A recent Forbes report showed that the top six most expensive medications in the world (which cost anywhere from $200,000 to $400,000 a year for a typical treatment) were all so-called "orphan drugs" - meaning, medications used to treat very rare conditions.

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"Smaller patient populations mean higher prices," says Becky Foster of Foster Healthcare, a consulting firm serving biotech and pharmaceutical companies. "Very small populations - conditions that have 'orphan' or 'ultra-orphan' status - make it difficult to recoup the costs of development or provide a steady revenue stream that would allow them to invest in an ongoing development program once the drug is on the market."

However, many common diseases and conditions can also be expensive to treat. The actual out-of-pocket costs to patients can vary widely, though, depending on their insurance coverage and their eligibility for any government assistance programs or manufacturer-sponsored resources. Here are six very common conditions for which the treatments can be extremely costly.

  1. CancerThis is probably the most obvious one. According to the Medco 2010 Drug Trend Report, in the past four years, almost all of the drugs approved for cancer treatment have cost more than $20,000 for a 12-week course.
    However, costs for some cancer treatments may have actually decreased recently. According to the Medco Report, several cancer drugs became available in generic form for the first time in 2009, giving patients a cheaper option.
  2. Multiple SclerosisThe Medco Report says MS treatment spending increased 24.7% (per patient per month) from 2008 to 2009. According to HealthCentral, the most common treatments for MS can cost around $2,000 per month or more - and patients often must take them for their entire lives. (Learn more about cutting your healthcare costs, read Cut Your Cost for Marketplace Health Insurance.)
  3. DiabetesAccording to a Consumer Reports survey, diabetes drugs can costs up to $250 per month each, and many patients will need to take more than one drug at a time. In fact, a ConsumerAffairs.com report on diabetes drugs said that diabetes patients take an average of 8.9 prescription drugs on a daily basis. Insulin pumps can cost more than $5,000 plus another several hundred per month for pump treatments - but most insurance plans cover much of that cost.
  4. Rheumatoid ArthritisA variety of different types of drugs have been used to treat rheumatoid arthritis. In recent years, a group of drugs known as TNF inhibitors have become more common as part of a RA treatment regimen. These drugs, which must be given via injection, can cost at least $16,000 per year, according to MedScape.
  5. High Blood PressureThere are numerous drugs commonly prescribed for patients with high blood pressure, and - as with diabetes - patients often require a regimen that involves daily doses of several different medications. Data compiled by Consumer Reports shows that name brand blood pressure drugs can cost more than $400 per month each. However, all of the major blood pressure drugs have equivalent generic forms that cost much less. (Learn about the alternatives to normal healthcare in Concierge Healthcare: The Pros and Cons of Having a Doctor On Call.)
  6. DepressionThere are many antidepressants on the market today, and patients often must try several before they find one that works best for them. These drugs can have an average monthly cost of up to $870 each, according to Consumer Reports. Insurance companies can vary widely as far as what percentage of the cost they will cover for these and other drugs used to treat psychiatric conditions.

The Bottom LineWhile the most expensive drugs may be connected to rare diseases, there are lots of common conditions that require some pricey prescriptions, as well. However, you can often save considerable money by opting for generic versions or switching to a lower-deductible insurance plan. (For related reading, take a look at How U.S. Healthcare Costs Compare to Other Countries.)

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