Fenbid is a sustained-release tablet of ibuprofen, which acts slower but lasts longer. It usually takes more than an hour to take effect. It can last for about 10 hours, but if you eat it, you will develop drug resistance. I have been taking it for a year and usually take 4 pills a month. Now it takes two to three hours to take effect and can only work for six or seven hours. You can take different painkillers, and their mechanisms of action are different.