The route and dosage form decide how much drug reaches the circulation, how fast, and for how long. Choosing or changing a route changes the pharmacokinetics (Topic 1): bioavailability, onset, peak, and duration. A dose that is correct for one route can be dangerous by another, so route is one of the core rights of medication administration, and a route change always needs a prescriber order.

Routes compared

Onset order for a typical drug, from fastest: IV > inhalation > sublingual > IM > SC > oral > transdermal (with exceptions for specific drugs and formulations).

Oral dosage forms

Parenteral forms: solutions, suspensions (never IV unless labeled for IV), emulsions (propofol, lipid emulsion), powders for reconstitution (check diluent, volume, and stability), depot/long-acting injections (medroxyprogesterone every 3 months, long-acting antipsychotics).

Other forms: metered-dose inhaler (MDI), dry-powder inhaler (DPI), nebulizer solution; transdermal patches (fentanyl, nitroglycerin, clonidine, estrogen, nicotine, scopolamine, buprenorphine); suppositories; eye drops and ointments; nasal sprays (including naloxone and intranasal midazolam); vaginal rings.

Examples of route-specific drugs

• Nitroglycerin: sublingual for acute angina (bypasses first-pass); patch or ointment for prevention; IV for acute coronary syndrome or acute heart failure
• Insulin: SC for routine use; only regular insulin (and some specific products per label) is given IV
• Epinephrine: IM into the mid-outer thigh for anaphylaxis using 1 mg/mL; IV bolus in cardiac arrest uses 0.1 mg/mL (1 mg/10 mL); outside arrest, IV only as a diluted, monitored infusion. Never give 1 mg/mL undiluted IV push — a common wrong-concentration and wrong-route error
• Potassium chloride: oral or diluted IV infusion; never IV push or IM
• Vitamin K (phytonadione): IM for newborn prophylaxis; oral for most non-urgent warfarin reversal in adults; slow, diluted IV infusion for serious bleeding (with 4-factor prothrombin complex concentrate). Boxed warning: severe hypersensitivity reactions with IV and IM use — infuse slowly and monitor. SC absorption is erratic and not preferred; IM risks hematoma in adults with coagulopathy
• Vincristine and other vinca alkaloids: IV only — fatal if given intrathecally; dispensed in a minibag to prevent syringe-to-spinal errors
• Enoxaparin: SC (IV in selected cardiac settings); not IM

• Oral route: not for clients who are NPO, vomiting, unconscious, without a gag reflex, or with new dysphagia (hold and seek a swallow evaluation)
• IM route: avoid with thrombocytopenia or therapeutic anticoagulation unless the drug has no alternative; poor absorption in shock or hypothermia; limited muscle mass in infants and older adults
• SC route: unreliable in shock, severe edema, or poor perfusion — IV insulin in diabetic ketoacidosis
• Rectal route: avoid in neutropenia, recent rectal or prostate surgery, and active rectal bleeding
• Transdermal: fentanyl patches only in opioid-tolerant clients; avoid heat sources (heating pads, electric blankets, hot tubs, fever increases absorption); remove metal-containing patches before MRI
• Enteral tubes: some drugs bind to feeds or tubing (phenytoin, warfarin, levothyroxine, fluoroquinolones) — follow pharmacy guidance
• Wrong-route prevention: enteral syringes and connectors that do not fit IV lines (ISO 80369-3, "ENFit"); label all lines; never draw oral liquids into IV syringes

Listed in priority order.

1. Verify the route is correct and ordered before giving; clarify any order that lacks a route or uses an ambiguous abbreviation
2. IV safety
   • Check IV patency and blood return before giving vesicants or push drugs
   • Give IV push at the rate in the drug reference (e.g., phenytoin no faster than 50 mg/min in adults; furosemide slowly over 1–2 minutes at usual doses, and no faster than 4 mg/min for high-dose infusions, to prevent ototoxicity)
   • Stop the infusion at the first sign of infiltration or extravasation; follow the extravasation protocol (disconnect, aspirate if ordered, elevate, specific antidote such as phentolamine for norepinephrine extravasation)
   • Use infusion pumps for high-alert drugs
3. Match the dosage form to the client
   • Check before crushing; ask the pharmacist for a liquid or alternative if the client cannot swallow an ER or EC product
   • Shake suspensions; use oral syringes for small volumes
4. Choose sites correctly: IM — ventrogluteal preferred in adults, vastus lateralis in infants, deltoid for small volumes (≤ 1 mL); SC — rotate within the abdomen and other areas; insulin and heparin sites are not massaged
5. Transdermal: remove the old patch before applying a new one; apply to clean, dry, hairless skin; rotate sites; label with date and time; fold used fentanyl patches sticky sides together and dispose of them per policy
6. Monitor effect according to the expected onset: reassess pain about 15–30 minutes after IV opioids and about 30–60 minutes after oral opioids; expect delayed onset with patches
7. Route conversion: doses differ between routes (oral vs IV); a route change requires a new order and often a new dose

• Swallow extended-release and enteric-coated tablets whole; do not crush, chew, or split unless the label or pharmacist says it is safe
• Shake suspensions; use the dosing device that comes with the medicine
• Sublingual nitroglycerin: let it dissolve under the tongue; keep tablets in the original dark glass container
• Inhalers: learn the correct technique for your device (MDI slow and deep with a spacer; DPI fast and forceful, do not shake); rinse after corticosteroid inhalers
• Patches: one patch at a time; avoid heating pads, saunas, and hot tubs; report fever; keep new and used patches away from children and pets
• Self-injection: rotate sites; dispose of needles in a puncture-resistant container
• Eye drops: press on the inner corner of the eye for 1–2 minutes after instilling; wait about 5 minutes between different drops

• Dose dumping from crushed extended-release opioids, calcium channel blockers, or antiepileptics can cause overdose — monitor sedation, blood pressure, and heart rate; naloxone for opioids
• Fentanyl patch toxicity: remove the patch, stimulate, support breathing, give naloxone; the drug keeps absorbing from the skin depot for many hours after removal, so observe for at least 24 hours
• Wrong-route errors: oral liquid given IV (embolism, sepsis); vincristine intrathecally (fatal neurotoxicity); concentrated potassium IV push (cardiac arrest) — these are "never events"
• Extravasation: stop infusion, notify, follow protocol; delayed necrosis may appear days later
• Accidental pediatric exposure to patches or adult tablets: a single fentanyl patch or a few adult tablets can kill a small child — secure storage and proper disposal prevent this
• Systemic effects from topical products: timolol eye drops (bradycardia, bronchospasm); lidocaine on large areas (seizures, dysrhythmias); topical salicylates

• IV = fastest, 100% bioavailable, cannot be recalled
• Sublingual, buccal, transdermal, inhaled, and parenteral routes bypass first-pass metabolism
• Never crush ER, EC, sublingual, or buccal forms — crushing ER products causes dose dumping
• Shake suspensions; measure liquids with an oral syringe
• Potassium chloride: never IV push
• Vincristine: IV only — fatal intrathecally
• Fentanyl patches only for opioid-tolerant clients; no heat; effects persist after removal
• IM absorption is poor in shock — use IV
• Epinephrine for anaphylaxis is IM in the mid-outer thigh
• IO route is the emergency alternative when IV access fails
• A route change needs a new order; doses differ by route
• Topical drugs can cause systemic effects (timolol eye drops → bradycardia)