The decision to cosign with someone on their credit card account should be taken after much thought and consideration. Usually a credit card company requires a person to cosign when the person applying for the credit does not have a good enough credit history and financial credentials to qualify for the credit card individually. If you cosigned on a credit card account with someone than you took on the guarantee of paying off the debt of the principal owner of the credit card in case he were to default on the debt.
For this reason even if you want to remove yourself from a credit card account after cosigning on it you might not be able to do so. Since the credit card company considered the primary applicant as a bad risk requiring you to sign as a joint account for the full security they will not allow the credit card accounts to function without you providing the Guaranty on the debt amount.
The only recourse that might be open to you in this case is to request the primary applicant for whom you cosigned on the credit card account to pay off the balance on the credit card and request the credit card company to close the account. He or she should then apply for a new credit card account on an individual basis solely on the strength of their credit history and credit score.