Pharmacology & Drug Classifications
Pharmacology
Pharmacology (in Greek: pharmacon meaning drug, and logos meaning science) is the study of how chemical substances interact with living systems. If substances have medicinal properties, they are considered pharmaceuticals. The field encompasses drug composition and properties, interactions, toxicology, therapy, and medical applications and antipathogenic capabilities. The science is considered to have been invented by Arab physicians in Baghdad during the Golden Age of Islam; pharmacopoeias were penned in Arabic as early as the 7th century.
Pharmacology as a science is practiced by pharmacologists. Subdisciplines are clinical pharmacology (the medical field of medication effects on humans), neuro- and psychopharmacology (effects of medication on behavior and nervous system functioning), and theoretical pharmacology.
Drug
A drug is any chemical substance, other than a food or device, that affects the function of living things. Technically, vitamin E, oxygen, and cocaine are all examples of drugs. Various drugs can be used to treat illness, or they can be used recreationally to alter behavior and perception.
Drugs used as medicines
A medication is a licensed drug taken to cure or reduce symptoms of an illness or medical condition. Medications are generally divided into two groups -- over the counter (OTC) medications, which are available in pharmacies and supermarkets without special restrictions, and Prescription only medicines (POM), which must be prescribed by a physician. Most OTC medication is generally considered to be safe enough that most persons will not hurt themselves accidentally by taking it as instructed. Many countries, such as the UK have a third category of pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist. However, the precise distinction between OTC and prescription depends on the legal jurisdiction. Medications are typically produced by pharmaceutical companies and are often patented. Those that are not patented are called generic drugs.
Classification based on System response
Medication can be usually classified in various ways, e.g. by its chemical properties, mode of administration, or biological system affected. An elaborate and widely used classification system is the Anatomical Therapeutic Chemical Classification System.
Types Of Medication
For the gastrointestinal tract or digestive system
§ Upper digestive tract: antacids, reflux suppressants, antiflatulents, antidopaminergics, proton pump inhibitors, H2-receptor antagonists, cytoprotectants, prostaglandin analogues
§ Lower digestive tract: laxatives, antispasmodics, antidiarrhoeals, bile acid sequestrants, opioids
For the cardiovascular system
§ General: beta-receptor blocker, calcium channel blockers, diuretics, cardiac glycosides, antiarrhythmics, nitrate, Antianginals, vasoconstrictor, vasodilator, peripheral activator
§ Affecting Blood pressure: ACE inhibitors, angiotensin receptor blockers, alpha blocker
§ Coagulation: anticoagulant, heparin, antiplatelet drug, fibrinolytic, anti-hemophilic factor, hemostatic drugs
§ Atherosclerosis/cholesterol agents: hypolipidemic agents, statins.
For the central nervous system
Hypnotic, anesthetics, antipsychotic, antidepressant (including tricyclic antidepressants, monoamine oxidase inhibitor, lithium salt, selective serotonin reuptake inhibitor), anti-emetic, anticonvulsant and antiepileptic, anxiolytic, barbiturate, movement disorder drug, stimulant (including amphetamines), benzodiazepine, cyclopyrrolone, dopamine antagonist, antihistamine, cholinergic, anticholinergic, emetic, cannabinoids, 5-HT antagonist.
For pain & consciousness (Analgesic drugs)
The main classes of painkillers are NSAIDs, opioids and various orphans such as paracetamol, tricyclic antidepressants and anticonvulsants.
For musculoskeletal disorders
NSAIDs (including COX-2 selective inhibitors), muscle relaxant, neuromuscular drug
anticholinesterase
For the eye
§ General: adrenergic neurone blocker, astringent, ocular lubricant
§ Diagnostic: topical anesthetics, sympathomimetics, parasympatholytics, mydriatics, cycloplegics
§ Anti-bacterial: antibiotics, topical antibiotics, sulfa drugs, aminoglycosides, fluoroquinolones
§ Anti-viral:
§ Anti-fungal: imidazoles, polyenes
§ Anti-inflammatory: NSAIDs, corticosteroids
§ Anti-allergy: mast cell inhibitors
§ Anti-glaucoma: adrenergic agonists, beta-blockers, carbonic anhydrase inhibitors/hyperosmotics, cholinergics, miotics, parasympathomimetics, prostaglandin agonists/prostaglandin inhibitors. nitroglycerin
For the ear, nose and oropharynx
Sympathomimetic, antihistamine, anticholinergic, NSAIDs, steroid, antiseptic, local anesthetic, antifungal, ceruminolytic
For the respiratory system
§ bronchodilator, NSAIDs, anti-allergic, antitussive, mucolytic, decongestant
§ corticosteroid, beta-receptor antagonist, anticholinergic, steroid
For endocrine problems
androgen, antiandrogen, gonadotropin, corticosteroid, growth hormone, insulin, antidiabetic (sulfonylurea, biguanide/metformin, thiazolidinedione, insulin), thyroid hormones, antithyroid drugs, calcitonin, diphosphonate, vasopressin analogues
For the reproductive system or urinary system
antifungal, alkalising agent, quinolones, antibiotic, cholinergic, anticholinergic, anticholinesterase, antispasmodic, 5-alpha reductase inhibitor, selective alpha-1 blocker, sildenafil
For contraception
contraceptive, oral contraceptives, spermicide, depot contraceptives
For obstetrics and gynecology
NSAIDs, anticholinergic, hemostatic drug, antifibrinolytic, Hormone Replacement Therapy, bone regulator, beta-receptor agonist, follicle stimulating hormone, luteinizing hormone, LHRH
gamolenic acid, gonadotropin release inhibitor, progestogen, dopamine agonist, oestrogen, prostaglandin, gonadorelin, clomiphene, tamoxifen, Diethylstilbestrol
For the skin
emollient, anti-pruritic, antifungal, disinfectant, scabicide, pediculicide, tar products, vitamin A derivatives, vitamin D analogue, keratolytic, abrasive, systemic antibiotic, topical antibiotic, hormones, desloughing agent, exudate absorbent, fibrinolytic, proteolytic, sunscreen, antiperspirant, corticosteroid
For infections and infestations
antibiotic, antifungal, antileprotic, antituberculous drug, antimalarial, anthelmintic, amoebicide, antiviral, antiprotozoal, antiserum
For immunology
vaccine, immunoglobulin, immunosuppressant, interferon, monoclonal antibody
For allergic disorders
anti-allergic, antihistamine, NSAIDs
For nutrition
tonic, iron preparation, electrolyte, parenteral nutritional supplement, vitamins, anti-obesity drug, anabolic drug, hematopoietic drug, food product drug
For neoplastic disorders
cytotoxic drug, sex hormones, aromatase inhibitor, somatostatin inhibitor, recombinant interleukins, G-CSF, erythropoietin
For diagnostics
Contrast media
Placebo
The technical term placebo is precisely applied in the specialized medical domains of pharmacology, nosology, and aetiology to denote the pharmacologically inert, dummy simulator of an "active" drug that serves as a scientific control in clinical trials designed to determine the clinical efficacy of that particular drug
In particular, these clinical trials are conducted in order to determine whether a drug's supposedly active ingredients affect the subject through direct physiochemical processes or through mind-mediation.
Generic drug
Generic drug (pl. generic drugs, short: generics) is a drug which is bioequivalent to a brand name drug with respect to pharmacokinetic and pharmacodynamic properties, but is normally sold for a lower price. Generic medicines must contain the same active ingredient at the same strength as the "innovator" brand, be bioequivalent, and are required to meet the same pharmacopeial requirements for the preparation. By extension, therefore, generics are assumed to be identical in dose, strength, route of administration, safety, efficacy, and intended use.
The principal reason for the reduced cost of generic medicines is that these are manufactured by smaller pharmaceutical companies which do not invest in research and development into new drugs or massive television and radio advertising campaigns. Generic manufacturers also do not give away thousands of doses of their drugs for 'promotional purposes'.
Route Of Administration
In pharmacology and toxicology, a route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body.
Obviously, a substance must be transported from the site of entry to the part of the body where its action is desired to take place (even if this only means penetration through the stratum corneum into the skin). However, using the body's transport mechanisms for this purpose can be far from trivial. The pharmacokinetic properties of a drug (that is, those related to processes of uptake, distribution, and elimination) are critically influenced by the route of administration.
Classification
Routes of administration can broadly be divided into:
§ topical: local effect, substance is applied directly where its action is desired
§ enteral: desired effect is systemic (non-local), substance is given via the digestive tract
§ parenteral: desired effect is systemic, substance is given by other routes than the digestive tract
The U.S. Food and Drug Administration recognizes 111 distinct routes of administration.
The following is a brief list of some routes of administration.
Topical
§ epicutaneous (application onto the skin), e.g. allergy testing, topical local anesthesia
§ inhalational, e.g. asthma medications
§ enema, e.g. contrast media for imaging of the bowel
§ eye drops (onto the conjunctiva), e.g. antibiotics for conjunctivitis
§ ear drops - such as antibiotics and corticosteroids for otitis externa
§ intranasal, e.g. decongestant nasal sprays
Enteral
§ by mouth (orally), many drugs as tablets, capsules, or drops
§ by gastric feeding tube, duodenal feeding tube, or gastrostomy, many drugs and enteral nutrition
§ rectally, various drugs in suppository or enema form
Parenteral by injection or infusion
§ intravenous (into a vein), e.g. many drugs, total parenteral nutrition
§ intraarterial (into an artery), e.g. vasodilator drugs in the treatment of vasospasm and thrombolytic drugs for treatment of embolism
§ intramuscular (into a muscle), e.g. many vaccines, antibiotics, and long-term psychoactive agents.
§ intracardiac (into the heart), e.g. adrenaline during cardiopulmonary resuscitation (not commonly performed anymore)
§ subcutaneous (under the skin), e.g. insulin
§ intraosseous infusion (into the bone marrow) is, in effect, an indirect intravenous access because the bone marrow drains directly into the venous system. This route is occasionally used for drugs and fluids in emergency medicine and pediatrics when intravenous access is difficult
§ intradermal, (into the skin itself) is used for skin testing some allergens, and also for tattoos
§ intraperitoneal, (into the peritoneum) is predominantly used in veterinary medicine and animal testing for the administration of systemic drugs and fluids due to the ease of administration compared with other parenteral methods.
Parenteral (other than oral)
§ transdermal (diffusion through the intact skin), e.g. transdermal opioid patches in pain therapy
§ transmucosal (diffusion through a mucous membrane), e.g. cocaine snorting, sublingual nitroglycerine
§ inhalational, e.g. inhalational anesthetics
Other
§ intraperitoneal (infusion or injection into the peritoneal cavity), e.g. peritoneal dialysis
§ epidural (synonym: peridural) (injection or infusion into the epidural space), e.g. epidural anesthesia
§ intrathecal (injection or infusion into the cerebrospinal fluid), e.g. antibiotics, spinal anesthesia
§ intravitreal - is a route of administration of a drug, or other substance, in which the substance is delivered via an eye. "Intravitreal" literally means "inside an eye".
Pharmaceutical Forms
Pharmaceutical form is the way the drugs are delivered to the patient.
Types of pharmaceutical forms (abbreviation, latin origin)
§ ampule (amp; lat. ampula)
§ capsule (cap., caps.; lat. capsula)
§ cream (cr., crm.)
§ elixir (elix.)
§ emulsion (emuls.; lat. emulsum)
§ fluid (fl., fld.; lat. fluidum)
§ grain (gr.)
§ drop(s) (gtt(s).; lat. gutta(e))
§ injection (inj.; lat. injectio)
§ solution (liq.; lat. liquor)
§ solution (sol.; lat. solutio)
§ lotion (lot.; lat. lotio)
§ a spray (nebul.; lat. nebula)
§ powder (pulv.; lat. pulvis)
§ suspension (susp.; lat. suspensio)
§ syrup (syr.; lat. syrupus)
§ tablet (tab.; lat. tabella)
§ tincture (tr., tinc., tinct.; lat. tinctura)
§ ointment (ung.; lat. unguentum)
Injection
An injection is a method of putting liquid into the body with a hollow needle and a syringe, which is pierced through the skin long enough for the material to be forced into the body. An injection follows a parenteral route of administration, that is, its effect is not necessarily local to the area in which the injection is administered; it is systematic.
There are generally three types of injections-subcutaneous injections, intramuscular injections, and intravenous infusions.
Subcutaneous Injection
A subcutaneous injection is administered into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the cutis. Subcutaneous injections are highly effective in administering such medications as insulin or goserelin.
A person with Type I diabetes mellitus typically injects insulin subcutaneously. Places on the body where people can inject insulin most easily are:
§ The outer area of the upper arm.
§ Just above and below the waist, except the area right around the navel (a 2-inch circle).
§ The upper area of the buttock, just behind the hip bone.
§ The front of the thigh, midway to the outer side, 4 inches below the top of the thigh to 4 inches above the knee.
These areas can vary with the size of the person. Changing the injection site keeps lumps or small dents called lipodystrophies from forming in the skin. However, people should try to use the same body area for injections that are given at the same time each day-for example, always using the stomach for the morning injection or an arm for the evening injection[citation needed]. Using the same body area for these routine injections lessens the possibility of changes in the timing and action of insulin.[citation needed]
Intramuscular Injection
An intramuscular injection is a substance injected directly into a muscle. Many vaccines are administered intramuscularly, as well as codeine, metoclopramide, and many other medications. Many drugs injected intramuscularly are absorbed into the muscle fairly quickly, while others are more gradual.
Generally, intramuscular injections are not self-administered, but rather by a trained medical professional. However, prescribed self-administered intramuscular injections are perhaps becoming more common with time for patients that require these injections on a routine basis.
Intravenous Infusion
An intravenous infusion is a liquid administered directly into the bloodstream via a vein. The first polio vaccine in 1952 was injected intravenously until an oral vaccine replaced it in 1955.
There are other types of injections too like
§ Intracardiac injection
§ Intradermal injection
§ Intraosseous infusion
§ Intraarterial injection
Drug Action
The action of drugs on the human body is called pharmacodynamics, and what the body does with the drug is called pharmacokinetics. The drugs that enter the human tend to stimulate certain receptors, ion channels, act on enzymes or transporter proteins. As a result, they cause the human body to reaction in a specific way.
There are two different types of drugs:
§ Agonists - they stimulate and activate the receptors
§ Antagonists - they stop the agonists from stimulating the receptors
Once the receptors are activated, they either trigger a particular response directly on the body, or they trigger the release of hormones and/or other endogenous drugs in the body to stimulate a particular response.
Adverse drug reaction/Drug toxicity
An adverse drug reaction (abbreviated ADR) is a term to describe the unwanted, negative consequences sometimes associated with the use of medications. ADR is a particular type of adverse effect. The term is preferred over the colloquial and imprecise "side effect", as the term "side effect" implies the potential for beneficial consequences and that the effects are not explained by the pharmacological actions of the drug.
While ADR is probably the most precise term to describe the concept, it is not widely used in the community since it may be perceived as jargon and because of the negative-associations with the term "drug". Alternative terms with equivalent meaning to ADR include: side effect, adverse event, adverse effect, etc.
There are many types of ADRs:
§ Type A, pharmacologically predictable
§ Type B, bizarre and unpredictable
§ Type C, arising from chronic use
§ Type D, delayed reaction
§ Type E, end of dose reaction
§ Type F, Failure of therapy
Iatrogenesis
Iatrogenesis literally means "brought forth by a healer" (iatros means healer in Greek); as such, it can refer to good or bad effects, but it is almost exclusively used to refer to the causation of a state of ill health or adverse effect or complication caused by or resulting from medical treatment.
There are many sources of iatrogenesis:
§ physician error
§ prescription drug interaction
§ adverse effects of prescription drugs
§ unproven or radical treatments
§ biased diagnosis
§ nosocomial infection
§ medical torture
§ unethical medical experimentation
Contraindication
In medicine, a contraindication is a condition or factor that increases the risk involved in using a particular drug, carrying out a medical procedure or engaging in a particular activity.
§ An absolute contraindication is a condition that prohibits the use of a treatment altogether. For example, an untreated pneumothorax would be an absolute contraindication to hyperbaric oxygen therapy.
§ A relative contraindication weighs in against the use of a treatment when assessing its risk/benefit ratio.
Drug Dosing Terminology
These are some of the most commonly used drug abbreviations:
a.c. before meals or food
b.i.d. twice daily
h.s. at bedtime
p.c. after meals
p.o. by mouth
p.r.n. as needed
O.D. right eye
O.S. left eye
O.U. each eye
mcg microgram(s)
mg milligram(s)
mEq milliequivalent(s)
ML milliliter(s)
q.o.d. every other day
q.h. every hour
q.4h. every four hours
q.8h. every eight hours
q.i.d. four times a day
q.o.d. every other day
t.i.d. three times a day
Some Dos and Donts in drug prescription:
Don’t Dos
q.day q.d.
q. four hours q.4h.
.80 mg 0.80 mg
five hundred mg 500 mg
DRUG CLASSIFICATION
Acne Vulgaris Drugs
These drugs control the inflammatory eruptions composed of cysts, papules, and comedones, predominantly on the face, upper back, and chest. The condition occurs in a majority of people during puberty and adolescence. Examples: Benzoyl peroxide, tretinoin, Ultra, Olux, and topical erythromycin.
Anabolic Agents
Anabolic agents are the ones, which can stimulate growth of muscle mass. They are the compounds with androgenic properties and are used in severe cases of emaciation and most prominently by athletes to increase their muscle size, strength, and endurance. Some of the examples are Histerone 100, Depo-Testosterone, Malogen, etc.
Analgesics
Analgesics or as the name suggests are drugs, which have the property of reducing the pain or rather producing a neurologic and pharmacologic state in which the painful stimuli are blunted so much so that though they are still perceived, they are no longer painful.
Antacid
Antacids are agents used to neutralize the excess acid in the stomach released in cases of acidity, gastritis and ulcers. They neutralize the effects of HCl, thereby providing relief from indigestion and heartburn. The efficacy of antacids depends on their capacity to protect the mucosa of the stomach from acid and pepsin. Drugs: Calcium carbonate.
Antiallergics
Antiallergics prevent, inhibit, and alleviate allergic reactions. Generally, histamines are responsible for allergies. Antiallergics act as antihistamines and suppress their effects. Antiallergics act against itching and flash responses of the histamines. Antihistamines are subdivided in two broad categories: sedative and non-sedative. Cetirizine is one example of non-sedative antihistamine, while diphenhydramine and hydroxyzine are the examples of sedative antihistamines. Two lesser known categories of antihistamines are mast cell stabilizers and histamine receptor blockers.
Antianginals
Antianginals act against angina pectoris, that is the symptom exhibited in ischemic heart disease. Antianginals improve the balance between the delivery of oxygen to myocardium and its utilization by the myocardium. Antianginals are available in various forms, viz., calcium channel blockers, organic nitrates, beta-adrenergic blockers, potassium channel activators, and antiplatelet drugs. These drugs relieve angina pectoris by expanding blood vessels of the heart. Some are nitroglycerin, nifedipine, diltiazem, and verapamil.
Antiarrhythmics
Antiarrhythmic drugs are used to treat irregular heart rhythms resulting from the disturbance in the heart's electrical firing system. Antiarrhythmic drugs enhance the blood flow in the coronary vessels of the heart. This causes vasodilation and decreases the resistance felt in the peripheral vascular system. Clinically, antiarrhythmics are divided into three broad categories;
a) Which act on supraventricular arrhythmia (like digoxin and verapamil).
b) Which act on both supraventricular and ventricular arrhythmia (quinidine, amiodarone, metoprolol)
c) Which act solely on the ventricular arrhythmia.
Anticoagulants
Anticoagulants delay the clotting or coagulation process of blood. When any vessel is blocked by a clot of blood, an anticoagulant is administered to prevent new clots from forming with the earlier clots and thereby suppressing their enlargement. However, an anticoagulant only prevents from blood clotting but is incapable of dissolving an existing blood clot. Patients with artificial heart valves and atrial fibrillation are at the risk of forming blood clots and they are therefore prescribed anticoagulants to prevent such a situation. Heparin and warfarin are the most commonly used anticoagulants.
Anticonvulsants
Anticonvulsants alleviate or reduce the severity of seizures and also prevent further seizure attacks.
Antidepressants
Drugs useful in treatment of depression are termed as anti-depressants. There are three kinds of antidepressants, viz., tetracyclic, triazolopyridine, and tricyclic.
Antidiabetics
Antidiabetic agents are drugs that lower the blood sugar level. They are therefore also called hypoglycemic drugs. They are of two types; sulfonylureas and biguanides. Examples of sulfonylureas are chlorpropamide and glipizide while Metformin and phenformin are biguanides.
Antidiarrheals
Antidiarrheals are the agents used to relieve diarrhea. They do so either by absorbing the excess fluids that cause diarrhea or by slowing the movement of fecal material through intestine thereby allowing more time for absorption of water. The first step in treatment of diarrhea is replacement of fluid and electrolytes.
Antiemetics