Sentinel Spectrum must be administered monthly, preferably on the same date each month. If given seasonally, the first dose must be given within 30 days of the dog's first exposure to mosquitoes. The last dose must be given within 30 days after the dog's last exposure to mosquitoes. Treatment with fewer than 6 monthly doses after the last exposure to mosquitoes may not provide complete heartworm protection. To ensure complete absorption, always give Sentinel Spectrum chewables to dogs either with or immediately after a normal meal. Food is essential for proper absorption of the product into the bloodstream.