Routes of drug administration
Topic Notes
Common Routes of Drug Administration (Short‑Reference Guide)
| Category | Route | Typical Uses / Notes | Example Drugs |
|---|---|---|---|
| Systemic (enter one‑way or multiple) | Oral (PO) | Most convenient; affected by first‑pass metabolism and gastric pH. | Acetaminophen, Metformin |
| Intravenous (IV) | Immediate, 100 % bioavailability; used for acute or unreliable gut absorption. | Amoxicillin IV, Lidocaine | |
| Intramuscular (IM) | Rapid absorption; used when IV access is impractical. | Diazepam IM, Sotalol | |
| Subcutaneous (SC) | Slower absorption than IM; convenient for insulin, heparin. | Insulin, SCIG | |
| Inhalation (nebulized, dry‑powder) | Direct pulmonary delivery; systemic or local lung action. | Albuterol, Fluticasone | |
| Intra‑arterial | Rarely used; mainly for regional cancers or ischemic disease. | Selective chemo‑embolization | |
| Intradermal | Limited to vaccines or allergy testing; low systemic absorption. | BCG vaccine | |
| Intrathecal / Intracerebral | Direct CNS delivery; bypasses BBB. | Morphine IT, Bromocriptine CT | |
| Intraperitoneal | Used in oncology or animal studies; moderate systemic absorption. | Paclitaxel IP | |
| Intravenous‑in‑traveler (IVT) / catheter‑based | Catheter‑directed drug delivery (e.g., DES). | Drug‑eluting stents | |
| Local (targeted) | Topical (skin) | Surface or intradermal skin exposures. | Hydrocortisone cream, Benzocaine |
| Transdermal | Patch‑based prolonged release into circulation. | Nicotine patch, Fentanyl patch | |
| Ophthalmic | Eye drops, gels. | Timolol eye drops, Loteprednol | |
| Otic | Ear drops or irrigation. | Metrizamide, Diclofenac otic | |
| Vaginal | Local or systemic absorption. | Clotrimazole vaginal cream, Estradiol | |
| Rectal (suppository or enema) | Alternative when oral is contraindicated. | Loperamide, Alanyl‑glutamine | |
| Sublingual / Buccal | Rapid absorption through oral mucosa, bypassing first‑pass. | Nitroglycerin SL, Clonazepam | |
| Nasal (spray or insufflation) | Quick onset; mucous membrane absorption. | Fluticasone nasal spray, Alcohol | |
| Intranasal aerosol | Same as nasal, often for medications requiring larger surface area. | Ketamine (clinical trials) | |
| Intra‑vaginal | Local delivery; e.g., lactobacillus for bacterial vaginosis. | Lactobacillus rhamnosus | |
| Other all‑in‑one (e.g., transbuccal liquid, intramuscular injection) | Specialty uses. | Fragmented/LS-1 (breast cancer implant) |
> Key Points
> • First‑pass metabolism: oral → hepatic → plasma (≈ 75–90 % lost for certain drugs).
> • Bioavailability: IV = 100 %; others vary (IM 90–100 %, SC 50–80 %, topical 1–10 %).
> • Onset: Inhalation and intranasal ~ minutes; oral 15–60 min; IV • Convenience vs insertion risk: Oral > topicals > IM > SC > IV.
References*
1. Goodman & Gilman’s The Pharmacologic Basis of Therapeutics, 14th ed. (Elsevier)
2. Katzung & Trevor’s Pharmacology Examination & Board Review, 11th ed. (McGraw‑Hill)
3. Rang & Dale Pharmacology, 8th ed. (Pearson)
Use this table as a quick cheat‑sheet for exam prep, clinical notes, or teaching moments.
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