Article in Tablets and Capsules Sep 10 on external lubrication technology for tablet production

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Copyright, CSC Publishing. Tablets & Capsules
Eliminating magnesium stearate from tablets
Tablets must deliver accurate doses step takes time and ties up equipment, nesium stearate suspended in a 10 per-
of active pharmaceutical ingredients and there are costs associated with cent solution of pure ethanol. The sus-
(APIs)—typically verified by dissolu- that. It also hampers the adoption of pension is applied to the upper and
tion testing—and that requires scruti- continuous processing. Furthermore, lower punches and the die wall using
nizing the function and effectiveness the amount of lubricant added (typi- two piezo valves activated by a prox-
of every tablet excipient, including cally 0.5 to 2.0 percent w/w) tends to imity sensor. The amount of magne-
magnesium stearate. Magnesium exceed what’s needed to make a good sium stearate applied is minimal, typi-
stearate acts as a lubricant, helping tablet, which can lead to premature cally 0.03 percent w/w of the tablet.
powder formulations flow and pre- tooling wear because achieving the Furthermore, the amount can be mea-
venting tablets from binding in the die desired tablet hardness will require sured and validated. Ethanol consump-
and sticking to the upper punch. Its more compressive force. tion is typically 250 milliliters per hour
effectiveness as a lubricant has made Alternatives to adding lubricants on a tablet press operating at 100,000
magnesium stearate the most common to the blend. Since the 1960s, the tablets per hour; no ethanol residue
excipient in tablets, but it has draw- pharmaceutical industry has developed remains on the tablet. Other advan-
backs. Perhaps the most serious of several methods that reduce, if not tages of external lubrication include
these is its slowing of dissolution, eliminate, the need to add lubricants tablets that are harder than those with
which may compromise delivery of to powder blends. These include using blended lubricants and shorter dissolu-
the API. This, among other reasons, oil as a lubricant, using PTFE (Teflon) tion times. The system also reduces
has led the pharmaceutical industry to inserts on the tooling, and adding spe- lubricant consumption.
seek alternatives. cialty treatments (coatings) to the While external lubrication doesn’t
Magnesium stearate has a plate-like tooling. While each of these methods eliminate magnesium stearate, reduc-
structure that shears easily, enabling it showed some success, they also had ing it is a good first step, and it’s pos-
to reduce friction between the die wall technical limitations and/or were ex- sible that other alternative means of
and the tablet’s edge during compres- pensive. The most promising alterna- lubricating the tablet press will be-
sion and ejection. The excipient also tive was external lubrication. come available. In fact, many of us
reduces the amount of force that the The first systems to provide exter- welcome the day when magnesium
punch must apply to compress and nal lubrication (lubrication of the stearate is no longer needed at all.
eject the tablet. Furthermore, it tooling during compression) appeared T&C
reduces stress on the tablet and the in the 1990s. They used two nozzles [Editor’s Note: To comment on the Back
tablet press by preventing the tablet to continuously spray dry magnesium Page, visit www.tabletscapsules.com.]
from binding in the die and sticking to stearate onto the punch heads and die
the upper punch. Magnesium stearate walls prior to the filling stage; thus,
also increases the density of the pow- only a small amount of lubricant
der bed before compression and tends reached the tablet. These nozzles, Nic Michel is vice
to equalize pressure distribution within however, tended to get blocked, so
president, process divi-
the tablet. Both functions promote they were heated, which partially
uniform tablet density, which pro- overcame the problem. But because sion, at Oystar USA,
motes uniform bioavailability. the spray was continuous, other prob- Edison, NJ. Tel. 732
There are drawbacks, however, to lems developed: Too much magne- 343 7600, fax 732
the use of lubricants in powder blends. sium stearate was consumed; the 343 7601. Website:
The lubricant may form a barrier tablet press became “foggy” with dust;
www.oystarusa.com.
around particles that remains intact and it was difficult to measure and val-
during compression, making the idate how much lubricant each tablet The division offers
tablets hydrophobic and prolonging contained. Manesty tablet pres-
dissolution times. Lubricants may also Despite these drawbacks, the phar- ses and coaters and
interfere with particle bonding, maceutical industry remained inter- Hüttlin granulators,
thereby decreasing blend cohesive- ested in external lubrication, and bet-
dryers, and coaters.
ness, which is why lubricants are ter systems were developed, including
always blended into formulations just a system called AccuSpray that our Dipankar Dey is
prior to tabletting: to minimize their company introduced in 2007. It head of processing and
negative effects. This extra blending applies an intermittent spray of mag- validation for Oystar’s Manesty unit.