Four didn't do anything for you? What were you eating during your cleansing period? Do you suffer from constipation or any digestive disorders?
Whenever I do the Oxypowder cleanse, which is about three times a year. I will start with four capsules, and then slowly work my way up to 6. For me, 6 capsules is more than effective! I usually don't need more than four, but I increase it to six for maximum cleansing. But I would imagine that if you suffer from constipation or have alot of impacted fecal matter inside your colon, that four might not be enough.
I'm certainly no expert, but I would recommend you try slowly adding one or two capsules until you reach what works for you. If that doesn't work, then take a look at your diet during your cleansing period. If you eat alot of junkfood, fastfood, or alcohol, it can skew the effectivness of any colon cleansing product.
Call the oxypowder people and seek their advice...