As the generic version of Lipitor goes on sale this week, patients taking the top-seller lowering cholesterol drug may be considering the risks of switching to the cheaper option.

Generic drugs are as effective as the original, according to a Consumer Reports Magazine report. They may have different color, shape, size or taste but by law, all must have the same active ingredients as the brands they copy.

Generics can also save money in co-payments as well as out of the pocket purchases.

If patients pay a flat fee-co-pay for the drugs, the co-pay is lower. For example, a person may pay $5 to $15 for the generic drug but $15 to $35 for the brand-name drug, according to Consumer Reports.

If the co-payments are based on the full cost of the drug, there are also savings. The full cost of a brand-name drug is about 3 times the cost of the generic one. For instance a 30 percent co-pay plan could lower the price of a generic drug to $15 when the brand-name costs $45.

For uninsured patients the savings could be more significant. For example, a brand-name drug that costs $150 could cost $50 on its generic version in out of the pocket purchases.

However, for those patients who prefer to stay on the original drug, Pfizer has worked out discounts for them as it makes effort to keep the market of the drug strong. (Lipitor brings in nearly $11 billion a year to Pfizer, about a sixth of the company's revenue).

For example, Pfizer is offering a discount card to get Lipitor for a co-payment of $4 a month for insured patients though some restrictions apply, according to Pfizer's website.

Pfizer also negotiated lower prices for Lipitor with several large insurance companies and pharmacy benefit managers so that the cost for Lipitor are down to the price of a generic or slightly less, according to a report from the Associated Press.

For more information about the $4 co-payment for Lipitor click here.