Tag: First pass metabolism

The medical abbreviation PO is derived from the Latin phrase *per os*, which means 'by mouth'. So, **what does PO mean on a prescription**? It's a crucial instruction indicating that a medication must be taken orally, a standard direction for countless drugs, from pain relievers to antibiotics.

By bypassing the digestive system entirely, a **therapeutic parenteral drug** often achieves a much more rapid and predictable effect than oral medications. This method of drug delivery, which includes injections and infusions, is essential for patients who cannot swallow or require immediate, high bioavailability medication.

Oxytocin, the hormone best known for its roles in childbirth and social bonding, is a peptide that is almost entirely destroyed by the body's digestive system. This critical fact explains why standard oral administration, such as swallowing a pill, is an ineffective method for delivering this medication.

According to the National Institutes of Health, absorption is the first stage of pharmacokinetics, describing the movement of a drug from its administration site into the body's circulation. Understanding **what are the steps of drug absorption** is critical for explaining how medication reaches its target and produces a therapeutic effect.

Intravenous administration is defined as having 100% bioavailability because the drug is delivered directly into the bloodstream. This makes it the standard against which all other routes are measured when understanding **Which form of drug has the highest bioavailability?** and overall drug effectiveness.

It takes approximately 30-60 seconds for an IV medication to enter systemic circulation and take effect, compared to the 30-90 minutes often required for an oral dose. This dramatic difference in speed explains why is IV faster than oral, and it's a fundamental principle of pharmacology rooted in how the body processes drugs.

By definition, intravenous (IV) administration provides 100% bioavailability, meaning the entire drug dose reaches the bloodstream to act [1.4.2, 1.3.5]. This direct entry is the fundamental reason **why is IV so fast** compared to other methods like oral pills.

The global transdermal skin patches market was valued at USD 7.82 billion in 2023 and is a key method for drug delivery [1.6.1]. The fundamental question for many is: **do transdermal medications have a systemic effect?** The answer is yes; they are specifically designed for this purpose [1.2.1, 1.2.5].

In 2024, topical administration routes dominated the dermatological drugs market, accounting for a 60% revenue share [1.13.1]. This highlights a key choice in medicine: understanding **what is the difference between systemic and topical medicine** and when each is appropriate.

For patients who cannot take oral medications due to nausea, vomiting, or swallowing difficulties, rectal administration can be a viable alternative for certain drugs under medical supervision. However, you cannot simply give tablets rectally; they are not formulated for this delivery route and can be ineffective or even dangerous.