, or ventilatory support depending on flow requirements and patient condition.

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Alveolar Absorption

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The process by which inhaled drugs pass across the alveolar-capillary membrane into the systemic circulation. Because alveoli have thin membranes and rich blood supply, this site enables rapid absorption and onset of action for many inhaled medications.

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Large Surface Area

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The lungs provide an extensive absorptive surface, approximately $70-140 m^2$, which promotes efficient drug uptake. This large area contributes to rapid systemic absorption and effective local drug delivery to the respiratory tract.

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Rapid Onset

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Inhalation allows medications to reach the bloodstream quickly, often producing effects within $5-15$ minutes. This rapid onset is essential for rescue therapies in acute asthma or COPD exacerbations.

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Bypass First-Pass

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Drugs absorbed via the lungs enter systemic circulation directly, avoiding hepatic first-pass metabolism. This increases bioavailability compared with many oral drugs and permits lower dosing for some agents.

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Lower Dose Requirement

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Direct delivery to the lungs and high local bioavailability often allow effective therapy at smaller doses than oral administration. Lower systemic exposure reduces systemic side effects and can reduce cost.

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Direct Targeting

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Inhalation delivers medication straight to the respiratory tract for localized treatment of airway diseases. This targeted approach minimizes systemic exposure while maximizing therapeutic effect in the lungs.

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Non-invasive Route

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Inhalation is a non-invasive administration method that is generally well tolerated by patients. It is suitable for those who cannot take oral medications or who wish to avoid injections.

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Limited Deposition

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Only a fraction of medication from conventional inhalation devices reaches the lungs, typically $10-40\%$, with the remainder depositing in the oropharynx or being swallowed. This reduces efficiency, risks inconsistent dosing, and can increase systemic absorption from swallowed drug.

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Technique Errors

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Many patients—up to $60\%$—use inhaler devices incorrectly, which markedly reduces drug delivery and effectiveness. Common errors include poor coordination with MDIs, inadequate breath-hold, exhaling into the device, and failing to shake the inhaler.

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Equipment-Dependent

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Inhalation therapy requires specific devices (MDIs, DPIs, nebulizers) that must be maintained, cleaned, and replaced as needed. Device malfunction, contamination, cost, and power requirements (for nebulizers) can limit effectiveness and access.

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Mucociliary Clearance

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The lung’s natural defense mechanism that moves mucus and trapped particles out of the airways, which can reduce drug residence time. Rapid clearance, especially in central airways, may limit absorption of inhaled medications unless formulations and particle sizes are optimized.

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Local Side Effects

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Adverse effects at the administration site include oral candidiasis (thrush), hoarseness, throat irritation, cough, and paradoxical bronchospasm. Many local steroid-related effects can be reduced by using a spacer and rinsing the mouth after inhaled corticosteroid use.

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Systemic Effects

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Systemic adverse effects of inhaled medications can occur, particularly with high doses or poor technique; examples include tremors, tachycardia, palpitations, hypokalemia, and potential adrenal suppression from corticosteroids. Monitoring and using the lowest effective dose help minimize these risks.

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Nursing Responsibilities

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Nurses must verify medication rights, assess respiratory status, evaluate inhaler technique, provide education, monitor therapeutic and adverse effects, and document care. They play a central role in ensuring correct device use and optimizing treatment outcomes.

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MDI Procedure

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A stepwise MDI technique includes shaking the canister, testing if unused, exhaling, coordinating actuation with slow deep inhalation, holding breath for $10$ seconds, and waiting $30-60$ seconds between puffs if repeating. For corticosteroids, patients should rinse and spit after use to prevent oral thrush.

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DPI Technique

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DPI use requires loading the dose per device instructions, exhaling away from the device, sealing lips, and inhaling forcefully and deeply to disperse powder particles. DPIs should not be used with a spacer and require adequate inspiratory flow to be effective.

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Nebulizer Procedure

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Nebulizer administration involves preparing and assembling the medication cup and tubing, positioning the patient upright, ensuring a snug mask or mouthpiece fit, turning on the compressor, and allowing normal breathing with occasional deep breaths until misting stops. After treatment, equipment should be rinsed, air-dried, stored, and the administration documented.

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Common Conditions

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Inhalation therapy is used for asthma, COPD, pneumonia (including nebulized antibiotics), tuberculosis (including DOT and investigational inhaled antibiotics), cystic fibrosis, bronchiectasis, pulmonary hypertension, and respiratory distress. Choice of medication and device depends on disease, age, and ability to use devices.

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Documentation

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Essential documentation includes drug name, dose, route, time, device type, lot/expiration, pre- and post-assessment vitals and lung sounds, patient response, technique observed, education provided, and signature. Accurate records support continuity of care, evaluation of therapeutic effectiveness, and reporting of concerns.

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Patient Education

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Education includes demonstrating correct device technique, observing return-demonstration, providing written instructions, explaining rationale and warning signs, and advising when to seek help. Regular review and reinforcement improve adherence and clinical outcomes.

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Complications

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Complications range from local effects (thrush, hoarseness, cough, paradoxical bronchospasm) to systemic effects (tremors, tachycardia, hypokalemia, adrenal suppression) and equipment issues (contamination, improper dosing). Nurses should know when to stop therapy and notify the provider for severe or persistent reactions.

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Key Takeaways

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Inhalation provides rapid onset and localized treatment for respiratory diseases but depends heavily on correct technique and device selection. Nurses are essential for assessment, education, administration, monitoring, and documentation to ensure safety and therapeutic effectiveness.