What are the different routes of drug administration and their indications?

From the Guidelines

The most appropriate route of drug administration depends on the specific medication, patient needs, and condition being treated, with oral administration being the most common due to its convenience and safety, as seen with medications like metformin or lisinopril. When considering the administration of drugs, several factors come into play, including the properties of the drug itself, the needs and condition of the patient, and the desired onset and duration of the drug's action. The routes of administration include:

• Oral: The most common route, used for medications like metformin (500-2000mg daily) or lisinopril (5-40mg daily), due to its convenience and safety 1.
• Intravenous: Provides immediate effect and complete bioavailability, essential for emergency medications like epinephrine (0.1-0.5mg in anaphylaxis) or antibiotics in sepsis (e.g., ceftriaxone 1-2g daily) 1.
• Intramuscular: Offers intermediate absorption rates, used for vaccines or depot antipsychotics (e.g., haloperidol decanoate 50-200mg monthly).
• Subcutaneous: Works well for insulin (dosage varies by patient) or heparin (5000 units twice daily for prophylaxis), and is a preferred alternative route when oral administration is not possible, as noted in the management of cancer pain 1.
• Topical: Delivers medications directly to affected areas, minimizing systemic effects.
• Transdermal: Provides a non-invasive alternative for stable opioid requirements, such as transdermal fentanyl.
• Inhalation: Offers direct lung delivery for respiratory conditions (e.g., albuterol 2 puffs every 4-6 hours).
• Sublingual/Buccal: Bypasses first-pass metabolism for medications needing rapid absorption, like nitroglycerin (0.4mg for acute angina).
• Rectal: May be preferred by some patients and has a bioavailability similar to oral administration, with a 1:1 relative potency ratio for morphine 1. The selection of the administration route is crucial for the effective management of various conditions, considering factors such as drug solubility, patient age and consciousness, condition urgency, and the desired onset and duration of action. The optimal route of administration should prioritize patient safety, convenience, and the specific needs of their condition, as supported by the most recent and highest quality evidence 1.

From the Research

Routes of Drug Administration

The routes of drug administration are various and can be optimized to improve drug absorption and effectiveness. According to 2, a wide range of administration routes can be used, and each has its strengths and weaknesses. The choice of route depends on the drug, its target, and the release pattern required.

Types of Routes

Some of the common routes of drug administration include:

• Oral route: This is the most common route of administration, but it may not be suitable for all drugs due to first-pass metabolism, as mentioned in 3.
• Parenteral route: This route includes intravenous, intramuscular, and subcutaneous administration, and is often used for drugs that need to be absorbed quickly.
• Topical route: This route is used for drugs that need to be applied directly to the skin or mucous membranes.
• Inhalation route: This route is used for drugs that need to be absorbed through the lungs.

Factors Affecting Route Selection

The selection of a route of administration depends on several factors, including:

• The properties of the drug, such as its solubility and stability, as mentioned in 2.
• The therapeutic objective, as mentioned in 4.
• The patient's age, size, and level of organ maturity, as mentioned in 5.
• The presence of any diseases or conditions that may affect drug absorption or distribution, as mentioned in 3.

Examples of Route-Specific Administration

Some examples of route-specific administration include:

• Insulin, which is typically administered via the subcutaneous route.
• Vaccines, which are often administered via the intramuscular route.
• Asthma medications, which are often administered via the inhalation route.
• Topical creams and ointments, which are applied directly to the skin.

Importance of Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is an important aspect of drug administration, as it helps to optimize individual dosage regimens and maintain a constant concentration of the drug in the patient's bloodstream, as mentioned in 6. TDM is particularly important for drugs with narrow therapeutic ranges or marked pharmacokinetic variability.