Excreted: How medications leave your body — fast facts you can use

Ever wonder what happens to a pill after you swallow it? "Excreted" just means the body gets rid of a drug or its breakdown products. Where and how that happens changes how the drug works, what side effects you might see, and whether your doctor needs to change the dose.

Main routes of excretion

Most drugs leave the body one of three ways: through the kidneys (urine), through the liver and bile (then stool), or via the lungs, sweat, or breast milk. Kidney excretion matters for drugs like ACE inhibitors (for example, enalapril) and many antibiotics. Liver/bile removal is key for statins like simvastatin and for drugs that get heavy liver processing, such as sildenafil. Some drugs split their exit between urine and feces — clopidogrel metabolites and certain antibiotics do this.

Topical medicines usually give less systemic exposure, but a steroid cream or topical triamcinolone can still be absorbed and then excreted by the kidneys as metabolites. Minoxidil topical largely stays local, so systemic excretion is minimal unless you use large amounts.

Why excretion changes treatment

Kidney or liver trouble slows drug clearance. That means the drug can build up and cause extra side effects. Simple example: if your kidneys don’t clear a medicine well, you may need a lower dose or a longer gap between doses. Same with liver disease for drugs cleared by the liver. Older adults often clear drugs slower, too.

Drug interactions can change excretion. Some medicines block liver enzymes or alter kidney function and make another drug stick around longer. That’s why doctors warn about mixing certain antibiotics, heart drugs, or over-the-counter painkillers with prescription meds.

Practical signs a drug might be building up include more intense side effects, new dizziness, or unusual tiredness. If you start seeing that after a changed dose or a new medicine, check with your pharmacist or doctor.

Labs help. Creatinine, eGFR and liver enzymes are the common tests clinicians use to decide whether to adjust doses. For example, ACE inhibitors and many blood pressure meds need attention if kidney tests are off. Antibiotics like moxifloxacin and painkillers like naproxen also deserve caution with reduced kidney or liver function.

Quick tips: tell your provider about all medicines and supplements you take; ask if dose changes are needed when kidney or liver tests change; avoid unnecessary over-the-counter NSAIDs if you’re on certain blood pressure or heart meds; and ask whether a topical medicine might still affect your system.

Want real-world examples and deeper reads? Check the tagged articles below on drugs like Vasotec (enalapril), Zocor (simvastatin), Plavix, Decadron, and more to see how excretion affects dosing, safety, and everyday use.