2187 Chemistry and Medicines

Chemicals in medicines The words ‘medicine’ and 'drug' are often used in our country to mean the same substances: any substance, manufactured artificially, which can help recovery from sickness, relieve symptoms or modify a natural process in the body. A medicine is often a mixture of several chemical compounds. Even if it has only one active component compound often other substances are used as fillers or binders to give it bulk. Chemistry, the science r elated to chemical substances, provides us the tools to make and study the substances that are the constituents of almost all medicines. The past hundred years or so, ever since the advent of organic chemistry, many chemical compounds have been discovered in nature that are effective for curing diseases. Modern chemistry has also made it possible to synthesize several medicines using methods of organic chemistry. The most common medicines can be classified classified into few groups, groups, e.g. antibiotics, antiseptics, antiseptics, analgesics, tranquillizers, antipyretics, hormonal, steroids etc. There are very many medicines that come under each of these groups. Often several chemical compounds that make a particular group of medicines, say antibiotics have similar chemical structure. Since the medicines in a particular group are effective for treating a particular type of ailment or disease, their mode of action can also be very similar. But, the methods used to isolate a medicine from its natural sources or to synthesize it are most often very different.

ANTIBIOTICS Our body and our domestic animals, can serve as hosts to a wide variety of diseasecausing organisms (pathogens ): These are: • • • •

bacteria viruses fungi protozoon’s

An antibiotic (Greek anti, "against"; bios, "life"), is a chemical substance produced by one organism that is destructive to another. This process traditionally has been called antibiosis and is the opposite of symbiosis. More specifically, an antibiotic is a type o f chemotherapeutic agent that has a toxic effect on certain types of disease-producing microorganisms without acting dangerously on the patient. The definition most used for antibiotics is: any substance produced by a microorganism which harms or kills another microorganism. However, antibiotics DO NOT harm viruses . Doctors often prescribe antibiotics when you may have a viral infection because of the possibility that you may also acquire a bacterial infection because you are so ill with a virus - being ill places a

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person at risk for certain bacterial infections that are n ormally handled without any problem. The overwhelming majority of antibiotic substances are natural products that certain bacteria and fungi (molds) produce and send outside of their cells. About 90% of the antibiotics in use today, are isolated from bacteria. The re are a few antibiotics, however, which are completely synthetic... that is, are made from scratch in the laboratory. These particular antibiotics are designed to inhibit some process previously identified to be completely unique to bacteria, and necessary for the bacterium to remain alive. An antibiotic can be most often o ften classified into any one of the following categories o f chemical compound: 1. 2. 3. 4. 5. 6.

Amin Amino o gly glyco cosi side dess Gly Glycope copept ptiides des Beta Beta Lactams Lactams also also known known as as Penici Penicilli llin’s n’s Tet Tetracy acycli cline Quinol nolines nes Sulf ulfonam onamiides des

Amino glycosides Amino glycosides are antibiotics that are often administered into veins or muscle to treat serious bacterial infections infections.. Some amino glycosides are also used orally to treat intestinal infections or topically to treat eye infections. Some very popular examples of this group of antibiotics are • • • •

Streptomycin Kanamycin Neomycin Gentamycin

They are the inhibitors of protein synthesis, ↓ 30S ribosomal subunit , but some abnormal proteins insert in cell membrane & form pores, thus become bactericidal The chemical structure of this group of antibiotics is:













Glycopeptides Glycopeptide antibiotics are a class of antibiotic drugs. They consist of a glycosylated cyclic or polycyclic nonribosomal peptide. peptide. Important glycopeptide antibiotics include vancomycin, vancomycin, teicoplanin, teicoplanin, ramoplanin, ramoplanin, and decaplanin.

This class of drugs inhibits the synthesis of cell walls in susceptible microbes by inhibiting peptidoglycan synthesis. Bacterial cell wall contains peptidoglycan strands • • •

Peptidogly Peptidoglycan can is composed composed of UDP-N-acet UDP-N-acetyl-m yl-murami uramicc acid, acid, UDP-N-acet UDP-N-acetylylglucosamine & a pentapeptide Cycloserine, resembles to alanine & inhibits addition of alanine into peptide chain Vancomycin inhibits transglycosidase enzyme & prevents peptidoglycan chain elongation

Due to their toxicity, their use is restricted to those patients who are critically ill or who have a demonstrated hypersensitivity to the β-lactams. The chemical structure of a glycopeptide antibiotic is













Penicillin Penicillin is one major class of antibiotics. They are used to treat strep throat and countless other infections. Examples of various kinds of p enicillin include Amoxicillin, Amoxicillin, Ampicillin, Ampicillin, Carbenicillin, Carbenicillin, Cloxacillin, Cloxacillin, Dicloxacillin, Dicloxacillin, Flucloxacillin.. They are the inhibitors of cross linking of pep tidoglycan strands: • • • • •

Inhibit transpeptidase enzyme , involved in cross linking of peptidoglycan strands Also called as transpeptidation reaction & strengthens cell wall. Defect Defectss in the the synthe synthesis sis of of cell cell wall wall cause cause whole wholess in cell cell wall wall & change changess in permeability Lead Leadin ing g to bact bacter eria iall swe swell llin ing g & lys lysis is Hence cell wall synthesis inhibitors are bactericidal

Common structural features of Beta-Lactams;













Tetracycline Tetracyclines are another category of antibiotics. In addition to being used to treat infections, they are often used to manage acne. A few of the tetracyclines frequently used are:   

Achromycin V (Tetracycline) Minocin (Minocycline) Vibramycin (Doxycycline)

They are the inhibitors of protein synthesis, ↓ 30S ribosomal subunit & are bacteriostatic The chemical structure of most tetracycline is related to the following structure. The name is derived from the fact that it is made up of four rings (cycles).

Quinolones The quinolones are a family of broad-spectrum antibiotics. The parent of the group is nalidixic acid. The majority of quinolones in clinical use belong to the subset of fluoroquinolones , which have a fluoro group attached the central ring system. Quinolones and fluoroquinolones are bactericidal d rugs, actively killing bacteria. Quinolones inhibit the bacterial DNA gyrase or the topoisomerase II enzyme, thereby inhibiting DNA replication and transcription. They are the inhibitors of DNA replication & mitosis, inhibit bacterial topisomerase-II [ in gram (-) bacteria] & topoisomerase IV [in gram (+) bacteria], inhibit DNA replication & are bactericidal The common chemical structure is as follows













Sulfonamides Sulfonamide drugs (known widely as "sulfa drugs") were the first antibacterial antibiotics, and paved the way for the antibiotic revolution in medicine. The first sulfonamide was trade named Prontosil, which is a prodrug. Experiments with Prontosil began in 1932 in the laboratories of the Bayer Corporation, a component of the huge German chemical trust IG Farben. The dye-based d ye-based drug was synthesized by Bayer chemist Josef Klarer and tested in animals under the direction of physician/researcher Gerhard Domagk. Domagk quickly won the 1939 Nobel Prize in Medicine and Physiology, an honor that Hitler forbade him to accept. They are the inhibitors of DNA & cell division, can affect microbial DNA & cell division in following ways: •

Inhi nhibit bit DN DNA synt synthe hesi siss

a) Inhibitors of folate synthesis- Sulfonamides & sulfones inhibit dihydropteroate synthase (DHPS) enzyme Trimethoprim inhibits dihydro-folate reductase (DHFR) enzyme (bacterial DHFR more than human)

b) Inhibitors of thymidylate synthesis- Flucytosine : is a cytosine analogue & inhibits thymidylate synthase (TS) • • •

Converted in fungi & GI flora to 5-fluorouracil (5-FU) 5-FU converted to 5-FdUMP 5-FdUMP incorporated to DNA

Some examples of sulfonamide antibiotics are: Mafenide, Mafenide, Sulfacetamide, Sulfacetamide, Sulfamethizole, Sulfanilimide, Sulfanilimide, Trimethoprim etc.















How Antibiotics act. Antibiotics attack a metabolic pathway found in the bacterium but not in the host. This is not an insurmountable problem for bacterial pathogens because they differ in many respects from eukaryotes. Thus pencillins (betalactams) work by interfering with the synthesis of the bacterial cell walls — a structure that is not found in eukaryotes. The walls of bacteria are made of a complex polymeric material called peptidoglycan. It contains both amino acids and amino sugars. The amino sugars are of two kinds • •

N-acetylglucosamine (NAG) and its close relative N-acetylmuramic acid (NAM).

These two form a linear polymer of NAG alternating with NAM. They are linked by a glycosidic bond between the #1 and #4 carbons (this is the linkage attacked by lysozyme) and are oriented in the same way they are in cellulose. Side chains containing 4 or 5 amino acids are attached to each NAM. These form covalent bonds with amino acids in adjacent chains. The bonds may • • •

be direct to the next chain or include additional peptide cross bridges (e.g., 5 glycine residues) which extend to chains in the same plane (shown here) as well as to chains













The aminoglycosides bind to the 30S subunit of the bacterial ribosome, because the bacterial ribosome differs in several ways from the eukaryotic ribosome and thus interferes with the formation of the initiation complex , causing misreading of the mRNA. Tetracyclines also bind to the 30S subunit of the bacterial ribosome. They prevent the transfer of activated amino acids to the ribosome so protein synthesis is halted.

The fluoroquinolones block the action of two bacterial topoisomerases — enzymes that relieve the coils that form in DNA when the helix is being opened in preparation for replication or transcription or repair. block the synthesis of folic acid. Mammals ignore PABA an d its analogs and thus can tolerate sulfa drugs. The mode of action of Sulfonamides is a bit different. Both bacteria and their human hosts require folic acid for nucleic acid synthesis (it is converted into prunes into prunes and thymidine) thymidine) as well as protein synthesis (precursor of the amino acids methionine and glycine). glycine). However, bacteria synthesize their folic acid starting with para-aminobenzoic acid (PABA), while we must ingest our folic acid already formed; that is, for us it is a vitamin .

Production of antibiotics Since the first pioneering efforts of Florey of Florey and Chain in 1939, the importance of antibiotics to medicine has led to much research into discovering and producing them. The process of production usually involves screening of wide ranges of microorganisms, testing and modification. Production is carried out using fermentation; fermentation; a process that is important in anaerobic conditions when there is no oxidative phosphorylation to maintain the production of ATP by glycolysis. glycolysis.

ANALGESICS













Thus acetylsalicylic acid (commonly known as aspirin) is a salicylate with the chemical structure:

Aspirin is commercially synthesized using a two-step process. First, phenol (generally extracted from coal tar) is treated with a sodium base generating sodium phenoxide, which is then reacted with carbon dioxide under high temperature and pressure to yield salicylate, which is acidified, yielding salicylic acid. This process is known as the KolbeSchmitt reaction.













ANTISEPTICS Antiseptics are antimicrobial substances that are applied to living tissue/ tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. They should generally be distinguished from antibiotics that destroy microorganisms within the body, and from disinfectants, disinfectants, which destroy microorganisms found on non-living objects. Some antiseptics are true germicides true germicides,, capable of destroying microbes ( bactericidal), bactericidal), whilst others are bacteriostatic are bacteriostatic and only prevent or inhibit their growth. Antibacterial growth. Antibacterial are are antiseptics that only act against bacteria.

Some chemical compounds/groups of chemical substances that are often used as antiseptics are: •

•

•

Alcohols Most commonly used is ethanol (60-90%), 1-propanol (60-70%) and 2 propanol/isopropanol (70-80%) or mixtures of these alcohols. They are co mmonly referred to as "surgical alcohol". Used to disinfect the skin before injections are given, often along with iodine (tincture (tincture of iodine) iodine) or some cationic surfactants (benzalkonium chloride 0.05 - 0.5%, chlorhexidine 0.2 - 4.0% or octenidine dihydrochloride 0.1 - 2.0%). Quaternary ammonium compounds They include the chemicals benzalkonium chloride (BAC), cetyl trimethylammonium bromide (CTMB), cetylpyridinium chloride , cetylpyridinium chloride (CPC) and benzethonium and benzethonium chloride (BZT). Benzalkonium chloride is used in some pre-operative skin disinfectants (conc. 0.05 - 0.5%) and antiseptic towels. The antimicrobial activity of Quats is inactivated by anionic surfactants, surfactants, such as soaps. Related disinfectants include chlorhexidine and octenidine. Boric acid













Used as a 6% (20Vols) solution to clean and deodorise wounds and ulcers. More common 1% or 2% solutions of hydrogen peroxide have been used in household first aid for scrapes, etc. However, even this less potent form is no longer recommended for typical wound care as the strong oxidization causes scar formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice. •

•

•

Iodine Usually used in an alcoholic solution (called tincture of iodine) iodine) or as Lugol's iodine solution as a pre- and post-operative antiseptic. No longer recommended to disinfect minor wounds because it induces scar tissue formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice. Novel iodine antiseptics containing iodopovidone/PVP-I (an iodophor , complex of povidone, a water-soluble polymer , with triiodide anions I3-, containing about 10% of active iodine, with the commercial name Betadine) are far better tolerated, don't affect wound healing negatively and leave a depot of active iodine, creating the so-called "remanent," or persistent, effect. The great advantage of o f iodine antiseptics is the widest scope of antimicrobial activity, killing all principle pathogens and given enough time even spores, which are considered to be the most difficult form of microorganisms to be inactivated by disinfectants and antiseptics. Mercurochrome Not recognized as safe and effective by the U.S. Food and Drug Administration (FDA) due to concerns about its mercury content. Another obsolete organomercury antiseptics include bis-(fenylmercury) monohydrogenborate . Phenol (carbolic acid) compounds Phenol is germicidal in strong solution, inhibitory in weaker ones. Used as a "scrub" for pre-operative hand cleansing. Used in the form of a powder as an antiseptic baby powder, where it is dusted onto the belly button as it heals. Also used in mouthwashes and throat lozenges, where it has a methadone-like painkilling effect as well as an antiseptic one. Example: TCP. TCP. Other phenolic















DISINFECTANTS By the middle of the nineteenth century, post-operative sepsis infection accounted for the death of almost half of the patients undergoing major surgery. In 1839 the chemist Justin von Liebig had asserted that sepsis was a kind of combustion caused by exposing moist body tissue to oxygen. It was therefore considered that the best prevention was to keep air away from wounds by means of plasters, collodion or resins. Germ Connection with wound sepsis

When, in 1865, Louis Pasteur suggested that decay was caused by living organisms in the air, which on entering matter caused it to ferment, Lister made the connection with wound sepsis. A meticu meticulou louss resear researcher cher and surgeon surgeon,, Lister Lister recogni recognized zed the relati relations onship hip betwee between n Pasteur's research and his own. He considered that microbes in the air were likely causing the putrefaction and had to be destroyed before they entered the wound. In the previous year Lister had heard that 'carbolic acid' was being used to treat sewage in Carlise, and that fields treated with the affluent were freed of a parasite causing disease in cattle.













Antiseptics: An agent that inhibits or destroys microorganisms on living tissue including skin, oral cavities and open wounds. Chemical disinfectants: A chemical agent used on inanimate surfaces and objects to destroy infectious fungi, viruses and bacteria but not necessarily their spores. Sporicidal and antiviral agents may be considered a special class of disinfectants. Disinfectants are often categorized as high level, intermediate level, and low level by medically oriented groups based upon their efficacy against various microorganisms. Decontamination: The removal of microorganisms by disinfection or sterilization. Disinfectants: A chemical or physical agent that destroys or removes vegetative forms of harmful microorganisms when applied to a surface. Sanitizing Sanitizing agents: An agent which reduces microbes on inanimate surfaces, the number of all forms of microbial life including fungi, viruses and bacteria. Sporicidal agents: An agent that destroys bacterial and fungal spores when used in sufficient concentration for a specified contact time. It is expected to kill all vegetative microorganisms. Sterilants: An agent that destroys all forms of microbial life including fungi, viruses and













Salmonella etc.

7) Lipid-coated viruses

Herpes simplex virus, Hepatitis B virus, HIV

Classification Classification of Disinfectants Disinfectants Chemical Chemical disinfect disinfectant ant is classified classified by their chemical type. This includes includes Aldehydes, Aldehydes, alcohol alcohol,, haloge halogens, ns, and per-ox per-oxide ides, s, quatern quaternary ary ammoni ammonium um compoun compounds ds and phenol phenolic ic compounds. General classification of Antiseptics, Disinfectants and Sporicidal Agents. Chemical Entity 1) Aldehyd hydes

Classification Sporicidal agents

Examples 2% Gluteraldehyde

2) Alcohol

General General purpose purpose disinfecta disinfectants, nts, antiseptic antiseptic,, 70% antiviral agents. alcohol

Isopropyl













Selection of an antiseptic for hand and surgical site disinfection:

Hands and surgical sites are disinfected in a hospital setting to reduce the resident flora and to remove transient flora (e.g. (e.g. – Streptococcus pyogenes and methicillin resistant Staphylococc Staphylococcus us aureus and Pseudomonas aeruginosa) that have been implicated in hospital- associated infection. Use of antiseptic to disinfectant hands has been shown to be more effective than soap and water in reducing the counts of bacteria on the skin; repeated antiseptic use further reduces these counts. These principles may be applied to clean room operation in the pharmaceutical industry.

Mechanism of Disinfectant activity

Target Cell wall

1) 2) 3) 4)

Disinfectants

Formaldehyde, hypochlorite’s and mercurials Cyto Cytopl plas asmi micc memb membra rane ne,, acti action on on Anilides and hexachlorophene membrane potential Membrane ane enzymes, act action on Hexachlorophene electron transport chain Action on ATP Chlorhexidine and ethylene oxide Acti Action on on enzy enzyme mess with with –SH –SH gro group up Ethy Ethyle lenene-ox oxid ide, e, Glut Gluter eral alde dehy hyde, de, Hydr Hydrog ogen en













actively, so the selective pressure for the development of resistance is less profound. However, the most frequently isolated microorganism from an environmental monitoring program may be periodically subjected to use dilution testing with the agents used in the disinfection program to confirm con firm their susceptibility.

Neutralizing Agents for common Disinfectant

Disinfectant

1) 2) 3) 4) 5)

Alcohols Gluteraldhyde Sodium hypochlorite’s Chlorhexidine Mercur Mercuric ic chlori chloride de 6) Quaternaryammonium compounds

Neutralizing Agents

Dilution or polysorbate 80 Glycine and Sodium bisulfate Sodium thiosulfate Poltsorbate 80 and lecithins Thiogl Thioglyco ycolic lic acid acid Polysorbate 80 and lecithins

Because a wide range of different materials materials of constructi construction on are used in clean rooms and other controlled areas, each material needs to be evaluated separately to validate the efficacy of a given disinfectant.















APPLICATIONS OF DISINFECTANTS

Disinfectant Alcohols

Uses Ethyl or isopropyl alcohol at 70 70-80% co concentration is is a good genera generall purpos purposee disinf disinfect ectant ant;; not effect effective ive against against bacter bacterial ial spores. Phenols Effective against vegetative bacteria, fungi and viruses containing liquids, unpleasant odor. Formaldehyde Concentration of 55-8% fo formalin is is a go good di disinfectant ag against vegeta vegetati tive ve bacteri bacteria, a, spores spores and viruse viruses; s; known known carcin carcinoge ogen; n; irritating odor. Quaternary Quaternary Ammonium Ammonium Cation Cationic ic deterg detergent entss are strongl strongly y surfac surfaced ed active active;; extrem extremely ely Compounds effect effective ive agains againstt lipovi lipovirus ruses; es; ineffe ineffecti ctive ve agains againstt bacter bacterial ial













Some microorganisms are m ore resistant to disinfection disinfection than others. The generally generally accepted order from the most resistance to the least resistant is: bacterial spore, mycobacteria, hydropjillic viruses, fungi, vegetative bacteria, lipid viruses. Disinfecting a spill with a small concentration of bacterial spores will require longer disinfection time than a large concentration of lipid viruses.

4) Type and concent concentrat ration ion of dis disinf infecta ectant nt used: used:

Resistanc Resistancee of microorgan microorganisms isms depends depends on the type of disinfec disinfectan tantt used. A particul particular ar microo microorga rgani nism sm may be more resi resist stant ant to one type type of disinf disinfec ectan tantt than than anoth another. er. For instance, alcohol (Isopropyl or ethyl) is effective against vegetative bacteria and most lipophilic viruses. Many disinfectants are broad spectrum; that is, effective against all or













microorganisms need longer exposures to be killed. Higher temperature increases the killing power of most disinfectants, where lower temperature may slow the killing power of most disinfectants. . General Description of disinfectants used:

1) Incidur:

Incidur is a broad spectrum; Microbiocidal action including HIV, Hepatitis B etc.It shows long residual effect with sustained release. It is manufactured by Henkel Germany. It is purposely used for surface disinfection and fumigation.













•

Benzalkonium chloride………...0.5%

•

Emollents.

Range of Application: Industrial Industrial Quality Quality Control Control Laboratori Laboratories, es, Research Research Institutes Institutes,, Academics, Academics, Drug • Manufacturing units. Mode of Action: It generally shows action towards membrane permeability. It coagulates cellular • components. Recommended concentration and contact time (According to manufacturer): Accord According ing to manufa manufactu cturer rer (Unive (Universa rsall Healthc Healthcare are,, Silvas Silvassa) sa),, Leverm Levermed ed is •















Oxiv Oxivir ir is purpo purpose sely ly used used in Hosp Hospit ital als, s, labor laborat ator orie ies, s, Inst Instit itut utes es and and Drug Drug manufacturing units.

Recommended Concentration and contact time:  According to manufacturer (Johnson Diversy), Oxivir is effective at 2.5% for 5 minute contact time.

Mode of Action:  Oxivir shows action on enzymes with –SH group. 

4) Vi

Oxivir also cause general oxidation of cellular components. II 256: 256:















Cleaner and disinfectant

Single shot product

Time and cost effective

Range of Application:  Virex II 256 is purposely used for instruments disinfection. It is also used for













Antacids are usually taken after meals and at bedtime, or as directed by your doctor doc tor or health care professional. Take your medicine at regular intervals. Do not take your medicine more often than directed. Need to take care before taking this: •constipation













  

IgE-dependent release IgE-independent release (C3a and C5a, or drugs (e.g., d-tubocurarine). Acts as neurotransmitter in histaminergic nerves













Vasodilatation

H1

Endothelial cells

Increased Vasc. Permeability

H1 (H2?)

Endothelial cells













2nd Generation 

Key Members Desloratadine (loratadine)







































2187 Chemistry and Medicines

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