Fill 'Em Up

By Angelo De Palma, Ph.D., Contributing Editor

Because pharmaceutical filling bridges the huge gap between bulk manufacture and distribution, every link in the pharmaceutical supply chain contributes to how a drug is dispensed into a saleable container. Whether a drug is sold in single- or multiple-dose format; whether it's administered to one patient or to several or by the patient himself; whether it's split up at a pharmacy "all determine whether a filling line dispenses microliters or liters, single tablets or lots of 500 capsules.

Speed and cost-cutting, recurring themes in filling, impart the flavor of smart inventorying and just-in-time manufacture. Even pharmacology, pharmacokinetics, and active ingredients' chemical structures influence how drug packages are filled.

Packaging should be designed with filling in mind, but packaging and filling experts are not always on the same wavelength. "You'd be amazed at how many programs we enter at the eleventh hour," says Howard Thau, President of Westwood, N.J.-based Sonic Packaging, "where creative packaging designers have proposed a design that can't be filled, or where packages are so expensive to fill that the labor costs more than the drug."

The desire for better safety, compliance and convenience "often at the cost of higher unit pricing" is propelling unit-dose (single-dose) packaging, particularly prefilled syringes and blisterpacks, both specialties of Sonic's. Unit-dose packages, like metered-dose inhalers and to-deliver droppers, present unique problems for liquid and solid-dose filling, respectively. "On a per-dose basis it's always more expensive to produce unit-dose packages," Thau comments.

With some very high-value medications, however, unit-dose syringes can actually be more cost effective than multi-dose preparations, says Jeff Turns, senior vice president for Vetter, a Yardley, Pa., firm that specializes in aseptically filled, self-administered, prefilled single-use syringes and multiple injection devices.

"The 15% to 20% of injectible solutions that are wasted in each multi-dose vial can be worth hundreds of dollars," Turns explains, "which is significantly more than the cost of five or ten vials." Plus compliance, in the long run, can save on overall healthcare costs by reducing the need for more costly interventions. Turns' numbers are verified by Fred McMillan of West Pharmaceuticals, Lionville, Pa., who says that vials for injectible drugs are typically overfilled "by ten to twenty percent" to compensate for waste.

These innovative packages, which necessitate equally novel filling methods, are driven by convenience and dose accuracy. Prefilled syringes are not just for injectibles, adds Marian Robinson, vice president at Baxa, Englewood, Colo., pointing out that syringes are making inroads into oral medications as well.

Sterile Liquids Rule

Manufacturers of tablets and capsules may argue otherwise, but by far the highest value-added filling operation is sterile liquid fill because of the operation's technical difficulty and dire consequences for failure.

Maintaining a clinical fill operation is expensive and requires specialized skills that are only intermittently used. Large pharmaceutical companies therefore tend to farm out sterile fill for development and clinical runs, if not for all their sterile filling needs.

Sterile liquid fill comes in two flavors: aseptic and terminally sterilized, but complex drug structures and formulations are slowly killing terminal sterilization. "These days, fewer and fewer drugs, and no biotech products, are filled that way," observes Tom Thorpe, president of Afton Scientific, Charlottesville, Va. Another reason for outsourcing, says Thorpe, is that " surprise! " in research-driven companies R&D and manufacturing types don't always get along.

"Complex, expensive, aseptic pharmaceuticals are the most likely to sent out to contractors for filling," says Glenn Restivo, life sciences manager at Rockwell Automation, Philadelphia, Pa. "Research-oriented pharmaceutical companies tend to view manufacturing as a necessary evil, and packaging, especially, as a cost center, so they farm it out."

Sterile filling requires dedication and expertise that are often best delegated to specialty fillers. "Good design, good discipline, practice, and training are the keys," Thorpe says.

Because verifying sterility without destroying product is impossible, fillers rely on good records and simulation of their process using vials or syringes filled with microbial growth media. Still, both systematic and nonsystematic errors creep in. So during training, filling line operators are subjected to all manner of intervention scenarios, for example retrieving a stopper or broken vial from a relatively inaccessible part of the machine, starting and stopping a line, and fixing a machine malfunction. These should be rehearsed and repeated, says Thorpe, until workers' technique is perfected.

As a filler of small-scale commercial products and clinical trial doses, Afton understands its position within this marketplace, according to Thorpe. "It's very difficult for fillers that do very large runs to do small runs. Since cost and operating structures are different for very large and very small runs, it may not be economical for filler or customer." Because one size won't fit all, Afton's customers tend to be smaller biotech companies, universities, government agencies, and larger firms with immediate need for finished, small clinical batches.

A larger contract filler, Thorpe explains, will consider taking on a small job for an established customer with whom they have significant other business. "But if it's for a one-off biotech with no history, large fillers balk because only 19% of Phase I drugs make it."

Aseptic Wrinkles

Exciting new wrinkles to aseptic filling include blow seal (for larger bottles) and form seal (unit- or several-dose) filling. Both extrude polyethylene resin into a mold, fill the cavity aseptically, and punch out finished product.