Pharmacology:
- Pharmacology is the science of the drugs system. In a wide logic, it deals
with relations of an exogenous administered chemical entity with living
systems, and any single chemical substance which can produce a natural reaction
is a ' drug'. Pharmacology includes all characteristics of facts about drugs,
but most prominently those that are pertinent to the effective and safe use of
drugs for therapeutic resolutions.
Pharmacokinetics: It means what the body does to the drug. It involves the movement of the drug.
It includes the study of absorption, distribution, metabolism and excretion of
drugs. For E.g. Paracetamol rapidly absorbed orally achieving peak blood levels
at 30 to 60 min; 25% bound to plasma proteins and consistently distributed in the
body.
Absorption: This is the process through which the drugs are
absorbed by the blood and supplied to the whole body. During absorption, the drugs
are transported into the blood or lymph by the mucous membrane.
Distribution: This is the reversible transfer of drug from one
location to another in the body. Once a drug absorbed, it gets circulated to
other body tissues that primarily had no drug. The average circulation time of
blood is just 1 minute.
Metabolism or Biotransformation: Metabolism is the chemical modification of the drug in
the body. Metabolism is divided into two types: First is Catabolism that means
the breakdown of molecules to gain energy and second is Anabolism that means
the synthesis of all compounds required by the cells.
Excretion: This
is the elimination of the systemically absorbed drug. This is the process in
which the metabolic waste of the body gets eliminated.
Pharmacodynamics: It
means what the drug does to the body. It is a quantifiable study of the biochemical,
physiological and molecular effect of the drug on the body. This comprises
physiological and biological effects of drugs, their mode of action, receptor
binding, and chemical interactions at organ system/cellular/macromolecular levels.
E.g. NSAIDs raises the COX-1-mediated inhibition of thromboxane synthesis and
therefore the risk of GI bleeding in a synergistic way.
Drug: According to the World health organization (WHO), “Drug
is any ingredient or product that is used or is projected to be used to alter
or explore physiological systems or pathological conditions for the benefit of
the receiver.” It is the single active substance existing in a medicine that is
used for diagnosis, inhibition, treatment/cure of an ailment.
Pharmacotherapeutics: It is the branch of medicine worried about the cure of
ailments or relief of symptoms and includes drug treatment. It is the
application of pharmacological info composed with information of the disease
for its anticipation, mitigation or cure. Choice of the best suitable drug,
dosage and extent of treatment considering the stage of the disease and the definite
features of a patient are a part of pharmacotherapeutics.
Clinical pharmacology: This is the scientific study of drugs (old & new)
in humans. It has a wide scope, from the discovery of new molecules to the efficacy
of drug usage in whole inhabitants. It comprises pharmacodynamic and pharmacokinetic
examination in healthy peoples as well as inpatients. The objective of clinical
pharmacology is to create information for the optimal use of drugs and the
practice of “evidence-based medicine”.
Toxicology: It
is the study of the toxic effect of drugs and other substances (household, ecological
contaminant, industrial, farming substance) with emphasis on recognition, anticipation
and treatment of poisonings. It also comprises the study of the adverse effects
of drugs.
Essential Medicines: These are the medicine that satisfies the significant
health care desires of the population. These medicines are designated with due
respect to disease occurrence and public health importance, evidence of
clinical effectiveness and safety, and relative costs and cost-effectiveness.
Orphan Drugs: These
are the drug or biological products proposed for diagnosis, prevention or
treatment of very serious diseases or illnesses that are rare. Haem arginate is
an orphan drug that is used to treat acute intermittent porphyria, variegate
porphyria and hereditary coproporphyria.
Bioavailability: This is the rate and extent of absorption active
moiety (drug or metabolite) from dosage form administered by any route of
administration, enters in the systemic circulation, thus retrieving the site of
action. The bioavailability of a drug is mainly determined by the characteristics
of the dosage form, which partially depend on its design and production.
It is a degree of the fraction (F) of the administered
dose of a drug that spreads the systemic circulation in the unchanged form. The
bioavailability of drug injected IV is 100% but is normally lower after oral administration.
Receptor: This is a macromolecule or protein or binding site positioned
on the surface or inside the target cell that supports identifying the signal
molecule and start the response to it, but it has no other function.
Affinity:
The capability to bind with the
receptor is known as affinity. The affinity of a drug for a receptor governs its
concertation nearby the receptor necessary to form a definite number of
drug-receptor relations.
Intrinsic activity: Intrinsic
activity of a drug is the extent of its capability to induce a functional alteration
in the receptor that could vary from 0 to 1 (nil to maximal).
Agonist: A drug that stimulates a receptor to produce an effect
alike to that of the physiological signal molecule. Agonists have both,
affinity and utmost intrinsic activity (IA=1). E.g. morphine, adrenaline etc.
Inverse agonist: A drug that triggers a receptor to produce an effect
in the opposite way to that of the agonist. This produces an effect that is
pharmacologically opposite to agonist. It has affinity but intrinsic activity
with a minus sign. (IA= 0 to -1).
Partial agonist: A drug that activates a receptor to produce a fractional
effect but provokes the action of a full agonist. This does not produce a maximal
effect even when the concentration of the drug is increased. This has an affinity
and submaximal intrinsic activity (IA= 0 to 1). E.g. Busprione on the 5-HT
receptor. Partial agonists also antagonize the effects of a full agonist, as
they conquer a large quantity of the receptors.
Full agonist: This is a drug that is capable of producing the
maximum response as it shows full effectiveness at the receptor.
Antagonist: A drug that prevents the action of an agonist on a
receptor or the successive response, but does not have any effect of its own.
It does not produce any biological response. It may be competitive or
non-competitive.
Competitive antagonists: This binds selectively to the active site of the
receptor without causing activation, averting the agonist from binding and producing
its effect. Competitive antagonists bind
to the receptor but do not stimulate it, while some drugs are partial agonists
which conquer and submaximally stimulate the receptor. They have affinity but
no intrinsic activity (IA=0). E.g. Propranolol, Atropine etc.
Non-competitive antagonists: This may affect the response by irreversibly binding
to the active site of the receptor or an allosteric site, so this does not compete
with the agonist.
Drug action: It is the preliminary arrangement of the drug with its
receptor causing the conformational alteration in the end (in case of
agonists), or prevention of conformational alteration through the elimination
of the agonist (in case of antagonists).
Drug effect: A drug can attain the desired effect. It is the final
change in biological role brought about as a sign of drug action.
Drug potency: Potency is the amount of drug needed to produce a
certain response. Relative potency is more
significant than absolute potency and is well-defined by relating the dose of
the two agonists at which they produce a half-maximal response (EC50).
Drug efficacy: It is the best response that can be produced by the
drug, e.g. morphine produces a degree of analgesia that is not attainable at
any dose of aspirin. Efficacy is a more significant factor in the selection of
a drug.
Synergism: When the action of one drug is expedited or improved
by the other drug, they are assumed to be synergistic. In a synergistic pair.
both the drugs may have the action in the same way. When given alone, one drug
may be inactive but still increase the action of the other drug when given
together.
Antagonism: When one drug declines or stops the action of another
drug, it is known as antagonistic. In
an antagonistic pair, one drug is inactive but declines the effect of the
other.
Placebo: An inert substance, that is given in the attire of a
medicine. It works by psychodynamic instead of pharmacodynamic means and regularly
produces response corresponding to the active drug.
Evidence-based medicine: This is the process of systematic discovery,
appraising and using modern research discoveries as the basis of clinical
results.
Adverse effect: Any unwanted or unintended importance of drug
administration. It contains all kinds of toxic effect- trivial, serious or even
lethal.
Adverse drug reaction (ADR): Any harmful alteration which is supposed to be due to
a drug, arises at doses usually used in man, needs treatment or decrease in
dose or specifies attention in the future use of the similar drug.
Pharmacovigilance: Pharmacovigilance is also called drug safety. It is the
science and actions related to the recognition, assessment, monitoring and
prevention of adverse effect or any other drug-related complications.
Side effects: It is undesirable but often unavoidable,
pharmacodynamic effects that arise at the therapeutic dose. A side effect may
be based on a similar action as the therapeutic effect, e.g. atropine is used
in pre-anaesthetic medicine for its anti-secretory effects.
Toxic effects: This is the extreme pharmacological action of the drug
due to overdosage or extended use of the drug. Overdosage may be absolute
(accidental, destructive, suicidal) or comparative. The CNS, CVS, Liver, Kidney,
Lung, Skin and Blood forming organs are most frequently complicated in drug toxicity.
Intolerance: It is the opposite of tolerance and shows a low
threshold of the individual to the drug action.
Idiosyncrasy: This is the unusual feature of the person. It refers
to genetically determined atypical reactivity to a chemical.
Drug allergy: It is an immunologically facilitated reaction producing
stereotype indications that are dissimilar to the pharmacodynamic effect of the
drug.
Drug dependence: It is a transformed biological state produced by
recurrent administration of a drug that requires the sustained existence of the
drug to keep physiological symmetry. Termination of the drug results in a distinctive
withdrawal (abstinence) syndrome.
Teratogenicity: It mentions the capacity of a drug to cause foetal
irregularities when administered to the pregnant mother. The placenta does not
establish a stringent barrier, and any drug can cross it to a superior or
smaller level.
Mutagenicity: It is the capability of a drug to cause genetic deficiencies.
Typically, oxidation of the drug causes the creation of reactive intermediates
which affect genes and may cause essential changes in the genetic materials.
Drug-induced diseases: These is also known as iatrogenic (physician induced)
diseases and are functional disorders (disease) triggered by drugs that persist
even after the aberrant drug has been inhibited and mainly excluded.
Therapeutic index: This is also known as the safety margin. This is
defined as a gap between the therapeutic effect DRC and the adverse effect DRC
of the drug.
LD50: This is the median lethal dose (LD50). It
is the drug concentration that kills half (50%)of the receivers.
ED50: This is the median effective dose (ED50).
This is the concentration of drug which produces the quantified effect in 50%
individual.
EC50: The concentration of a drug (two agonists) that
provides a half-maximal response (EC50).
First-pass (Pre-systemic) Metabolism:
This is the metabolism of a drug
through its passage from the absorption site into the systemic circulation.
During the first-pass metabolism, the concentration of the drug (when
administered through oral route), is greatly reduced before it reaches the
systemic circulation.
Clearance (CL): The clearance of a drug is the hypothetical volume of
blood plasma from which the drug is totally removed in unit time.
CL=Rate of elimination/C
Plasma half-life: It is the time occupied for its blood plasma concentration to be reduced to half of its novel value. This is denoted as. t 1⁄2
Loading dose: This is a distinct or rapidly repeated dose given at
the start to accomplish target concentration quickly.
Maintenance dose: This is the dose that is to be repeated at definite breaks
after the accomplishment of target CPSS to keep the same by balancing excretion.
Bioequivalence: Oral preparations of a drug from diverse manufacturers
or dissimilar batches from the same manufacturer may have the same quantity of
the drug (chemically equivalent) but may not yield the same blood levels
biologically inequivalent. when the bioavailability of the active drug from
them is not considerably different under appropriate test situations, measured
bioequivalent.
In-Vivo: This refers to experimentation with or within a whole
living organism.
In-Vitro: These are the studies
performed using components of an organism that have been obtained from their typical
biological environments.
Ex- Vivo: This is the experimentation using biological tissue in
an artificial atmosphere outside the living organism. It may contain a short-term
(up to 24 hours) culture of tissue, after its exclusion from the organism.
In-situ: This is experiments in a lab situation emphasis on a definite
protein or gene, considering it inside an entire organism. It is the Latin term
for “on-site” or “in position”.
In-silico: The experimentation that is performed that is
performed on computer or via computer simulation.
References: -
- Essentials of Medical Pharmacology, Eighth Edition, KD Triphathi, Jaypee Brothers Medical Publishers (P) Ltd, 2019.
- Pharmacology term guide
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