Tablet Manufacturing – Tablet Press / Coating Basics
By Neal Collier on Nov 04, 2010
When we last left the Tablet manufacturing process (see Pharmaceutical Manufacturing - Tablet Granulation Basics – 9/1/2010) we were ready to take our granulate and turn it into tablets. I know you have all been waiting for the exciting conclusion of the process, but before we do, here is a quick recap: stuff is mixed and blended; other stuff is added and also mixed; the whole mess is granulated, after which more stuff is added and then the tablet batch is ready for the tablet press.1
OK, let’s get finished!
The batch of active ingredients is now ready to add to the Tablet Press. Yet what, you ask, is a Tablet Press? A Tablet Press (sometimes called a Tableting Machine, or “that dratted contraption”) is a computer-controlled industrial-grade monstrosity capable of pressing hundreds of thousands of tablets an hour.
Today’s high speed tablet presses are very versatile pieces of equipment which possess a dizzying array of cams, rollers, tracks and punches that are easily cleaned and quickly reconfigured by Ray on the 2nd shift. They can be configured to account for changes in batch consistency, required tablet size, or even the tiny numbers or logo on the side. Tablet weight, thickness and density can also be controlled, allowing many different types of tablets to be manufactured.
The batch is placed in one half of a tablet mold (or ‘die’) and the other half of the mold is pressed on top. Pressure is applied and – presto! – a tablet is born!
Oh, just because we made some tablets you think we’re done? We are not done, because our tablets must now be coated.
Coatings make our tablets strong, so that they can handle the rough and tumble world of packaging and handling. Coatings also help increase the shelf-life of the tablet by keeping the active ingredients and other stuff from being affected by oxidation or moisture. Also, since some tablets in their raw form taste like something scraped out of the cat litter box, the coating helps the tablet get past those pesky taste buds. Finally, for those really large tablets, the coating helps keep the Tablet Swallow Ease Factor very high.
The Tablet Coater
Picture a huge industrial-sized clothes dryer with a spray nozzle in the center, and you (more or less) have a Tablet Coater. The Tablet Coater, after being filled with a batch of newly-minted tablets, spins the tablets as the nozzle sprays the tablets with the coating. Then forced air, adjusted to a specific temperature and humidity, is blown across the spinning tablets to dry the coating. This process is repeated for each coating. With the right coating, even yesterday’s donuts can taste great again!
***BLOG ADVISORY*** The following section discusses icky stomach stuff. If you are easily offended (or fall asleep at the boring bits) please, SKIP THE NEXT SECTION!
Tablet Coating and YOU!
We typically only see things when they go in and when they come out (ew!), but think about it: when you swallow stuff, where does it go? What exactly is the gastrointestinal tract? Here is a brief primer:
- Stomach: Acids break down what is in the stomach and some things are absorbed into the stomach lining. If television commercials are to be believed, your stomach is also the home of little blob-people who have crazy parties and make your life miserable when you eat spicy foods.
- Small intestine: There are fewer acids in here, and food is further broken down and digested (absorbed). Some of the blob-people end up here after a particularly crazy party.
- Large Intestine: The large intestine absorbs the last of the water from the matter left over and then “packages” the remaining waste for – um, oh, nevermind.
Usually active ingredients enter your body in the stomach or in the small intestine, so coatings are selected based on their rate of gastrointestinal dissolution. If a drug is to be absorbed in the stomach, a coating that dissolves quickly and easily in acid is used; but if the drug needs to make it to the small intestine before being absorbed, then an enteric coating is used.
Since the ingredients of our granulate batches are expensive, we only want to use as much as we have to (after all pharmaceutical companies – after helping people, of course – want to make wheelbarrows full of money2). Some tablets can be really small, even too small for easy consumption, and for this reason we use Fillers. Fillers must be inexpensive (of course), water-soluble (duh), inert (and compatible with the other tablet ingredients) and either yummy-tasting or (like the writer of this blog entry) tasteless.
One special type of filler is a disintegrant. Disintegrants expand and dissolve when they get wet, and assist the tablet in breaking up in the digestive tract. When that happens, the active ingredients go forth and get absorbed. Absorbed I say!
Coatings and More Coatings
Once the tablet has been coated with the filler(s), it’s time to get creative with our final tablet coatings. Here are a few examples:
Flavor – used to mask tablets that are too salty, bitter, sour or sweet.
Color – to produce a pleasant ingestion experience (oooh! lookie!) and enhance brand recognition.
Polish – a smooth (or gloss) finish that is both a part of brand recognition, and helpful when sliding down the “Old Hatch”.
Although we did not go through an exhaustive study of tablet making and coating (who would want to read that anyway?) we did go through the basics of tablet pressing and coating. We also probably learned more about the digestion system than we really wanted.
If you liked this two-part Blog Entry and would like to see more, please submit a suggestion for the next topic.
Disintegrant: From the Latin word “Disintegrate” meaning what happens when things break up into little pieces. Like when you tape some firecrackers to small plastic Army Men and blow them up. BWA-HA-HA-HA!
BWA-HA-HA-HA!: From the Latin phrase NYAH-AH-AH!
Tablet Swallow Ease Factor: Yep. I made this up. But you looked anyway, didn’t you?
Enteric: A general term for the intestines. Another interesting fact is that methane emitted from livestock is known as enteric fermentation. To show your tablet coating knowledge at the next poker game with the gang you might want to use the phrase “Excuse me, that was a bit of enteric fermentation.”
Dissolution: The act or process of resolving or dissolving into parts or elements. Also a disrespectful solution as in “Honey, I felt that turning off the TV while I was watching my favorite show was a dissolution.”
1 “Oh-HO!” I can hear you say, “If it’s THAT easy, then why was that last Blog entry so darned long?” The answer is simple: the Avanceon Institute for Making Stuff Simple has an enormous budget… and I get paid by the word.
2 And by wheelbarrows, I really mean truckloads. OK, maybe I am exaggerating here… but as a consumer who is stuck in the muck and mire of pharmaceutical products and the healthcare system, I feel I am entitled to be a bit testy.
About the Author
Neal Collier is a Principal Engineer at Avanceon, where he leads Pharmaceutical Project Teams in GxP-compliant integration solutions and validation efforts. Neal has worked on many different PLC and DCS controls platforms - and their associated HMI or SCADA visualization packages - utilizing complex programming methodologies and strategies.
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