I am not sure exactly where pentasa dissolve. For the best answer, you can call your pharmacist or IBD nurse.
Some CD patients with mild disease keep well on mesalamine (molecule found in Pentasa) for years, I have read several testimonies here on the forum. If your disease is mild, you have a chance, remain positive

Give it some time, at least a couple of weeks and if symptoms persist, call your GI. If symptoms increase, call right away.
Still i would call the Dr or nurse to know when to start the 3 x a day regimen. Its best to create a relationship with your medical team so that they know what is going on for you. Wishing you well.