# Ethanol Metabolism

**Alcohol** or **Ethanol Metabolism** occurs in the **liver** through several steps, beginning with ethanol (alcohol), proceeding through acetaldehyde, and ending with acetate (acetic acid), which is excreted in the urine.

First, ethanol can be metabolized into **acetaldehyde** in 3 ways. The most important way is through **alcohol dehydrogenase** in the **cytoplasm**, which is blocked by the drug, **fomepizole**. Alcohol dehydrogenase operates via **zero-order kinetics**, which means that it operates at a constant rate regardless of how much alcohol is present (amount ingested). Less important enzymes include **CYP2E1** in the **microsome**, or **catalase** in the **peroxisome**.

The acetaldehyde is then metabolized into **acetate** through the actions of **aldehyde dehydrogenase**. The drug **disulfiram** is given to discourage drinking, as it blocks aldehyde dehydrogenase and leads to the build-up of the toxic intermediate: acetaldehyde.

The metabolism of alcohol usually generates 2 molecules of NADH from NAD+, which **increases the NADH to NAD+ ratio**. The increase in this ratio leads to a number clinical findings, such as **lactic acidosis**, **fasting hypoglycemia**, **hepatosteatosis**, and **ketogenesis**.

Find Ethanol Metabolism and more [Biochemical Pathways](/content/browse#playlist-4028/index.html) among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.