Study guide: Drug Administration Routes

📋 Course Outline

1. Parenteral Routes and Dosage Forms
2. Intravenous Injection and Infusion
3. Subcutaneous and Intramuscular Injection
4. Specialized Injection Routes
5. Oral Route and Dosage Forms
6. Buccal Administration
7. Topical and Transdermal Routes
8. Rectal and Vaginal Routes
9. Inhalation and Nasal Routes
10. Eye Products and Instillation
11. Ear Drops

📖 1. Parenteral Routes and Dosage Forms

★ Must-know

📌 Parenteral administration includes intravenous injection into systemic circulation, subcutaneous injection into the tissue beneath the skin, and intramuscular injection into muscle.

Further detail

• Injection dosage forms may be supplied as powders that require reconstitution before use, and injection preparations must be sterile.

📖 2. Intravenous Injection and Infusion

★ Must-know

📌 An intravenous injection gives a small volume rapidly at one time, whereas an intravenous infusion gives a large volume slowly at a constant rate.

• Intravenous administration provides a quick response and delivers the entire dose to the bloodstream, giving 100% bioavailability.

Further detail

• During an IV infusion, fluid moves by gravity, and its flow rate depends on fluid characteristics and pressure determined by the height of the infusion above the patient.

• Intravenous administration can be used when the oral route is unavailable and to deliver drugs to an unconscious patient, but it requires trained personnel and a suitable vein and cannot administer water-in-oil emulsions or suspensions.

• IV fluids are commonly administered through a superficial vein on the back of the hand or at the inner elbow; the subclavian vein is preferred for large fluid volumes.

📖 3. Subcutaneous and Intramuscular Injection

🔑 Key Concepts & Definitions

• Subcutaneous injection: Places aqueous solutions, oil solutions, or suspensions into the loose connective and adipose tissue immediately beneath the skin.
• Intramuscular injection: Places aqueous solutions, oil solutions, or suspensions directly into relaxed muscle.

★ Must-know

• Intramuscular injections can accommodate up to 2 ml, a larger volume than subcutaneous injections, and can produce a faster onset of action than subcutaneous injections.

Further detail

📌 Subcutaneous absorption is slower than direct entry into the blood by intravenous administration because the drug must cross the capillary endothelium and its basement membrane before reaching the blood.

• Subcutaneous injections can be self-administered, as with insulin, and absorption is slow but usually complete.

• Subcutaneous injections can be painful, may cause lipohypertrophy or lipoatrophy, and typically do not exceed 1 ml.

• Common subcutaneous injection sites are:

  • the abdomen
  • the upper back
  • the upper arms
  • the lateral upper hips

• Intramuscular injections require trained personnel, and the injection site influences drug absorption.

• Intramuscular sites and their common uses are: gluteal muscle for larger volumes in adults, deltoid muscle for rapid absorption, vastus lateralis for infants and small children

📖 4. Specialized Injection Routes

📝 Essential Points

• An intradermal injection places about 0.1 ml between the epidermis and dermis, is absorbed slowly, and is often used for allergy or immunity diagnostic tests.

📌 Intra-arterial injection can target an organ or tissue supplied by the artery, but rapid arterial blood flow disperses the drug quickly and technical difficulties restrict this route.

• Intracardiac injections are aqueous solutions given in emergencies directly into a ventricle or cardiac muscle for a local effect.

• Intraspinal injections are aqueous solutions given in volumes under 20 ml into specific areas of the spinal column and are categorized as subarachnoid or epidural injections.

• Intra-articular injections place an aqueous solution or suspension into the synovial fluid of a joint cavity and are often used to administer anti-inflammatory agents locally.

📖 5. Oral Route and Dosage Forms

🔑 Key Concepts & Definitions

• First-pass effect: Occurs when orally absorbed drugs travel through the liver before reaching general circulation, allowing hepatic metabolism to reduce drug effect and sometimes requiring a higher dose.

★ Must-know

📌 The oral route can produce a local effect, such as antacid treatment of the stomach or laxative treatment of constipation, or a systemic effect after gastrointestinal absorption and delivery to sites of action.

📌 Oral administration is simple, self-administered, safe, convenient, and inexpensive, but its onset is relatively slow, gastrointestinal absorption may be irregular, and gastrointestinal enzymes can destroy some drugs.

Further detail

• Oral dosage forms include:

  • solutions
  • suspensions
  • emulsions
  • tablets
  • hard-shell capsules
  • soft-shell capsules
  • granules
  • powders

• Calcium in antacids can chelate tetracycline and reduce its absorption.

• Food slows the absorption of penicillins, and food and gastrointestinal motility can affect drug absorption.

• Liquid oral dosage forms are easier to swallow and readily absorbed, whereas solid oral dosage forms are less bulky, easier to carry, more microbiologically and chemically stable, and can provide accurate dosing or mask unpleasant taste with coatings.

• Enteric-coated tablets are used for drugs degraded by gastric juice or irritating to the gastric mucosa, and indigestion remedies taken at the same time can change stomach pH and cause premature coating breakdown.

• Sustained-release tablets use a surrounding polymer to retard drug release and should be swallowed whole rather than chewed.

📖 6. Buccal Administration

★ Must-know

📌 Buccal administration can provide rapid absorption, avoid first-pass metabolism, benefit from the relatively neutral mouth pH, and be used in unconscious or vomiting patients, but holding the dose in the mouth is inconvenient and only small doses fit.

Further detail

📌 Buccal administration can produce a local effect, as with a sore-throat lozenge, or a systemic effect, as with nitroglycerine for angina.

• Saliva facilitates drug dissolution, and the highly vascular tongue and buccal cavity facilitate absorption.

• Buccal dosage forms include:

  • buccal tablets
  • lozenges
  • pastilles

💡 Memory Hook

Buccal absorption bypasses the liver; swallowed drug follows the oral route and first-pass metabolism.

📖 7. Topical and Transdermal Routes

★ Must-know

📌 Transdermal drugs cross the skin to produce systemic effects, avoid first-pass metabolism and digestive juices, and are generally limited to potent drugs because skin permeability is usually inadequate.

Further detail

• Topical dosage forms include:

  • lotions
  • liniments
  • ointments
  • pastes
  • creams
  • gels
  • paints
  • collodions
  • powders
  • irrigation solutions

• A transdermal patch delivers a controlled dose of drug over a specified time period.

💡 Memory Hook

Topical treatment is usually local; transdermal delivery crosses the skin for systemic action.

📖 8. Rectal and Vaginal Routes

★ Must-know

📌 The rectal route can be used when oral administration is unsuitable, including vomiting, unconsciousness, dysphagia, or difficulty cooperating, and most rectal venous drainage enters general circulation directly, reducing first-pass effect; absorption is nevertheless irregular and unpredictable and the route is less convenient than oral administration.

Further detail

📌 Rectal preparations can act locally, as in hemorrhoids or constipation, or systemically, as with paracetamol for fever or diazepam for epilepsy.

• Rectal dosage forms include suppositories and enemas.

• Vaginal dosage forms include:
  • pessaries
  • tablets
  • capsules
  • solutions
  • sprays
  • creams

📖 9. Inhalation and Nasal Routes

📝 Essential Points

📌 Inhaled drugs can produce local effects, such as bronchodilation in asthma or relief of nasal congestion, or systemic effects, such as general anesthesia.

• Inhalation dosage forms include:
  • inhalations
  • aerosols
  • powders

📌 Inhalation for local effects can require a much smaller dose than oral administration and reduce side effects, while lung blood flow and surface area enable very rapid absorption for systemic effects.

📌 Inhalation requires special techniques, and particles larger than 20 microns impact in the mouth and throat rather than proceeding further.

• 🔄 Use an aerosol inhaler in this sequence:
  1. Remove the cap and shake the canister thoroughly.
  2. Hold the canister upright and breathe out fully.
  3. Place the mouthpiece between the lips.
  4. Fire the inhaler while inhaling slowly and deeply.
  5. Hold the breath for 10 seconds or as long as comfortable.
  6. Wait at least 1 minute before taking a second dose.

📌 The nasal route traditionally produces local effects, such as decongestion or treatment of allergic rhinitis, but can also produce systemic effects, such as desmopressin treatment of diabetes insipidus, because nasal vascularity promotes absorption and the route avoids first-pass metabolism.

• Nasal dosage forms include nasal sprays and nasal drops.

📖 10. Eye Products and Instillation

★ Must-know

• Eye products are used for local effects such as treating eye infection or allergy, are available as drops or ointments, must be sterile, and should be discarded 4 weeks after opening.

Further detail

• 🔄 Instill eye drops in this sequence:

  1. Wash hands thoroughly.
  2. Tilt the head back and pull down the lower lid to form a pocket.
  3. Hold the dropper close to the eye without touching it.
  4. Look up and squeeze one drop into the pocket.
  5. Close the eye for 2 to 3 minutes without blinking or squeezing.
  6. Press gently on the tear duct.
  7. Wipe away excess liquid and repeat the instillation steps if needed.

• 🔄 Apply eye ointment in this sequence:

  1. Wash hands.
  2. Tilt back the head.
  3. Pull down the cheek to form an eyelid pouch.
  4. Position the tube above the eye and look up.
  5. Squeeze a 1/4- to 1/2-inch ribbon into the pouch without touching the eye.
  6. Close the eye gently for 1 to 2 minutes.

📌 When eye drops and eye ointment are both used, administer the drops 10 minutes before the ointment; vision may be temporarily blurred after ointment application.

💡 Memory Hook

For eye drops: wash, form a lower-lid pocket, instill, close, then press the tear duct.

📖 11. Ear Drops

📝 Essential Points

• Ear drops are used for local effects such as ear infections or earwax.

• 🔄 Administer ear drops in this sequence:
  1. Warm the bottle in the hands and shake it.
  2. Draw liquid into the dropper.
  3. Lie on the side or tilt the head with the affected ear upward.
  4. For adults, hold the earlobe up and back; for children, hold it down and back.
  5. Instill the correct number of drops.
  6. Keep the head tilted for several minutes.
  7. Straighten the head and wipe away excess liquid.