A Fresh Look at Tubes

Tubes may be among the oldest, best established pharmaceutical packages, but they still face challenges.

by Jim Wagner, Editor at Large

Tubes are among the most reliable pharmaceutical packages available, which is why more than 3 billion were filled last year, according to the Tube Council of North America (New York City). But just because the tube has a long history doesn't mean it's immune to the changes taking place in the industry. The issues at hand: developing a reliable child-resistant (CR) closure, improving filling systems, and creating innovative graphics.

CHILD-RESISTANT CLOSURES

Until recently, the holy grail for tubes was a closure that was functional yet child resistant and senior friendly. At first, the engineering challenges seemed insurmountable. Unlike a rigid package, a tube flexes when force is applied to a closure, making the standard continuous-threaded (push-and-turn) closure impractical. Manufacturers and closure suppliers continued studying the problem, but development work moved slowly. Ultimately, the Consumer Product Safety Commission (CPSC) had to provide the impetus for another run at a CR tube closure.

The push came from CPSC's final rules requiring CR closures for products containing gels, creams, or ointments with 5.0 mg or more of lidocaine or 0.5 mg of dibucaine in a single retail package. Rather than change packaging—a time-consuming prospect that could detract from brand equity—engineers returned to their CAD systems for a fresh look at CR tube closures.

Photo courtesy of Schering-Plough HealthCare Products/Roni Ramos
 

The first over-the-counter product with a child-resistant, senior-friendly closure will appear this spring. It will be launched by Schering-Plough HealthCare Products (Memphis) for Dr. Scholl's Cracked Heel Relief Cream. The product contains lidocaine as an active ingredient.

Michael Tune, senior research packaging specialist, package development, Schering-Plough, says the key to designing the package was to find a way in which the closure could be opened without relying on a rigid primary container. "The squeezability characteristic that makes the tube such an efficient package becomes a liability in child-resistant design," says Tune. "A traditional push-and-turn closure would require downward pressure on the flexible package. The accumulation of product that would occur on the thread finish could also compromise the long-term child-resistance of the package. Our job was to design the package so that one could open it without a firm grip on the tube."

The closure that solved the problem was from Polytop (Slatersville, RI). A custom tube finish was developed in collaboration with Courtaulds Packaging/Thatcher Tube (Woodstock, IL). The closure has a flip-spout dispenser molded into the center. It opens by pushing down on the edge of the dispenser. Most children have a difficult time holding the tube while applying sufficient force to swing up the dispenser.

The closure was tested by Perritt Laboratories (Hightstown, NJ) under the new CPSC guidelines for child safety and senior friendliness. It passed handily, according to Tune. "The tests confirmed that children do not have the dexterity or strength to open the closure," he explains. The project took six months from design to finish. The HDPE tube is fitted with a 24-410 continuous-threaded finish with a nonremovable ratchet feature that locks the closure in place.


 

CPSC Requirements for Lidocaine and Dibucaine

Approximately 12.1 million units of lidocaine-containing products were sold to consumer outlets in 1992, according to the Consumer Product Safety Commission (CPSC). More than half (6.2 million) of those products were cream and ointment formulations available in tubes. In addition, the commission's staff estimates that fewer than 400,000 bottles of consumer-ready prescription viscous lidocaine were sold. Dibucaine, used for temporary relief of painful sunburn, minor burns, scrapes, scratches, nonpoisonous insect bites, and external hemorrhoidal pain, is sold in OTC preparations in 30-g and 1-, 1.5-, and 2-oz tubes. It is estimated that approximately 900,000 tubes of dibucaine-containing preparations were sold to consumer outlets in 1992.

According to the Federal Register, CPSC expects marketers to develop CR multidose tubes compatible with specific lidocaine or dibucaine formulations. The commission concludes that the development of CR packaging for these tubes is technically feasible, practicable, and appropriate based on existing technology. Development can cost from $145,000 to $585,000 and can take up to 36 months. Additional time would be needed for stability testing of the preparation in the new package. Increased costs of up to $4.40 per tube are estimated if development is done on an individual company basis.


 

The lidocaine/dibucaine regulations have other closure manufacturers working on suitable designs for tubes. Pressta Ltd. (Kesswil, Switzerland), represented in the United States by Europack Ltd. (Medfield, MA), claims to be the first firm to offer a patented child-resistant closure with tamper-evidence features. The flexible one-piece Pressta closure has two pressure points on opposite sides. Squeezing the points allows the cap to be turned and twisted over the shoulder ramp. The shoulder of the tube was redesigned to support the twist force without affecting the shape of the tube.

The Cebal Division of American National Can (Norwalk, CT), part of the Pechiney Group, developed the S16 Tote closure with a tamper-evident feature. The orifice seal, molded during the manufacture of the tube, extends above the orifice. A molded threaded cap covers the seal. If the extended seal is missing, consumers can instantly see that the tube has been opened. To open the tube, the user unscrews the cap, inverts it, fits it over the orifice seal, and twists. The seal breaks off and remains in the cap.

FILLING AND SEALING

One of the chief benefits of tubes is that they are relatively easy to fill. According to the Tube Council of North America, filling involves a nozzle that dives into the tube before the filling process begins. As the product is discharged, the nozzle is retracted out of the tube, keeping a constant distance between the nozzle outlet and the rising level in the tube. After filling, the product, which often strings, is cut off with one of several techniques.

The most critical step is the seal between the piston of the volumetric dosing system and the cylinder. Some OTC products, such as toothpaste, are abrasive. Typical seals made from polyurethane, Viton, PTFE, or polyethylene are subject to wear and have to be replaced at regular intervals.

Another critical part of a tube filler is the sealing method. Metal tubes are closed by folding, typically a double fold, four fold, or saddle fold. Laminate tubes are sealed with heated jaws. Laminates with aluminum foil can be safely sealed with high-frequency sealing methods, which send an eddy current into the foil layer, heating up the foil and the surrounding layers of plastic.

The preferred sealing method is hot air. The seal area inside the tube is heated, and then a subsequent station presses the tube bottom together and cools the seal area. The technique produces a tight seal with good esthetics and alphanumeric characteristics for date and lot coding.

GRAPHICS

Tube decoration has always leaned toward a medicinal look for obvious reasons. In the 1990s, however, relentless competition and expiring patents have tubes fighting for shelf space. The result has been an upgrade in how tubes are decorated. The once plain white tubes have been replaced by those with color graphics, vignettes, graduations, bold colors, and nontraditional shapes and sizes.

The revolution is due to advances in printing technology. Tube manufacturers routinely offer high-quality printing using the latest in combination printing and other technologies for tubes that look silk-screened, but at a fraction of the cost. Montebello Packaging (Oak Park, IL) for instance, has its M-Deco print transfer that creates quality images on runs as small as 100 tubes. Prior to filling, the M-Deco process transfers images as needed, according to the company.

Placing more emphasis on graphics does put more responsibility on tube engineers and designers. Larry Sprinkles, Dixie Graphics (Nashville, TN), says manufacturers, prepress houses, and the tube printer must all work more closely to ensure the quality of the graphics.

The next generation of tubes is already appearing on shelves. Graphics are sharper thanks to digital prepress technology. The quality of four-color graphics mirrors that of photographic quality. Even spot graphics are more precise, again thanks to digital software. All told, graphics are better than ever.

The same is true for tubes since the number of options available has increased from year to year. Tube manufacturers are consolidating, but the level of innovation continues to rise. Tubes will certainly be a key pharmaceutical package for years to come.

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