Sophisticated gas detectors are helping a pharmaceutical manufacturer measure coating thicknesses on drug tablets. The sensitive detectors—from Minneapolis-based Sensor Electronics—continually sniff ethanol gas in the exhaust streaming from the coating machine. The gas detectors also provide protection for plant personnel, says technical engineer John Levasseaur at Paddock Laboratories in Minneapolis.
But how the company uses the gas detectors to monitor tablet coating thickness is particularly intriguing. Tablets are fed into a twirling tumbler where a small-bore feeder sprays a bonding mist of the ethanol carrier plus a color tint, a lubricant (for easier swallowing), on the drug itself.
Depending on the coating, tablets are tumbled from 30 minutes to four hours, with the ethanol feed, temperature and humidity all closely controlled. In effect, measuring the ethanol concentration in the exhaust measures the coating thickness on the tablets, initially set by a flow meter upstream. For example, a too-high ethanol level means a too-thick coating, so the spray mist ratio is decreased. The ethanol proportion in the exhaust then verifies the feeder setting.
The gas detectors do double duty. Ethanol is explosive, so if ethanol levels in the exhaust duct reach a preset LEL (lower explosion limit) the detector triggers alarms to warn workers; if the ethanol concentration continues to go up, the gas-detection system turns on fans to flood the area with outside air.
Other detectors monitor ethanol levels in the spray pump console and the room itself.
Paddock Laboratories was founded some 30 years ago by a Duluth druggist tired of mixing standard formulas in small quantities for his customers. Figuring other pharmacists probably felt the same way, Paddock set up a laboratory to make common drug compounds at a low cost. From that small start Paddock has mushroomed to some $200 million annual sales to drugstores, distributors, chain stores, big-box retailers, and mass marketers in the U.S. and Canada.
The company concentrates on niche markets for generic drugs. “For example,” says Levasseaur, “we won’t copy large-selling drugs. When the patent on them expires, every generic drug manufacturer in the world will be coming out with a replacement. Competition will go up, volume will go up, prices will go down, profits will go down.
“We don’t want to get into battles like that. Instead we look for proprietary drugs with patents about to expire – drugs with a low volume but a good potential profit profile. If we can duplicate that drug at an advantageous cost we will go in.”
“Timing is critical. You want to be first with an FDA-approved generic, because with that approval comes a 30-month exclusive. That gives us—or any drug manufacturer— 30 months to cement our reliability and our relationship with our customers.”
“But with any generic—or any drug, for that matter —reliability is the key. Closely monitoring ethanol levels in our coating process helps us maintain that reliability.”
Tom Probst is Public Relations Manager for Sensor Electronics Corporation