There are many different schools of thought on malaria prevention, but this is a general idea of the malaria prevention options that most travel doctors prescribed to their patients.
250 mg. Take one tablet a day with a meal at the same time of the day. You should start this 1 day before, take it each day, and then for one week if you had exposure to malaria.
250 mg. Take one tablet a week starting 1 week before possible exposure, every week during, and for four weeks after possible exposure to malaria mosquitoes.
100 mg. Take one tablet daily starting 2 days prior, during and four one month after possible exposure to malaria.