Which category of medications is used to prevent asthma attacks and is typically taken twice per day?

Long-acting beta agonists (LABAs) are primarily used for the maintenance treatment of asthma and are designed to prevent asthma attacks. They are effective in providing extended bronchodilation, which helps to open the airways and maintain better airflow for an extended period, typically lasting anywhere from 12 to 24 hours. LABAs are often prescribed to be taken twice daily to offer sustained control of asthma symptoms, particularly for individuals who experience nocturnal symptoms or frequent daytime symptoms.

In contrast, short-acting beta agonists are utilized as "rescue" medications to provide quick relief from acute asthma symptoms but are not meant for long-term management and are not taken regularly. Inhalable corticosteroids are important for reducing inflammation in the airways over time but are usually administered frequently throughout the day rather than in a fixed twice-daily regimen. Leukotriene modifiers are oral medications that also contribute to asthma management by reducing inflammation but typically are not classified in terms of usage frequency like LABAs. Thus, LABAs specifically fit the criteria outlined in the question regarding their preventive role in asthma attacks and dosing schedule.