As an antihypertensive drug, losartan can effectively lower blood pressure and is generally safe. Adverse reactions mainly include the following: first, the effect on the neuropsychiatric system, which can be manifested as headache, dizziness, and insomnia in some patients. Such adverse reactions are mild and transient, and generally do not require termination of treatment. Second, hypotension, mostly seen in taking too large a dose of drugs or patients are more sensitive to antihypertensive drugs. Third, allergic reactions, including dermatitis, rash and allergic edema. Fourth, gastrointestinal adverse reactions, including nausea, vomiting, abnormal liver function, etc. Fifth, hyperkalemia, cloxacin potassium has the side effect of elevated blood potassium, especially in patients with renal insufficiency, attention should be paid to monitoring blood potassium. Sixth, the blood system, long-term use of patients may have anemia or thrombocytopenia.