PHARMACY AND PHARMACOLOGY DRUG

Dispensing Technique-II: Comprehensive Questions and Answers

This document provides a detailed Q&A compilation derived from "Dispensing Technique-II" textbook pages. All main headings, subheadings, and their associated content have been meticulously extracted and formatted into a blog-style structure.

PHARMACY AND PHARMACOLOGY

DRUG

Question: How is a drug defined?

Answer: A drug may be defined as any substance that is used to diagnose, prevent or treat a disease.

THE NATURE OF DRUGS

Question: What are the common uses/types of substances classified as drugs?

Answer: Drugs in common use include: Inorganic ions, Non peptide organic molecules, Small peptides and proteins, Nucleic acids, Lipids, Carbohydrates.

Question: What are the origins of drugs?

Answer: Some drugs are found in plants or animals, while others are partially or completely synthetic.

A. Size and Molecular Weight

Question: How do drugs vary in size and molecular weight?

Answer: Drugs vary in size from molecular weight (MW) 7 (e.g., Lithium) to over MW 50,000 (e.g., Thrombolytic enzymes, antibodies, other proteins). Most drugs, however, have MWs between 100 and 1000.

B. Drug-Receptor Proteins

Question: What are drug receptors?

Answer: Drug receptors are the molecular components of the body with which drugs interact to bring about their effects.

Question: What types of chemical bonds are involved in drug-receptor interactions?

Answer: Drugs bind to receptors with a variety of chemical bonds. These include: very strong covalent bonds (which usually result in irreversible action), somewhat weaker electrostatic bonds (e.g., between a cation and an anion), and much weaker interactions (e.g., hydrogen, van der Waals, and hydrophobic bonds).

Question: What is an Agonist?

Answer: If drug-receptor binding results in activation of the receptor, the drug is termed an agonist.

Question: What is an Antagonist?

Answer: If inhibition results from drug-receptor binding, the drug is considered an antagonist.

NOMENCLATURE OF DRUGS

Question: How many names can a drug typically have?

Answer: A drug may have more than one name. Actually, most drugs have at least three names.

Question: What is a Chemical Name for a drug?

Answer: This indicates the molecular structure. Many of these names are complex and describe the compound for chemists.

Question: What is an Official (Approved) Name for a drug?

Answer: It is usually the abbreviated form of the chemical name. This name is used in pharmacopoeia and chosen by official bodies.

Question: What is a Proprietary Name (Brand, Trade Name) for a drug?

Answer: This is the name given by the company which markets the drug. It is the commercial property of a pharmaceutical company and indicates a particular formulation of a substance by a specific manufacturer.

Question: Why can drug names cause confusion?

Answer: Since several companies market the same drug under different proprietary names, unnecessary confusion may arise. Therefore, whenever possible, drugs should be prescribed by their approved names.

Question: Provide an example of a drug's different names.

Answer: Example: Chemical Name: Acetyl-p-aminophenol; Official Name: Paracetamol; Proprietary Name: Calpol, Panadol.

SOURCES OF DRUGS

Question: What are Vegetable Sources (Plant Source) of drugs?

Answer: This is the oldest source of drugs. All parts of plants are used as drugs, such as leaves, seeds, flowers, roots, and bark.

Question: Give examples of drugs and their active principles derived from vegetable sources.

Answer: Examples: Belladonna leaves, Belladonna root, Cinchona bark, Digitalis leaves, Nux vomica seeds, Senna leaves, Senna fruit. The action of crude drugs is due to Active Principles contained in them, e.g., Belladonna contains atropine, opium contains morphine, cinchona contains quinine, digitalis contains digoxin.

ii. Animal Sources:

Question: What are Animal Sources of drugs?

Answer: Various organs and tissues of animals were used in the past without understanding their mechanism of action. Active principles of animal drugs are Proteins, Oil and fats, Enzymes and Hormones. At present, Insulin and Sex Hormones are obtained from animal sources.

iii. Mineral Sources:

Question: What are Mineral Sources of drugs?

Answer: Metals, metalloids, non-metal substances and their compounds have been used as drugs. Mercury was one of the earliest drugs to be used for the treatment of syphilis. At present, iron is used for the treatment of anemia, iodine for thyroid problems, and as an antiseptic.

iv. Synthetic Sources:

Question: What are Synthetic Sources of drugs?

Answer: These days, drugs are prepared in pharmaceutical laboratories. They may be organic or inorganic, or a combination of organic and inorganic compounds. Chloroform, ether, nitrous oxide, and chloral hydrate were the earliest synthetic drugs. Later, derivatives of active principles of crude drugs were prepared along with advancement in the knowledge of chemistry. At present, more than 90% of drugs used for patient treatment are prepared synthetically. Antipyretics, sulphonamides, antihistamines, anticonvulsants, and antianxiety agents are examples of such drugs.

v. Microbiological Sources:

Question: What are Microbiological Sources of drugs?

Answer: Antibiotic drugs, which are very useful for treating infections, have been prepared from bacteria and fungi. Penicillium was the first antibiotic to be discovered. Some vitamins have also been prepared from such sources.

Following are the active principles of crude drugs

Question: What are Alkaloids?

Answer: These are active nitrogenous compounds, alkaline in nature, and intensely bitter. Most are insoluble in water and are solids (e.g., Belladonna contains atropine and hyoscine; Opium contains morphine).

Question: What are Glycosides?

Answer: These are highly active and complex substances containing carbon, hydrogen, and oxygen. They undergo hydrolysis by either acid or enzymes in the presence of water, leading to the formation of sugar and non-sugar components. The non-sugar component, known as aglycone or genin, possesses pharmacological activity. Examples include digoxin, digitoxin, gitoxin, and gitalin.

iii. Emulsions:

Question: What are Emulsions?

Answer: They act as emulsifying agents as they are both water and fat soluble (e.g., glycyrrhizin).

iv. Fixed oils:

Question: What are Fixed oils?

Answer: These are oils obtained from plants and animals. They are called fixed oils because they can't be distilled without being decomposed. They form soaps with alkalies (e.g., castor oil, olive oil).

v. Volatile oils:

Question: What are Volatile oils?

Answer: They are obtained from parts of plants like flowers, fruit, and leaves. They are highly aromatic and slightly soluble in water. They contain liquid hydrocarbons or some contain oxidized hydrocarbons (e.g., menthol, thymol, camphor).

vi. Fats:

Question: What are Fats?

Answer: A fat is a fixed oil which is solid at room temperature. These are natural esters of glycerol and fatty acids. All three OH groups of glycerol are esterified in fats; therefore, they are known as triglycerides.

vii. Waxes:

Question: What are Waxes?

Answer: These are esters of fatty acids with monohydric alcohol. They are used in the preparation of ointments and other drugs used locally on skins (e.g., beeswax).

viii. Gums:

Question: What are Gums?

Answer: They are exudation of plants and contain carbohydrates. They form a viscous solution with water known as mucilage. Gums and mucilage are used for the preparation of suspension and emulsion.

ix. Resins:

Question: What are Resins?

Answer: They form resin soaps with alkalies which are used in the preparation of emulsions and pills.

x. Oleoresins:

Question: What are Oleoresins?

Answer: They are formed when resins are dissolved in volatile oils.

xi. Gum resin:

Question: What is Gum resin?

Answer: They are a combination of gum and resin. Used in dentistry.

xii. Balsams:

Question: What are Balsams?

Answer: These are a combination of resin with benzoic acid or cinnamic acid or both. Benzoin is applied on small superficial wounds and abrasions.

xiii. Tannins:

Question: What are Tannins?

Answer: These are non-nitrogenous compounds possessing astringent action on mucous membrane. Some are hydrolyzed to tannic acid. They are precipitated by metallic salts and alkaloids.

xiv. Neutral principles:

Question: What are Neutral principles?

Answer: These are active substances which do not belong to any special group (e.g., Santonin).

Additional Information (Page 11 - Predominantly Urdu/Farsi)

Page 11 contains general textbook elements in Urdu/Farsi, likely a continuation of drug classifications or properties, but without explicit English headings or content for Q&A generation. The content appears to be a list of classifications or characteristics, but the specific details are not extractable in English from the provided image.

DOSAGE FORMS

Question: What are dosage forms?

Answer: Dosage forms are pharmaceutical products that typically involve combinations of active drug components and inert components. In addition, excipients are used to solubilize, color, flavor, and fashion medicinal agents into effective and appealing dosage forms.

Question: How are dosage forms classified?

Answer: Dosage forms can be classified according to: 1) Physical forms; 2) Route of administration.

A. SOLID DOSAGE FORMS

Question: List the common types of solid dosage forms.

Answer: The common types are: 1. Powders; 2. Granules; 3. Tablets; 4. Capsules; 5. Modified Release dosage forms.

Question: What are Powders?

Answer: These are drugs or drug extracts that are dried, ground and converted into fine particles. They can be used orally, by dusting or as insufflations.

Question: What are Oral powders?

Answer: They are intended to be suspended or dissolved in water or mixed with foods (e.g., antacids and laxatives).

Question: What are Dusting powders?

Answer: Dusting powders are meant for external application, typically to the skin.

2. GRANULES:

Question: What are Granules in pharmaceutics?

Answer: They consist of solid drug aggregates of powder particles, often supplied in single-dose sachets. Some granules are placed on the tongue and swallowed with water, while others are intended to be dissolved in water before taking.

3. TABLETS:

Question: What are Tablets?

Answer: It is a form of drug in which active forms are modulated or compressed into different shapes and sizes. Binding closures and polymer coatings may be applied to improve palatability, make them smoother & easier to swallow, more resistant to the environment, and extend shelf life. Tablets are often administered through oral, buccal, sublingual, or rectal routes. Sublingual routes involve chewing tablets for rapid drug release into the bloodstream.

4. CAPSULES:

Question: What are Capsules?

Answer: These are solid dosage forms in which the drug is enclosed in a hard or soft soluble container, usually made of gelatin.

Question: What are Hard shelled capsules?

Answer: Hard shelled capsules are used for powder and dry ingredients.

Question: What are Soft shelled capsules?

Answer: Soft shelled capsules are used for active ingredients that are dissolved or suspended in oil.

5. MODIFIED RELEASE DOSAGE FORMS:

Question: What are Modified Release Dosage Forms?

Answer: These forms provide either delayed or extended release of drugs. Most delayed release products are enteric-coated tablets or capsules designed to pass through the stomach unaffected, releasing their content in the intestine.

INSFFULATTONS:

Question: What are Insufflations?

Answer: These are non-toxic preparations intended for local application, such as antiseptics. They can be formulated for use in the nose, eyes, and vagina.

EXTENDED-RELEASE PRODUCTS:

Question: What are Extended-Release products?

Answer: Extended-release products are used either to protect the substance from destruction by gastric juice or to achieve a sustained release for a specific duration and location, ensuring optimum therapeutic concentrations in the blood.

B. SEMISOLID DOSAGE FORMS:

Question: What are semisolid dosage forms?

Answer: Semisolid dosage forms are preparations of semisolid consistency applied to the skin or mucous membranes for therapeutic, protective, or cosmetic purposes.

Question: List the common semisolid dosage forms.

Answer: The common semisolid dosage forms are: 1. Ointments; 2. Creams; 3. Suppository; 4. Gel/Jelly; 5. Poultice; 6. Aerosols; 7. Transdermal drug delivery system.

Question: What are Ointments?

Answer: Ointment is a homogeneous, viscous, semisolid preparation intended for external application to the skin or mucous membrane. They are used as emollients, protectants, therapeutics, or prophylactics, especially when a degree of occlusion is desired.

Question: What are the types of Ointment Bases?

Answer: The types of ointment bases are: Hydrocarbon bases (e.g., hard paraffin, soft paraffin); Absorption bases (e.g., beeswax, wool fat); Water-soluble bases (e.g., macrogols); Emulsifying bases (e.g., emulsifying wax, vegetable oils, olive oil, coconut oil, peanut oil, almond oil).

2. CREAMS:

Question: What are Creams?

Answer: Cream is a semi-solid emulsion of oil and water, divided into two groups.

Question: Describe Oil in Water (O/W) creams.

Answer: These creams are composed of small droplets of oil dispersed in a continuous aqueous (water) phase. They are more comfortable to use and are usually acceptable to patients (e.g., Vanishing cream).

Question: Describe Water in Oil (W/O) creams.

Answer: These creams are composed of small droplets of water dispersed in a continuous oil phase (e.g., Cold Cream).

3. SUPPOSITORY:

Question: What is a Suppository?

Answer: A suppository is a small, solid, medicated mass, usually cone-shaped, inserted into the rectum where it melts at body temperature. These may be used for local or systemic effects.

4. GELS / JELLIES:

Question: What are Gels/Jellies?

Answer: These are semi-solid forms where a liquid phase is confined within a 3D polymer matrix (made of natural or synthetic materials) with a high degree of physical or chemical cross-linking. They are used for medication liberation and various applications, such as carriers for spermicidal agents used intra-vaginally.

5. PASTES:

Question: What are Pastes?

Answer: Pastes are essentially ointments with a high percentage of insoluble solid added. They are less penetrating than ointments.

6. POULTICE:

Question: What is a Poultice?

Answer: A poultice is a soft and viscous preparation for external use applied to the skin for various therapeutic purposes and when a degree of occlusion is desired. They are applied warm to inflamed parts.

7. PRESSURIZED DISPENSERS/AEROSOL SPRAY:

Question: What are Pressurized Dispensers/Aerosol Sprays?

Answer: Pressurized Dispensers, known as aerosols, contain various pharmaceutical forms packaged to be distributed using propellant pressure. They are used to apply medication.

8. TRANSDERMAL PATCHES:

Question: What are Transdermal Patches?

Answer: These are medicated adhesive patches placed on the skin to deliver a specific dose of medicine through the skin and into the bloodstream. An advantage is that they provide a controlled release of medicine to the patient.

C. LIQUID DOSAGE FORMS:

Question: What are Liquid Dosage Forms?

Answer: These are prepared by dissolving, suspending, or emulsifying active drugs in an aqueous or non-aqueous solvent (e.g., alcohol, glycerin). These dosage forms can be administered topically, orally, or parenterally.

Question: What are the two main types of liquid dosage forms?

Answer: The two main types are: 1. Monophasic liquid dosage forms; 2. Biphasic liquid dosage forms.

Question: What are Monophasic liquid dosage forms?

Answer: It consists of a single liquid phase, with no visible separate layers within the liquid.

Question: Give examples of Monophasic liquid dosage forms for internal use.

Answer: Examples for internal use include Syrup, Mixture, Linctus, Elixir, and Parenteral preparations.

Question: Give examples of Monophasic liquid dosage forms for external use.

Answer: Examples for external use include Gargle, Mouthwash, Nasal drops, Lotions, and Eardrops.

Question: What are Biphasic liquid dosage forms?

Answer: It consists of two phases that are immiscible, meaning liquids are separate from each other (e.g., oil and water).

Question: Give examples of Biphasic liquid dosage forms for internal use.

Answer: An example for internal use is Emulsion.

Question: Give examples of Biphasic liquid dosage forms for external use.

Answer: An example for external use is Suspension.

PENETRATING LIQUID FORMS:

The detailed English content for "Penetrating Liquid Forms" is not explicitly visible or translated on this page, as the accompanying text is primarily in Urdu/Farsi.

1. NON STERILE LIQUIDS:

Question: How are liquids generally classified?

Answer: Liquids are classified as: 1. Non Sterile; 2. Sterile.

Question: What is a Solution?

Answer: A homogeneous mixture prepared by dissolving a drug in a suitable solvent. Solutions are intended for topical, oral, and parenteral administration.

Question: What is a Suspension?

Answer: A heterogeneous mixture composed of relatively large coarse particles dispersed in an aqueous vehicle. Suspensions may be used for topical administration. The internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation.

Question: What is an Emulsion?

Answer: An emulsion is a mixture of two or more liquids that are normally immiscible. In an emulsion, one liquid (dispersed phase) is dispersed in the other (continuous phase). The term "emulsion" comes from a Latin word meaning "to milk," as milk is an emulsion of fat and water.

Question: How are emulsions classified?

Answer: Emulsions are classified as: 1. Oil in water emulsion; 2. Water in oil emulsion.

Question: What is a Syrup?

Answer: Syrup is a concentrated aqueous preparation of sugar or a sugar substitute, with or without flavoring agents and medicinal substances. Flavoring syrups are used to mask a bad taste and contain little or no alcohol.

Question: What is an Elixir?

Answer: An elixir is a clear, sweetened, hydro-alcoholic solution intended for oral use. It is typically flavored to mask the taste of the drug and contains alcohol, which acts as a solvent. Elixirs are generally less effective than syrups in masking the taste of medicated substances.

Question: What is a Linctus?

Answer: Linctus is a liquid preparation prescribed to relieve cough. Typically, they contain a high proportion of syrup and glycerol, which have a soothing effect on throat membranes.

Question: What are Liniments?

Answer: Liniment is a medicated topical preparation applied to the skin. Unlike lotions, a liniment is applied with friction, meaning it is always rubbed on.

Question: What are Gargles?

Answer: These are aqueous solutions used for the prevention or treatment of throat infections. They are typically prepared in a concentrated solution and diluted with water before use.

Question: What are Mouthwashes?

Answer: These are similar to gargles but are used for oral hygiene and to treat infections of gums and mouth.

Advantages (of Non Sterile Liquids)

Question: What are the advantages of non-sterile liquid dosage forms?

Answer: 1. Palatable: Better for patients with difficulty in swallowing. 2. Better choice for children & old age persons. 3. More flexibility in achieving the proper dose of a medicine.

Disadvantages (of Non Sterile Liquids)

Question: What are the disadvantages of non-sterile liquid dosage forms?

Answer: 1. Shorter shelf life than other dosage forms. 2. Need special storage conditions. 3. Less stable. 4. Microbial contamination.

Enema:

Question: What is an Enema and its uses?

Answer: An enema is a procedure of introducing liquid into the rectum and colon through the anus. Evacuant enemas are used as bowel stimulants to treat constipation, and their volume may reach up to 2 liters. Barium enemas are used for diagnostic purposes.

Lotion:

Question: What are Lotions?

Answer: Lotions are liquid preparations applied to the skin or mucous membranes.

Paints:

Question: What are Paints (in a pharmaceutical context)?

Answer: Skin paints contain volatile solvents that evaporate quickly, leaving a dry prolonged contact of the medicine with the affected area. Some paints have a high glycerol content.

2. Parenteral routes:

Question: What is the definition of Parenteral Routes?

Answer: Parenteral routes involve the administration of drugs outside the digestive tract, bypassing the gastrointestinal system. This is often done to achieve a more rapid and reliable onset of action.

Question: When are parenteral routes commonly used?

Answer: It is common in emergency situations and for unconscious, non-cooperative, or patients unable to retain medication by mouth.

Question: List the common parenteral routes.

Answer: Common parenteral routes include: 1. Intravenous; 2. Intramuscular; 3. Subcutaneous; 4. Intradermal.

Question: Describe Intravenous (IV) injection.

Answer: IV injection allows for drug administration in large quantities and is used in emergencies when a rapid onset of action is needed. It should be given very slowly; for example, 10 ml should take at least 10 minutes.

Question: Describe Intramuscular (IM) injection.

Answer: IM injection involves injecting into a large muscle such as the upper and outer quadrant of the buttock, thigh, and deltoid. It provides a relatively rapid onset. Care should be taken to avoid nerves or veins. Nodules or abscesses may form if not given as prescribed.

Question: Describe Subcutaneous (SC) injection.

Answer: SC injection is suitable for drugs that require a slower release into the bloodstream, or for highly effective drugs like vaccines, insulin, and adrenaline. It is injected into the fatty tissue below the dermal layer of the skin. It is also used for diagnostic tests or certain vaccinations, such as sensitivity tests before penicillin injection.

Question: Describe Intradermal (ID) injection.

Answer: ID injection involves injecting into the dermal layer of the skin. It is often used for diagnostic tests (e.g., allergy tests, TB test) or certain vaccinations for sensitivity tests.

Types of Injections

This section primarily contains an image illustrating different types of injections: Intradermal, Subcutaneous, Intramuscular, Intravenous. Detailed descriptions are provided on Page 21.

3. Inhalation Route

Question: What are Inhalers?

Answer: Inhalers are solutions or suspensions of drugs in a mixture of inert propellants held under pressure in a container. They release a metered-dose of drug when actuated through a mouthpiece. Inhalers are commonly used to treat various respiratory conditions.

4. Nebulizer:

Question: What is a Nebulizer?

Answer: A nebulizer is a device used to administer medication in the form of a mist into the airways. It is often employed in treating asthma and other respiratory conditions by converting liquid into vapors that can be inhaled. Nebulizers are usually reserved for serious cases of respiratory diseases.

4. Topical route

Question: What does the Topical route of administration involve?

Answer: The topical route involves: 1) Application to the unbroken skin without massage or rubbing (e.g., pastes and plasters); 2) Instillation of liquid drugs into the conjunctival sac, ear, nose, or open wounds, or application of ointments and powders to these areas to obtain a local effect.

Question: What are Insufflations in the topical context?

Answer: Drug is distributed on the tissue surface to obtain a local effect (often as non-toxic antiseptics in areas like the nose, eyes, or vagina).

Question: What is Irrigation?

Answer: Urinary bladder, vagina, and urethra are irrigated by drugs.

Question: What is Insertion (e.g., Suppository, Pessary)?

Answer: Suppository and pessary are applied by inserting them on cutaneous or mucous membranes.

Question: What are Paintings (in the topical context)?

Answer: Drugs are simply applied in the form of lotions on cutaneous or mucous membranes.

Fig 1.4. Nebulizer

This is an image caption for a diagram of a nebulizer, further described under "Nebulizer" on page 22.

PHARMACOPOEIAS

Question: What are Pharmacopoeias?

Answer: Pharmacopoeias are authoritative compilations of drug information, standards, and guidelines used by health professionals and regulatory authorities. Many countries publish their own pharmacopoeias to ensure the maintenance of good drug standards.

Question: How is the British Pharmacopoeia (BP) established and used?

Answer: The BP is an official book published under the legal authority of the Government. In Pakistan, the British Pharmacopoeia (BP) is usually followed.

Question: List other major pharmacopoeias in use.

Answer: Other pharmacopoeias include: United States Pharmacopoeia (U.S.P), European Pharmacopoeia (E.P), International Pharmacopoeia (I.P), Pharmaceutical Codex (P.C), National Formulary (N.F).

Question: What are "Official Drugs"?

Answer: Drugs listed in the Pharmacopoeias are called Official Drugs.

INCOMPATIBILITIES

Question: What is incompatibility in pharmaceutics?

Answer: Incompatibility in pharmaceutics is defined as a change that results in the formation of an undesirable product, which can impact the safety, efficacy, appearance, and stability of the pharmaceutical product.

Question: What are the main types of incompatibilities?

Answer: The main types are: 1. Physical Incompatibilities; 2. Chemical Incompatibilities; 3. Therapeutic Incompatibilities.

Question: What is Physical Incompatibility?

Answer: Physical incompatibilities occur when two or more substances are combined, resulting in a physical change and the formation of an unacceptable product. This can lead to changes in color, odor, taste, viscosity, or physical state. It is also referred to as Pharmaceutical Incompatibility.

Question: List various manifestations of physical incompatibility.

Answer: Various manifestations of physical incompatibility include: 1. Immiscibility: Prescribed agents being insoluble in the vehicle. 2. Precipitation: Formation of a solid within a solution due to interaction. 3. Liquefaction: Occurs when a solid melts or becomes liquid upon mixing with another substance.

WARNING TECHNIQUE-II

THERAPEUTIC INCOMPATIBILITIES:

Question: What are Therapeutic Incompatibilities?

Answer: Therapeutic incompatibilities involve chemical reactions between substances leading to changes in the chemical properties of a pharmaceutical product. These can result in the formation of toxic or inactive products, or changes that include pH changes, oxidation-reduction reactions, acid-base hydrolysis, complex formation, precipitation, effervescence, decomposition, color change, or explosion.

Question: Give an example of therapeutic incompatibility.

Answer: Therapeutic incompatibility occurs when two or more drugs are administered simultaneously. For example, antibiotics like tetracycline should not be administered simultaneously with calcium-containing products (like milk) because calcium interferes with the absorption of tetracycline, reducing its antibacterial effects. This highlights the importance of checking drug administration.

Question: How are mechanisms of therapeutic incompatibility divided?

Answer: Mechanisms of therapeutic incompatibility are divided into two groups: Pharmacokinetic incompatibility and Pharmacodynamic incompatibility.

Question: What is Pharmacokinetic Incompatibility?

Answer: It involves the effects of one drug on another in terms of absorption, distribution, metabolism, and excretion.

Question: What is Pharmacodynamic Incompatibility?

Answer: It relates to the pharmacological activity of interacting drugs, including synergism, antagonism, altered cellular transport, and effects on receptor sites. Some drugs are contraindicated due to their pharmacodynamic incompatibility, such as drugs with opposing pharmacological actions or drugs that potentiate toxicity.

Question: What is "Prescribing Contra-indicated Drugs"?

Answer: Certain drugs may be contraindicated in specific diseases or for patients allergic to them. For instance, penicillin and sulfur drugs are contraindicated in patients with allergies.

Question: Explain Synergistic or Antagonistic Drug Reactions.

Answer: Synergism occurs when two drugs increase each other's activity, while antagonism occurs when two drugs decrease each other's activity. Proper consideration of drug interactions is essential for safe and effective prescribing.