Post-exposure prophylaxis (PEP) is a treatment that can help prevent the transmission of human immunodeficiency virus (HIV) after potential exposure. PEP involves taking a combination of antiretroviral (ARV) medications within 72 hours of exposure to HIV. Common side effects of PEP include: Nausea: Many of the medications used in PEP can cause nausea, especially when first starting treatment. Fatigue: Fatigue is a common side effect of PEP, and can be especially noticeable in the first few weeks of treatment. Diarrhea: Some of the medications used in PEP can cause diarrhea, which can be mild to severe. Headache: Headaches are a common side effect of PEP, but usually go away after a few days. Skin rash: Some of the medications used in PEP can cause a skin rash, which can be mild or severe. Depression and anxiety: PEP can affect mood, and some people may experience depression or anxiety while taking PEP. Insomnia: Some of the medications used in PEP can cause insomnia, or difficulty sleeping. Liver problems: Some of the medications used in PEP can cause liver problems, including an increase in liver enzymes. Peripheral neuropathy: Peripheral neuropathy is a condition that can cause tingling, burning, and numbness in the hands and feet. Lactic acidosis: This is a serious condition that can occur as a result of taking certain ARV medications. It is characterized by an increase in lactic acid levels in the blood and can lead to symptoms such as fatigue, abdominal pain, and difficulty breathing. It's important to note that not everyone will experience these side effects, and some people may not experience any side effects at all. If you experience any side effects while taking PEP, it's important to talk to your healthcare provider as soon as possible. They can recommend ways to manage side effects, or switch you to a different medication if necessary.