Have you ever tried to get your prescription filled at the local pharmacy, only to be told that your employer's benefit plan doesn't cover the drug your doctor prescribed? Or perhaps you learned the price for a prescription you fill each month suddenly jumped from $15 to $30?

It's no good blaming the pharmacist. She doesn't set the price you pay for the little purple, yellow, and blue pills. Yet, day in and day out, she has to break the bad news about rising prescription drug costs to unhappy customers. To avoid shock at the Rx counter, you have to learn the minute details about how your prescription drug benefit works.

Plans vary greatly from company to company,from health plan to health plan, and from year to year. "Benefit structures are very complicated sometimes," says Diana Helfinstine, vice president of customer care operations for AdvancePCS, a large prescription drug benefits administrator based in Irving, Texas. 

Be sure to read carefully each communication from your benefits department, insurer, and prescription drug card company. You may even wish to start a file of these communications, so you'll have the information handy when you need it. Here's some background you might find useful. 

The "nuts and bolts" of Rx plans

Most employment-based prescription drug benefits are administered by companies known as "pharmacy benefit managers," or PBMs, such as AdvancePCS, Medco Health Solutions, and Express Scripts. Employers and insurance companies contract with PBMs to help design Rx benefit plans, process pharmacy claims, and look for red flags in drug usage. PBMs negotiate with pharmaceutical manufacturers for volume discounts on prescription drugs.

They employ medical professionals to recommend drug coverage and courses of therapy. PBMs help employers decide which drugs will be covered, at what price levels, under the plan. What emerges is a list of covered prescription drugs, both generic and brand name, called a "formulary."

As Helfinstine puts it: "A formulary is a list of medications that have been determined to be clinically appropriate, and they're the most cost-effective for the drug therapy that's required." The most restrictive formularies are "closed," meaning, if the prescription drug is not on the list, it's not covered under the plan. Consumers who wish to purchase that drug have to pay full price for it.

The most generous formularies, in contrast, are "open." Plan members may receive reimbursement for prescription drugs not listed on the formulary (although there may be exclusions). 

Whether closed or open, formularies usually give consumers a price break for selecting generic drugs. Generics contain the same active ingredients as the brand names and have the same medical benefits. Not all brand name drugs have a generic equivalent, due to patent protections.

But as more generics become available each year, they're gaining popularity with consumers. "Generics are a therapeutic equivalent to the brand, and for all practical purposes they are nearly identical to the brand," says Scott Bond, vice president of account services for AdvancePCS. Tiered formulary plans try to drive generic use by providing an impressive cost incentive to consumers.

These formularies typically divide prescription drugs into three tiers: generics, "preferred" brands, and "non-preferred" brands. Progressively higher "copayments" are assigned to each tier. Generics may require a $10 copay, for example, while preferred brands cost $25 and non-preferred brands cost $50. Plans with a "coinsurance" approach, on the other hand, require consumers to pay a percentage (perhaps 50%) of the cost of each prescription drug, regardless of whether it's a generic or a brand name.

Plan designs vary widely: Some combine both a copay and a coinsurance approach. Some require consumers to meet a deductible before benefits kick in. PBMs often establish business relationships with certain pharmacies, which are deemed "in-network" pharmacies. You may be required to fill your prescription at one of these pharmacies, or you may receive lesser benefits if you have your prescription filled outside the network. 

Some prescription drugs require "prior authorization" from your physician before your plan will allow them to be filled at your pharmacy. This means the drug is not favored as the first line of treatment for your condition. It's probably more expensive than the preferred drug but not necessarily more effective. Your doctor may have to defend the choice before it will be covered. 

Save your Rx dollars

To take a bite out of rising drug costs, get to know the incentives your prescription drug plan offers and how to take advantage of them. "We recommend that consumers take their formulary list to their physician and ask questions about prescriptions the physician may recommend," notes Helfinstine. Many PBMs, including AdvancePCS, provide an abbreviated formulary list of the most commonly prescribed drugs for this very purpose. 

Ask your doctor whether a generic substitute is available for the prescriptions you're taking. Ask about alternative courses of therapy that may be equally effective but cost less under your plan. Update your doctor on the prescriptions you're currently taking and ask whether you still need them all. 

One of the best ways to save money in your prescription drug plan is to take advantage of mail-order discounts that may be available for "maintenance" medications you need to take on an ongoing basis to keep chronic conditions such as diabetes or hypertension under control. In many plans, you can receive a 90-day supply of medications through the mail for the same cost as a 30-day supply at your local pharmacy.

Of course, there are some drawbacks to mail order. It's a hassle to fill out forms and mail in your prescription. Then you'll wait several days for your prescription to arrive. Some drugs may not be available through the mail order program. But it's worth finding out if they are.

You could save hundreds of dollars a year if you're willing to accept the extra paperwork and the wait time. Keep an eye on mid-year formulary changes. If a generic drug is introduced for the brand name medication you're currently taking, for example, it may suddenly appear in the lowest co-payment tier.

Meanwhile, your prescription might move from the preferred to non-preferred tier. When it comes time to shop for a health plan again during open enrollment season, find out what would happen to your current prescription drug regimen under each plan you're considering.

Even if you intend to stay with your current plan, find out about changes to the formulary and payment structures. If you want to switch health carriers, find out who the PBM is and what its policies are under the plan. If it's the same PBM you've experienced with your current carrier, that doesn't mean the rules will be the same. 

"The fact that a PBM has a different contract with the other major medical carrier may completely change the terms of the contract," cautions Douglas Hay, vice president of professional affairs for the National Community Pharmacists Association. "The impact may be on the day's supply consumers are allowed. It may force them into mail order pharmacy. It may require that they switch medications.

It may require that they pay a different copay." Call your PBM's 800 number if you're unsure what the new plan covers. Many PBMs have pharmacists and customer service representatives available around the clock to answer your questions. Information may also be available on the business's web site.