Alcohols are organic substances which contain an OH(oxygen-hydrogen) functional group. Ethanol (CH3CH2OH) is the alcohol found in alcoholic beverages and in some pharmaceutical preparations. Ethanol is also used as an industrial solvent. Alcohols are important in chemical synthesis because the alcohol (OH) functional group can be converted into other functional groups such as ketones, alkenes, haloalkanes, carboxylic acids, esters and aldehydes. These functional groups can also be converted into alcohols.

Alcohol and water are the most frequently used solvents for drug extraction from plant and animal sources. These processes involve a raw plant or animal material being ground up, and then being placed into a solvent such as alcohol to extract the required active ingredients from the source material. Alcohol is often a preferred solvent compared to water because of its antimicrobial properties, better organic solubility, and because it dose not create a residue upon standing. A mixture of water and alcohol is often used. Some substances such as flavorants, preservatives, drugs and other excipients are soluble only in alcohol and not in water.

Alcohol is used as a pharmaceutical excipient. It is used as a preservative to protect against microbial growth. It is often combined with parabens or benzoate's for this purpose. Alcohol is often an ingredient in pharmaceutical preparations such as solutions, syrups, elixirs, and tinctures. In order for alcohol to have antimicrobial preservative properties in a syrup, it has to have an alcohol content of at least 15-20%. In syrups, this level is not usually attained and therefore other preservatives such as sodium benzoate or parabens must be added. In syrups, alcohol mainly assists in dissolving the medication. Elixirs vary greatly in alcohol content depending on the solubility of the ingredients to be incorporated. For alcohol to exhibit adequate antimicrobial properties in an elixir, the alcohol content should be over 10%. Tinctures tend to have the highest alcohol content which is typically between 15-80%. Tinctures are self preserving, and therefore they do not require the addition of other antimicrobial ingredients.

Alcohol USP contains between 94.9%-96% ethanol (CH3CH2OH).

Dehydrated Alcohol USP contains 99.5% ethanol (CH3CH2OH).

Rubbing Alcohol

Rubbing alcohol is commonly used as a rubifacient, a disinfectant for the skin and for medical instruments, and for soothing the skin. It contains ethanol(70%), stabilizers, perfume oils, water, and denaturants. 23-H is the denaturant typically used, it contains acetone and methyl isobutyl ketone, which make it virtually impossible to distill or separate the ethanol and use it for other purposes such as consumption. Rubbing Alcohol also contains denatonium benzoate(1.4mg) or sucrose octacetate (355mg) for the purpose of making the taste extremely bitter and unpalatable.

Diluted Alcohol

Diluted alcohol NF consists of a mixture of alcohol USP and Purified Water USP. Equal volumes of each substance is added to the mixture, however, the mixture has a contraction effects upon mixing, and therefore the resulting volume is slightly smaller then the sum of the two added volumes, and the concentration of alcohol is slightly stronger then would be expected. As an example, if 50ml of alcohol USP and diluted water USP are mixed, the resulting volume will be 97ml and the alcohol strength would be around 49-50%.

Isopropyl Rubbing Alcohol

Isopropyl Rubbing Alcohol is commonly used as a rubifacient, disinfectant, for soothing the skin, and as a pharmaceutical vehicle to carry topical medications. It contains 70% alcohol and water and may or may not contain other ingredients such as stabilizers, perfume oils, or coloring agents.

Alcohol content limits for OTC products:

under 6 years old: 0.5% alcohol content limit

6-12: 5% alcohol content limit

over 12 and adults, 10% alcohol content limit

Chemistry

The OH functional group of alcohol is significant because it exhibits polarity. With the oxygen being more electronegative than the hydrogen atom, it pulls the electron density toward itself giving it a partial negative charge, and leaving the hydrogen atom with a partial positive charge. For this reason, alcohol molecules interact with the partial positive charge of the hydrogen on one water molecule, interacting with the partially negatively charged oxygen on another alcohol molecule forming a hydrogen bond similar to the hydrogen bonds seen in water. This is also known as a dipole-dipole interaction. The strength of this hydrogen bond is not as strong as a covalent bond, yet stronger the the van der waal force interactions seen in completely non polar molecules. The more polar groups a molecule has, the more water soluble it is. If a molecule is very small and has a polar group, it is likely to be very water soluble compared to the same molecule with a large non polar region attached.

Alcohols can act as weak acids and weak bases by accepting or donating a proton onto the oxygen atom in the OH functional group. Acidity of the alcohol is related to the degree in which the resulting conjugate base is stable and can be dissolved in water. For alcohols with very small alkyl groups attached to the OH functional group, this conjugate base is very stable and well surrounded by water and dissolved, making a stronger acid. When the alkyl group is very long, it is less water soluble and therefore less acidic. Alcohols donate and accept protons from water molecules and hydronium ions.

PKA Values:

Methanol (CH3OH): 15.5

Ethanol (CH3CH2OH): 15.9

2- Propanol ((CH3)2CH2OH): 17

2Methyl2Propanol((CH3)3COH: 18


Alcohol Consumption and Health

It is recommended to consume 2 or less alcoholic drinks per day for males, and 1 or less alcohol drinks per day for women.

Some research has shown that even moderate or low alcohol consumption may do more harm than good for a variety of reasons including increasing the risk of cancer and atrial fibrillation. It can increase the risk of cardiomyopathy at high levels. Other studies have shown benefits on vascular cardiac health of limited alcohol consumption. Alcohol has arrhythmogenic properties though a variety of mechanisms which can induce cardiac arrhythmias of the heart's electrical system. Alcohol consumption also leads to increases in blood pressure. If left untreated high blood pressure can eventually lead to strokes, heart attacks and other conditions.

Alcoholic cirrhosis of the liver is very common in frequent alcohol consumers and can result in liver cancer. Constant alcohol consumption inflames the liver, leading to fibrosis and can cause liver failure.

Alcohol has negative effects on the gastrointestinal tract including gastritis, stomach ulcers, colon cancer, and inflammation of pancreas. Alcohol also decreases absorption of essential nutrients such as calcium, magnesium, iron and zinc, putting the drinker at risk to bone mass losses or osteoporosis.

Binge drinking has shown to cause many detrimental cognitive effects such as shrinking of the brain, black outs, anxiety, other mental health disorders, brain damage, substance abuse, dependency, addiction, and memory loss.

Alcohol has been shown to increase the risk of a variety of cancers.

People who often consume a lot of alcohol have a higher change of getting lung infections.


Sources

1. Allen, Loyd V., and Howard C. Ansel. Ansel's Pharmaceutical Dosage Forms and Drug Delivery Systems (10th Edition). Baltimore, MD: Wolters Kluwer Health, 2014. Print.

2. Brown, William Henry, Brent L. Iverson, Eric V. Anslyn, and Christopher S. Foote. Organic Chemistry. Australia: Cengage Learning, 2009. Print.

3. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015–2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/.

4. National Institute of Health. Health Risks and Benefits of Alcohol Consumption. Alcohol Research and Health. Vol 24, No. 1, 2000.