PEG – Strange polymer

As part of a regular medical screening I got to drink a gallon of what we in the family like to call “The Sludge”. It is, IMHO, one of the least pleasant laxatives on the planet. The first 2 times I had it, it was flavored with artificial pineapple. It took me nearly 3 years to get back to where I could eat pineapple again and not have a gag reflex… My third exam, I talked the Doc into doing a different “prep”. It worked MUCH better for me. A caster oil derived laxative after a 48 hour fast. For me, much easier to simply not eat for a couple of days and swallow one small dose, than to drink The Sludge…

So this time I was not dealing with a private doctor, but with an HMO. Explained to the “clerk on the phone” my desire for ‘the other prep’ and got ‘nice sounds’ and not much else. Told to pick up my prescription at the pharmacy counter. It was The Sludge. As there is zero contact with the Doctor prior to the procedure, hard to explain things like “I have an intense gag reflex just at the thought of the stuff, now.” Oh Well… Suck it up and choke it down…

So I mix this batch of The Sludge. Pour the first glass. This batch is a different brand, and flavored Lemon instead. Oh Good, at least that Smell & Gag reflex is going to be less. Lifting the glass, a small choking feeling starts in the throat… It’s going to be a long night, I think…

Well, the good news is that I managed to drink the whole gallon of The Sludge. (Or, more accurately, the 4 liters).

There were a couple of things that made that possible. One was the less pronounced flavoring. The other two were the directions given on how to take it, and an innovation of mine. Hopefully this will help anyone else who has a similar problem…

My innovation was trivial. After each drink, I’d immediately rinse the mouth out. No lingering flavor or texture to start a cycle of reaction. I’d also take three deep breaths prior to picking up the glass, and not breath while drinking. Suppressing my normal ‘inhale the aroma’ as the glass comes to the lips prior to the first sip. No breathing until the glass is down. So no (or very reduced) smell trigger either. Basically limiting exposure to smell and taste triggers. Just a bland liquid feeling. That helped. The deep breathing also gave me a moment to shut down any mental reaction that might be starting. To plant a small suggestion that it was a simple and easy drink of mostly water.

Their directions also helped. Instead of the usual ‘drink it in one long session’ with any sized drinks / sips; they said to drink it in two specific sessions. 9 to 11 pm, then 6 to 8 am. 1/2 gallon each, and to NOT sip it, but drink 8 ounce glasses at a time. That’s 4 pints in each session. For most of them I’d do 1 cup each, but for a couple I did a whole pint in one ‘go’ (stopping and rinsing in the middle as the stuff was cold and giving a bit of ‘brain freeze’ if a whole pint was slugged down ;-) So max of 8 ‘drinks’, most often just 6 ish. Then a long break… That prevented the tendency to build up a negative response to The Sludge.

With luck, I won’t need to do this again for another decade… but it’s nice to know that I can. I’d still rather have the other approach, but this was workable. (For the terminally curious, I’m OK and with nothing outside of normal.)

But along the way, I got to wondering “What is this stuff?”

PEG – Polyethylene glycol

There’s a wiki for it:

https://en.wikipedia.org/wiki/Polyethylene_glycol

It comes in many ‘lengths’ of polymer, and it is noted in the name. In this case it was 3350. That’s the weight in Daltons (or approximately the number of hydrogens to make the same weight as a Dalton is 1/12 of a C12 mass). So about 230 chain length. Yes, a plastic polymer. So most likely my ‘reaction’ was more to the forced feeding of a crappy fake pineapple flavor than to the active ingredient. (Next time I may just try leaving the ‘flavor packet’ out altogether…)

The wiki lists an amazing litany of uses for various lengths of this polymer. Essentially a polymer ether.

Polyethylene glycol (PEG) is a polyether compound with many applications from industrial manufacturing to medicine. The structure of PEG is (note the repeated element in parentheses):

H-(O-CH2-CH2)n-OH

PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight.

Available forms and nomenclature

PEG, PEO, or POE refers to an oligomer or polymer of ethylene oxide. The three names are chemically synonymous, but historically PEG has tended to refer to oligomers and polymers with a molecular mass below 20,000 g/mol, PEO to polymers with a molecular mass above 20,000 g/mol, and POE to a polymer of any molecular mass. PEG and PEO are liquids or low-melting solids, depending on their molecular weights. PEGs are prepared by polymerization of ethylene oxide and are commercially available over a wide range of molecular weights from 300 g/mol to 10,000,000 g/mol. While PEG and PEO with different molecular weights find use in different applications, and have different physical properties (e.g. viscosity) due to chain length effects, their chemical properties are nearly identical.

So it’s really a family of compounds of wildly varying size. Some lengths do very different things from other lengths. Still, it’s a very strange stuff. I’m going to quote the list of what this stuff does:

Research for new clinical uses

PEG, when labeled with a near-infrared fluorophore, has been used in preclinical work as a vascular agent, lymphatic agent, and general tumor-imaging agent by exploiting the Enhanced permeability and retention effect (EPR) of tumors.

High-molecular-weight PEG (e.g. PEG 8000) has been shown to be a dietary preventive agent against colorectal cancer in animal models.

The Chemoprevention Database shows PEG is the most effective known agent for the suppression of chemical carcinogenesis in rats. Cancer prevention applications in humans, however, have not yet been tested in clinical trials.

The injection of PEG 2000 into the bloodstream of guinea pigs after spinal cord injury leads to rapid recovery through molecular repair of nerve membranes. The effectiveness of this treatment to prevent paraplegia in humans after an accident is not known yet.

Research is being done in the use of PEG to mask antigens on red blood cells. Various research institutes have reported that using PEG can mask antigens without damaging the function and shape of the cell.

Research is also being done on the use of PEG in the field of gene therapy.

PEG is being used in the repair of motor neurons damaged in crush or laceration incidents in vivo and in vitro. When coupled with melatonin, 75% of damaged sciatic nerves were rendered viable.

Just amazing. Cancer preventative and it helps nerve damage heal. How in the heck?…

It also looks like the medicinal uses are especially ‘cleaned up’ from the basic raw product:

PEG is soluble in water, methanol, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. It is coupled to hydrophobic molecules to produce non-ionic surfactants.

PEGs contain potential toxic impurities, such as ethylene oxide and 1,4-dioxane. Ethylene Glycol is nephrotoxic if applied to damaged skin.

But soluble in one heck of a lot of different solvents. One wonders how it interacts with cells.

We are clearly exposed to a lot of this stuff. It looks like it generally does “good stuff”, but only if the contaminants are fully removed (I’d speculate).

PEGs and methoxypolyethylene glycols are manufactured by Dow Chemical under the tradename Carbowax for industrial use, and Carbowax Sentry for food and pharmaceutical use. They vary in consistency from liquid to solid, depending on the molecular weight, as indicated by a number following the name. They are used commercially in numerous applications, including as surfactants, in foods, in cosmetics, in pharmaceutics, in biomedicine, as dispersing agents, as solvents, in ointments, in suppository bases, as tablet excipients, and as laxatives. Some specific groups are lauromacrogols, nonoxynols, octoxynols, and poloxamers.

Macrogol, used as a laxative, is a form of polyethylene glycol. The name may be followed by a number which represents the average molecular weight (e.g. macrogol 4000, macrogol 3350 or macrogol 6000).

From soaps to solvents to cosmetics and medicines. Even in jugs of The Sludge…

It is also used in a heck of a lot of common medical treatments. One wonders if they also have any cancer preventative side effects or help any kinds of injury to heal…

Medical uses

PEG is the basis of a number of laxatives (e.g., macrogol-containing products, such as Movicol and polyethylene glycol 3350, or SoftLax, MiraLAX, or GlycoLax). Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy. The preparation is sold under the brand names GoLYTELY, GaviLyte C, NuLytely, GlycoLax, Fortrans, TriLyte, Colyte, Halflytely, Softlax, Lax-a-Day, ClearLax and MoviPrep. In the United States, MiraLAX and Dulcolax Balance are sold without prescription for short-term relief of chronic constipation. Miralax is currently FDA approved for adults for a period of seven days, and is not approved for children. A 2007 comparison showed that patients suffering from constipation had a better response to these two medications than to tegaserod. These medications soften the fecal mass by osmotically drawing water into the GI tract. It is generally well tolerated, however, side effects are possible bloating, nausea, gas, and diarrhea (with excessive use).

When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood. This makes for a longer-acting medicinal effect and reduces toxicity, and allows longer dosing intervals. Examples include PEG-interferon alpha, which is used to treat hepatitis C, and PEGfilgrastim (Neulasta), which is used to treat neutropenia. It has been shown that polyethylene glycol can improve healing of spinal injuries in dogs. One of the earlier findings, that polyethylene glycol can aid in nerve repair, came from the University of Texas (Krause and Bittner). Polyethylene glycol is also commonly used to fuse B-cells with myeloma cells in monoclonal antibody production.

PEG is used as an excipient in many pharmaceutical products. Lower-molecular-weight variants are used as solvents in oral liquids and soft capsules, whereas solid variants are used as ointment bases, tablet binders, film coatings, and lubricants.

PEG is also used in lubricating eye drops.

So very widely used. One can only wonder if the laxative length also has any anti-bowl-cancer effects or if the 8000 size can act as a laxative ( I’d expect it would as it ought to suck water up too). Could it be as simple as just taking a bit of this stuff as a laxative every day or two to reduce rates of colon cancer?

Enquiring minds want to know… leave no rat unturned… or something like that.
(Now where did I leave my rat cage… ;-)

Though the idea of a cage full of rats on a laxative diet is, er, um… disturbing. Don’t know that I’d want them on a running wheel when they are, um, ‘running’ ;-)

Yet it has even more uses not related to medicines and biology:

Chemical uses

Polyethylene glycol has a low toxicity and is used in a variety of products. The polymer is used as a lubricating coating for various surfaces in aqueous and non-aqueous environments.

Since PEG is a flexible, water-soluble polymer, it can be used to create very high osmotic pressures (on the order of tens of atmospheres). It also is unlikely to have specific interactions with biological chemicals. These properties make PEG one of the most useful molecules for applying osmotic pressure in biochemistry and biomembranes experiments, in particular when using the osmotic stress technique.

Polyethylene glycol is also commonly used as a polar stationary phase for gas chromatography, as well as a heat transfer fluid in electronic testers.

PEO (polyethylene oxide) can serve as the separator and electrolyte solvent in lithium polymer cells. Its low diffusivity often requires high temperatures of operation, but its high viscosity – even near its melting point – allows very thin electrolyte layers to be created. While crystallization of the polymer can degrade performance, many of the salts used to carry charge can also serve as a kinetic barrier to the formation of crystals. Such batteries carry greater energy for their weight than other lithium ion battery technologies.

PEG has also been used to preserve objects that have been salvaged from underwater, as was the case with the warship Vasa in Stockholm, the Mary Rose in England and the Ma’agan Michael Ship in Israel. It replaces water in wooden objects, making the wood dimensionally stable and preventing warping or shrinking of the wood when it dries. In addition, PEG is used when working with green wood as a stabilizer, and to prevent shrinkage.

PEG is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.

PEG derivatives, such as narrow range ethoxylates, are used as surfactants.

PEG has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.

Biological uses

PEG is commonly used as a precipitant for plasmid DNA isolation and protein crystallization. X-ray diffraction of protein crystals can reveal the atomic structure of the proteins.

Polymer segments derived from PEG polyols impart flexibility to polyurethanes for applications such as elastomeric fibers (spandex) and foam cushions.

In microbiology, PEG precipitation is used to concentrate viruses. PEG is also used to induce complete fusion (mixing of both inner and outer leaflets) in liposomes reconstituted in vitro.

Gene therapy vectors (such as viruses) can be PEG-coated to shield them from inactivation by the immune system and to de-target them from organs where they may build up and have a toxic effect. The size of the PEG polymer has been shown to be important, with larger polymers achieving the best immune protection.

PEG is a component of stable nucleic acid lipid particles (SNALPs) used to package siRNA for use in vivo.

In blood banking, PEG is used as a potentiator to enhance detection of antigens and antibodies.

When working with phenol in a laboratory situation, PEG 300 can be used on phenol skin burns to deactivate any residual phenol.

Commercial uses

PEG is the basis of many skin creams (as cetomacrogol) and sexual lubricants (frequently combined with glycerin).

PEG is used in a number of toothpastes as a dispersant. In this application, it binds water and helps keep xanthan gum uniformly distributed throughout the toothpaste.

PEG is also under investigation for use in body armor, and in tattoos to monitor diabetes.

In low-molecular-weight formulations (i.e. PEG 400), it is used in Hewlett-Packard designjet printers as an ink solvent and lubricant for the print heads.

PEG is also one of the main ingredients in paintball fills, due to its thickness and flexibility. However, as early as 2006, some Paintball manufacturers began substituting cheaper oil-based alternatives for PEG.

PEG is a major ingredient in e-liquid, used in electronic cigarettes. It is generally used as a 30%–50% proportion of the liquid that is vaporized. Its use is designed to give a smoother effect to the vaporizing action.

PEG is also used as an anti-foaming agent in food – its INS number is 1521 or E1521 in the EU.

Industrial uses

Nitrate ester-plasticized polyethylene glycol is used in Trident II ballistic missile solid rocket fuel.

Dimethyl ethers of PEG are the key ingredient of Selexol, a solvent used by coal-burning, integrated gasification combined cycle (IGCC) power plants to remove carbon dioxide and hydrogen sulfide from the gas waste stream.

PEG has been used as the gate insulator in an electric double-layer transistor to induce superconductivity in an insulator.

PEG is also used as a polymer host for solid polymer electrolytes. Although not yet in commercial production, many groups around the globe are engaged in research on solid polymer electrolytes involving PEG, with the aim of improving their properties, and in permitting their use in batteries, electro-chromic display systems, and other products in the future.

Quite a list!

I’m sure part of the breadth comes from the many molecular weights possible and the branched vs not branched leading to many different properties.

But come on, you have to admit is an impressive range of uses. From ballistic rocket fuel to sex lube? And prevents cancer in rats while promoting damaged nerve healing? Body armor and inject ink? Sheesh. Sure looks like a ‘miracle stuff’.

I would never have thought it could do so much; when as far as I was concerned, it was just The Sludge, and 240 grams of it in a gallon of water sucks you dry and gives the Super Trots….

Now I’m pondering if you can use laxatives to make a sodium battery at home, or if you could prevent skin cancer with a layer of sex lube… That kind of n x n matrix can drive a creative mind just a tiny bit around the bend. ;-)

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