This document provides an introduction to chemotherapy. It discusses the history of chemotherapy from ancient uses of medicinal plants to treat infections to major discoveries of antibiotics in the 20th century. These include Fleming's discovery of penicillin, Waksman's discovery of streptomycin, and the mass production of penicillin during World War II. The document defines key terms related to infectious diseases and chemotherapy and outlines principles of antimicrobial therapy including mechanisms of selective targeting, therapeutic index, identification of infecting organisms, and empiric therapy prior to identification.

1. Introduction to Chemotherapy
G Vijay Narasimha Kumar
Asst. Professor,
Dept. of. Pharmacology
Sri Padmavathi School of Pharmacy

2. Overview
 Objectives
 History
 Definitions
 Important concepts
 References

3. Objectives
 To bring awareness in students regarding the significant contributions of
scientists in the emergence of Chemotherapy.
 To impart knowledge concerning key terms and concepts in chemotherapy.

4. History
 Humankind has been subject to infection by microorganisms since
before the dawn of recorded history 3 .
 Infectious diseases and cancers are among the most deadly afflictions
plaguing human societies 1.
 Antibiotics are the most frequently prescribed medications today to
treat infections although microbial resistance due to evolutionary
pressures and misuse threatens their continued efficacy 3.

5.  Centuries earlier humans had learned to use
crude preparations empirically for the topical
treatment of infections.
 Chinese used soya bean curd and moldy bread
for carbuncles & boils.
 Greeks (Hippocrates) used wine to treat wounds 2.

6. Bacteria
 Antony Leeuwenhoek was the first person to see
bacteria and he is often regarded as the “Father of
Microbiology”.
 Van Leeuwenhoek discovered "protozoa" - the
single-celled organisms and he called them
"animalcules". He also improved the microscope
and laid foundation for microbiology. He is often
cited as the first microbiologist to study muscle
fibers, bacteria and spermatozoa 5.

7. Specific infectious disease – Specific microorganism
 Robert Heinrich Herman Koch, was a
celebrated German physician, pioneering microbiologist and
founder of modern bacteriology.
 He is known for his role in identifying the specific causative
agents and for giving experimental support for the concept of
infectious disease.
 He showed that specific microorganisms could always be isolated
from the excreta and tissues of people with particular infectious
diseases and that these same microorganisms were usually
absent in healthy individuals 3,6.

8. Figure:
Koch’s
Postulates3

9.  He is well known for his role in identifying the specific causative agents
of tuberculosis, cholera, and anthrax.
 As a result of his groundbreaking research on tuberculosis, Koch
received the Nobel Prize in Physiology or Medicine in 1905 3,6 .

10. Antibiosis
 Antibiosis is a biological interaction between two or
more organisms that is detrimental to at least one of
them; it can also be an antagonistic association between
an organism and the metabolic substances produced by
another.
 Louis Pasteur reported in 1877 that when common
bacteria are introduced into a pure culture of anthrax
bacilli, the bacilli died and that an injection of deadly
anthrax bacillus into a laboratory animal was harmless if
common bacteria are injected with them 3.

11. Figure: Harposporium (centre) showing antibiosis against Paecilomyces varioti 7

12. Paul Ehlrich – Father of Chemotherapy
 Paul Ehrlich was a German physician and scientist who worked in
the fields of hematology, immunology, and antimicrobial
chemotherapy. The methods he developed for staining tissue
made it possible to distinguish between different types of blood
cells, which led to the capability to diagnose numerous blood
diseases.
 His laboratory discovered arsphenamine (Salvarsan), the first
effective medicinal treatment for syphilis, thereby initiating and
also naming the concept of chemotherapy.
 Ehrlich popularized the concept of a magic bullet.
 In 1908, he received the Nobel Prize in Physiology or Medicine for
his contributions to immunology 8.

13. Alexander Fleming
 Sir Alexander Fleming was a Scottish biologist, pharmacologist and botanist.
 Following World War I, Fleming actively searched for anti-bacterial agents, having
witnessed the death of many soldiers from sepsis resulting from infected wounds 9.
.

14.  Testing the nasal secretions from a patient with a heavy cold, he found that nasal
mucus had an inhibitory effect on bacterial growth. This was the first recorded
discovery of lysozyme, an enzyme present in many secretions including tears, saliva,
human milk as well as mucus. Lysozyme degrades the bonds in bacterial
peptidoglycan cell walls, particularly in Gram-positive organisms. Unfortunately,
lysozyme had little therapeutic potential 9.
Alexander Fleming - Lysozyme

15. Alexander Fleming - Penicillins
 Due to difficulties in cultivation and purification of penicillins, Fleming finally
abandoned penicillin.
 Not long after he did, Howard Florey and Ernst Boris Chain at the Radcliffe
Infirmary in Oxford took up researching and mass-producing it 9.
"When I woke up just after dawn on September 28, 1928, I certainly didn't
plan to revolutionize all medicine by discovering the world's first antibiotic, or
bacteria killer," Fleming would later say, "But I suppose that was exactly what I did.“

16. They started mass production after the bombing of Pearl Harbor. By D-Day in
1944, enough penicillin had been produced to treat all the wounded in 2nd world war 9.
They were awarded Nobel prize in Physiology and Medicine for the year 1945.

17. Gerhard Domagk - Sulphonamides
 Gerhard Johannes Paul Domagk was
a German pathologist and bacteriologist.
 He is credited with the discovery of Sulfonamidochrysoidine
(KI-730)– the first commercially available antibiotic (marketed
under the brand name Prontosil) – for which he received the
1939 Nobel Prize in Physiology or Medicine.
 Domagk's work on sulfonamides eventually led to the
development of the antituberculosis drugs thiosemicarbazone
and isoniazid, which helped to curb the epidemic of
tuberculosis which swept Europe after World War II 10.

18.  Selman Abraham Waksman was a Russian-born, Jewish-
American inventor, biochemist and microbiologist
whose research into organic substances, largely
into organisms that live in soil and their
decomposition promoted the discovery of Streptomycin,
and several other antibiotics such
as actinomycin, clavacin, streptothricin, grisein, neomy
cin, fradicin, candicidin, candidin etc.,
Selman Abraham Waksman - Streptomycin
 Waksman was awarded the Nobel Prize in 1952 "for his discovery of streptomycin,
the first antibiotic effective against tuberculosis."

19. In rapid succession, deliberate searches of the metabolic products
of wide variety of soil microbes led to the discovery of ---
 Trythricin – 1939
 Streptomycin – 1943
 Chloramphenicol – 1947
 Chlortetracycline – 1948
 Neomycin – 1949
 Erythromycin – 1952
These drugs ushered in the age of so called “miracle drugs”. Hence
1940-60 is called “Golden age of Anti-Microbials” 3.

20. Key Terms
 Infection is the invasion of an organism's body tissues by disease-causing agents,
their multiplication, and the reaction of host tissues to these organisms and the
toxins they produce.
 Infectious disease, also known as transmissible disease or communicable disease,
is illness resulting from an infection.
 Disease causing agent is also called infectious agent.
 A disease is a particular abnormal condition, a disorder of a structure or function,
that affects part or all of an organism. Disease is often construed as a medical
condition associated with specific symptoms and signs.
 Illness and sickness are generally used as synonyms for disease12.

21.  If the infectious agent produces no clinical evidence of disease, the infection is called
subclinical or asymptomatic.
 A detectable alteration in normal tissue function is called disease.
 Pathogenicity is the ability to produce disease; thus a pathogen is a microorgnism that
causes disease.
 True pathogen causes disease or infection in a healthy individual.
 Opportunistic pathogen causes disease only in a susceptible individuals.
 Communicable disease is the ability of the infectious agent to be transmitted to an
individual by direct or indirect contact or as an airborne infection12.
Key Terms

22. Key Terms
 A medical sign is an objective indication of some medical fact or characteristic
that may be detected and still or video photographed or audio-recorded by a patient
or anyone, especially a physician, before or during a physical examination of
a patient.
 A symptom is a departure from normal function or feeling which is noticed by
a patient, reflecting the presence of an unusual state, or of a disease. A symptom is
subjective, observed by the patient, and cannot be measured directly.
For example, whereas a tingling paresthesia is a symptom (only the person
experiencing it can directly observe their own tingling feeling), erythema is a sign
(anyone can confirm that the skin is redder than usual) 12.

23. Key Terms
 Morbidity (from Latin morbidus, meaning "sick, unhealthy") is a diseased
state, disability, or poor health due to any cause.
 A syndrome is the association of several medical signs, symptoms, and or other
characteristics that often occur together.
 Incubation period is the time between infection and the appearance of
symptoms.
 Latency period is the time between infection and the ability of the disease to
spread to another person, which may precede, follow, or be simultaneous with the
appearance of symptoms12.

24. Figure: Incubation and Latent period

25. Disease – Stages
 An acute disease is a short-lived disease, like the common cold.
 A chronic disease is one that lasts for a long time, usually at least six months. During
that time, it may be constantly present, or it may go into remission and periodically
relapse.
 A flare-up can refer to either the recurrence of symptoms or an onset of more severe
symptoms.
 A refractory disease is a disease that resists treatment, especially an individual case
that resists treatment more than is normal for the specific disease in question12.

26.  Progressive disease is a disease whose typical natural course is the worsening of the
disease until death, serious debility, or organ failure occurs.
 A cure is the end of a medical condition or a treatment that is very likely to end it.
 Remission refers to the disappearance, possibly temporarily, of symptoms12.

27. Key Terms
 Antimicrobial chemotherapy involves treatment of systemic/topical
infection using chemical agents or drugs that are selectively toxic to the causative ag-
ent of the disease, such as a virus, bacterium, or other microorganism without harming
the host cells 11.
Antimicrobial Agent
Antibacterials
(Synthetic)
Antibiotics
(Microorganisms)

28. Figure:
Venn diagram
showing
Relationship
between
antimicrobial
agents

29. Antibiotics are a broader range of antimicrobial compounds which can act on fungi,
bacteria, and other compounds. Although antibacterials come
under antibiotics, antibacterials can kill only bacteria.
There are four types of antimicrobial chemotherapy:
 Antibacterial chemotherapy, the use of antibacterial drugs to treat bacterial
infection.
 Antifungal chemotherapy, the use of antifungal drugs to treat fungal infection.
 Antiprotozoal chemotherapy, the use of antiprotozoal drugs to treat protozoan
infection.
 Antiviral chemotherapy, the use of antiviral drugs to treat viral infection 11.

30.  Antiseptics: Agents that kill or inhibit growth of microorganisms when applied to
tissues.
 Disinfectants: Agents killing or inhibiting growth of microorganisms when
applied to nonliving objects.
 Cidal (Irreversible inhibition of growth)
An agent that kills microorganisms. Bactericidal, fungicidal, viricidal…etc
e.g. Penicillin’s, Cephalosporin’s, Aminoglycosides…etc
 Static (Reversible inhibition of growth)
An agent that inhibits growth of microorganism. Bacteriostatic, fungistatic, Viristatic etc
e.g. Sulfonamides, Tetracyclines, Macrolide antibiotics…etc 11.

31. A static agent in large doses becomes cidal and cidal agents in low doses
become static. One drug ( chloramphenicol) could be bacteriostatic for one organism
(gram negative rods), & cidal for another (S. pneumoniae)1.

32. Principles of Antimicrobial therapy
 Antimicrobial therapy takes advantage of the biochemical differences that exist
between microorganisms and human beings.
 Antimicrobial drugs are effective in the treatment of infections because of their
selective toxicity; that is, they have the ability to injure or kill an invading
microorganism without harming the cells of the host 1,4 .

33. Mechanism of Selective Targeting
The goal of antimicrobial therapy is selective toxicity, i.e., inhibiting pathways or
targets that are critical to pathogen at concentrations of drug lower than those required
to affect host pathways.
Selectivity can be realized by attacking:
 Targets unique to pathogen and that are not present in the host.
 Targets in the pathogen that are similar but not identical to the host.
 Targets in the pathogen that are shared by the host but that vary in importance
between pathogen and host and thus impart selectivity 1,4.

34. S.no Type of
Targeting
Mechanism Example
1 Unique Drug targets genetic or biochemical pathways
that is unique to pathogen
Bacterial cell wall
synthesis inhibitor,
Fungal cell wall and
membrane damagers
2 Selective Drug targets protein isoform that is unique in
pathogen
Dihydrofolate
reductase inhibitors,
Protein synthesis
inhibitors
3 Common Drug targets metabolic requirements that is
specific to pathogen
Antimetabolites
Ex: 5-Flourouracil1,4
Mechanism of Selective Targeting

35. Therapeutic Index (TI)
 The ratio of toxic dose to therapeutic dose of a drug is called therapeutic index of a
drug.
 Also referred to as therapeutic window or safety window or sometimes as therapeutic
ratio 11.
TD 50
Therapeutic Index =
ED 50

36.  The TI is therefore an indication how selective the drug is in producing the desired
effects.
 A highly selective drug can often be prescribed safely because of the large difference
between its therapeutic and toxic concentrations.
 The margin of safety is less in less selective drug, because of its low therapeutic
index 11.

39. Selection of Antimicrobial agent
Selection of the most appropriate antimicrobial agent requires knowing 4 --
1) The organism’s identity.
2) The organism’s susceptibility to a particular agent.
3) The site of the infection.
4) Patient factors.
5) The safety of the agent.
6) The cost of therapy.

40. Identification of the infecting organism
 Characterizing the organism is central to selection of the proper drug.
 Body fluids that are normally sterile are taken for identification are --
Blood
Serum
Cerebrospinal fluid [CSF]
Pleural fluid
Synovial fluid
Peritoneal fluid
Urine4.
 Generally it is necessary to culture the infective organism to arrive at a conclusive
diagnosis and determine the susceptibility to antimicrobial agents. Thus, it is
essential to obtain a sample culture of the organism prior to initiating treatment.

41. Figure: Some laboratory techniques that are
useful in the diagnosis of microbial diseases 4.

42. Empiric therapy prior to identification of the organism
Ideally, the antimicrobial agent used to treat an infection is selected after the
organism has been identified and its drug susceptibility established. However, in the
critically ill patient, such a delay could prove fatal, and immediate empiric therapy is
indicated 4.

43.  Acutely ill patients with infections of unknown origin require immediate treatment.
Ex: A neutropenic patient (one who is predisposed to infections due to a reduction
in neutrophils)
A patient with meningitis
 If possible, therapy should be initiated after specimens for laboratory analysis have
been obtained but before the results of the culture and sensitivity are available 4.
Timing:

44. Drug choice in the absence of susceptibility data is influenced by the site of
infection and the patient’s history.
For example:
Previous infections Age
Recent travel history recent Antimicrobial therapy
Immune status
Whether the infection was hospital- or community-acquired
Broad-spectrum therapy may be indicated initially when the organism is
unknown or polymicrobial infections are likely 4.
Selecting a drug:

45.  The choice of agent(s) may also be guided by known association of particular
organisms in a given clinical setting.
For example,
A gram-positive cocci in the spinal fluid of a newborn infant is unlikely to be
Streptococcus pneumonia and most likely to be Streptococcus agalactiae (a group B
streptococci), which is sensitive to penicillin G.
By contrast, gram-positive cocci in the spinal fluid of a 40-year-old patient are most
likely to be S. pneumoniae. This organism is frequently resistant to penicillin G and
often requires treatment with a high-dose third generation cephalosporin (such as
ceftriaxone) or vancomycin 4.

46. After a pathogen is cultured, its susceptibility to specific antibiotics serves as a
guide in choosing antimicrobial therapy.
 Some pathogens, such as Streptococcus pyogenes and Neisseria meningitidis,
usually have predictable susceptibility patterns to certain antibiotics.
 In contrast, most gram-negative bacilli, enterococci, and staphylococcal species
often show unpredictable susceptibility patterns and require susceptibility testing to
determine appropriate antimicrobial therapy 4.
Determining antimicrobial susceptibility of infective organisms:

47.  The minimum inhibitory concentration (MIC) is the lowest antimicrobial
concentration that prevents visible growth of an organism after 24 hours of
incubation.
 This serves as a quantitative measure of in vitro susceptibility and is commonly used
in practice to streamline therapy.
 Computer automation has improved the accuracy and decreased the turnaround
time for determining MIC results and is the most common approach used by clinical
laboratories 4.
Minimum inhibitory concentration:

48. Figure: Determination of minimum inhibitory concentration (MIC) 4

49. Bacteriostatic versus bactericidal drugs 4
Bacteriostatic drugs
Arrest the growth and
replication of bacteria
Limits the spread of
infection until the immune
system attacks, immobilizes,
and eliminates
the pathogen
If the drug is removed before the
immune system
has scavenged the organisms,
enough viable organisms may
remain to begin a second cycle of
infection.
Bactericidal drugs
Kill bacteria
Eliminates infection before the
activation of the immune
system
Drugs of choice in seriously ill
and immunocompromised
patients.

50. Effect of the site of infection on therapy:
 Adequate levels of an antibiotic must reach the site of infection for the invading
microorganisms to be effectively eradicated.
 Capillaries with varying degrees of permeability carry drugs to the body tissues.
 Natural barriers to drug delivery are created by the structures of the capillaries of
some tissues, such as the
Prostate Testes
Placenta The vitreous body of the eye
Central nervous system (CNS)4.

51. Figure: Structure of a Capillary 13

52. Figure: Types of Capillaries 13

53. Figure: Types of Capillaries 13

54. CNS: Blood Brain Barrier

55. Figure: Transport mechanisms through BBB 13

56. The penetration and concentration of an antibacterial agent in the CSF
are particularly influenced by the following:
 Lipid solubility of the drug.
 Molecular weight of the drug.
 Protein binding of the drug 13

57. Patient Factors:
In selecting an antibiotic, attention must be paid to the condition of the patient.
1. Immune System:
 Elimination of infecting organisms from the body depends on an intact immune
system, and the host defense system must ultimately eliminate the invading
organisms.
 Alcoholism, diabetes, HIV infection, malnutrition, autoimmune diseases, pregnancy,
or advanced age can affect a patient’s immunocompetence, as can immunosuppressive
drugs.
 High doses of bactericidal agents or longer courses of treatment may be required to
eliminate infective organisms in these individuals13

58. 2.Renal dysfunction:
 Poor kidney function may cause accumulation of certain antibiotics.
 The number of functional nephrons decreases with age. Thus, elderly patients are
particularly vulnerable to accumulation of drugs eliminated by the kidneys.
 Dosage adjustment prevents drug accumulation and therefore adverse effects.
 Serum creatinine levels are frequently used as an index of renal function for
adjustment of drug regimens 13.

59. 3.Hepatic dysfunction:
Antibiotics that are concentrated or eliminated by the liver must be used with caution
when treating patients with liver dysfunction 13.
Ex: Erythromycin and Doxycycline.

60. 4. Poor Perfusion:
 Decreased circulation to an anatomic area, such as the lower limbs of a diabetic
patient, reduces the amount of antibiotic that reaches that area, making these
infections difficult to treat 13.

61. 5.Age:
 Renal or hepatic elimination processes are often poorly developed in newborns,
making neonates particularly vulnerable to the toxic effects of chloramphenicol and
sulfonamides.
 Young children should not be treated with tetracyclines or quinolones, which affect
bone growth and joints, respectively.
 Elderly patients may have decreased renal or liver function, which may alter the
pharmacokinetics of certain antibiotics 13.

62. 6. Pregnancy and lactation:
 Many antibiotics cross the placental barrier or enter the nursing infant via the breast
milk.
 Although the concentration of an antibiotic in breast milk is usually low, the total
dose to the infant may be sufficient to produce detrimental effects 13.

63. Figure: Maternal Intake of Drug13

64. Figure: FDA categories of antimicrobials and fetal risk.13

65. 7. Risk factors for multidrug-resistant organisms:
Infections with multidrug-resistant pathogens need broader antibiotic coverage
when initiating empiric therapy.
Common risk factors for infection with these pathogens include --
 Prior antimicrobial therapy in the preceding 90 days.
 Hospitalization for greater than 2 days within the preceding 90 days.
 Current hospitalization exceeding 5 days.
 High frequency of resistance in the community or local hospital unit.
 Immunosuppressive diseases and/or therapies 13.

66. Safety of the agent:
 Antibiotics such as the penicillins are among the least toxic of all drugs because they
interfere with a site or function unique to the growth of microorganisms.
 Other antimicrobial agents (for example, chloramphenicol) have less specificity and
are reserved for life-threatening infections because of the potential for serious toxicity
to the patient 13.

67. Cost of therapy :
Often several drugs may show similar efficacy in treating an infection but vary
widely in cost.
 For example, treatment of methicillin-resistant Staphylococcus aureus (MRSA)
generally includes one of the following: vancomycin, clindamycin, daptomycin, or
linezolid.
 Although choice of therapy usually centers on the site of infection, severity of the
illness, and ability to take oral medications, it is also important to consider the cost of
the medication 13.

68. Figure: Relative cost of some drugs used for the treatment of Staphylococcus aureus13.

69. DETERMINANTS OF RATIONAL DOSING:
Rational dosing of antimicrobial agents is based on their pharmacodynamic and
pharmacokinetic properties.
Three important properties that have a significant influence on the frequency of dosing
are --
 Concentration dependent killing.
 Time-dependent killing.
 Post antibiotic effect (PAE).
Utilizing these properties to optimize antibiotic dosing regimens can improve
clinical outcomes and possibly decrease the development of resistance13.

70. Concentration-dependent killing
Certain antimicrobial agents, including aminoglycosides and daptomycin, show
a significant increase in the rate of bacterial killing as the concentration of antibiotic
increases from 4- to 64-fold the MIC of the drug for the infecting organism.
 Giving drugs that exhibit this concentration-dependent killing by a once-a-day
bolus infusion achieves high peak levels, favoring rapid killing of the infecting
pathogen13.

71. Figure: Significant dose
dependent killing effect
shown by tobramycin.13

72. Time-dependent (or) Concentration-independent killing:
The clinical efficacy of some antimicrobials
is best predicted by the percentage of time that
blood concentrations of a drug remain above the
MIC13.
Figure: Non significant
dose-dependent killing
effect shown by
ticarcillin13

73. Ex: β-lactams, glycopeptides, macrolides, clindamycin, and linezolid.
 Dosing schedules for the penicillins and cephalosporins that ensure blood levels
greater than the MIC for 50% and 60% of the time, respectively, provide the most
clinical efficacy.
 Therefore, extended (generally 3 to 4 hours) or continuous (24 hours) infusions
can be utilized instead of intermittent dosing (generally 30 minutes) to achieve
prolonged time above the MIC and kill more bacteria13.

75. Postantibiotic effect (PAE):
 The PAE is a persistent suppression of microbial growth that occurs after levels
of antibiotic have fallen below the MIC.
 Antimicrobial drugs exhibiting a long PAE (for example, aminoglycosides and
fluoroquinolones) often require only one dose per day, particularly against gram
negative bacteria13.

76. CHEMOTHERAPEUTIC SPECTRA:
 Narrow-spectrum antibiotics
 Extended-spectrum antibiotics
 Broad-spectrum antibiotics

77. Narrow-spectrum antibiotics:
Chemotherapeutic agents acting only on a single or a limited group of microorganisms
are said to have a narrow spectrum. For example, isoniazid is active only against
Mycobacterium tuberculosis13.

78. Extended-spectrum antibiotics
 Extended spectrum is the term applied to antibiotics that are modified to be
effective against gram-positive organisms and also against a significant number of
gram-negative bacteria.
 For example, ampicillin is considered to have an extended spectrum because it
acts against gram-positive and some gram-negative bacteria13.

79. Broad-spectrum antibiotics:
 Drugs such as tetracycline, fluoroquinolones and carbapenems affect a wide variety
of microbial species and are referred to as broad-spectrum antibiotics.
 Administration of broad-spectrum antibiotics can drastically alter the nature of the
normal bacterial flora and precipitate a super infection due to organisms such as
Clostridium difficile, the growth of which is normally kept in check by the presence
of other colonizing microorganisms.
Ex: Tetracyclines13

80. References
1. Golan
2. Wilson and Gisvold
3. David Williams A, Thomas Lemke L. Principles of Medicinal Chemistry. 5th ed. Wolters Kluwer; 2006.
4. Karen Whalen. Illustrated reviews in Pharmacology. 6th ed. Wolters Kluwer; 2015.
5. https://explorable.com/discovery-of-bacteria
6. Brock, Thomas. Robert Koch: A life in medicine and bacteriology. ASM Press: Washington DC, 1999.
7. https://atrium.lib.uoguelph.ca/xmlui/handle/10214/6968
8. The Nobel Prize in Physiology or Medicine 1908, Paul Erlich – Biography.
9. Hugh TB (2002). "Howard Florey, Alexander Fleming and the fairy tale of penicillin". The Medical journal of
Australia 177 (1): 52–53.
10. Otten, H. (1986). "Domagk and the development of the sulphonamides". The Journal of antimicrobial
chemotherapy 17 (6): 689–696.
11. Sharma HL, Sharma KK. Principles of Pharmacology. 2nd ed. Paras medical publisher; 2013.
12. BMA dictionary.
13. Toratora