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• Pharmacology pertains to the study of the mechanisms, uses, and adverse effects of drugs, excluding the preparation and dispensing of medications.
• Drugs are chemical agents that can either stimulate or inhibit existing cell functions, rather than creating new ones.
• Pharmacogenetics examines how a single genetic variation impacts drug metabolism, efficacy, and toxicity.
• Pharmacogenomics studies how an individual's entire set of genes influences their response to drugs.
• Pharmacodynamics investigates effects of drugs on the body, focusing on their biological and therapeutic actions.
• Pharmacokinetics studies the body's effect on drugs, including absorption, distribution, metabolism, and excretion.

Sources and Nature of Drugs

• Drugs can be derived from various sources including plants, for example bark of cinchona yields quinine
• Belladonna leaves are a source of atropine
• Opium poppy provides morphine.
• Animal sources are also used; for example, insulin comes from pork and beef
• Vaccines, sera, and vitamins are products of animal sources.
• Drugs can also be synthetically produced, such as aspirin, sulphonamides
• Local anesthetics are synthetic sources.
• Mineral sources like iron for hypochromic anemia
• Iodine for hyperthyroidism
• Magnesium sulphate for constipation treatment are used.
• Microorganisms can make antibiotics like penicillins.
• Genetic engineering enables the production of drugs identical to human hormones.

Dosage Forms of Drugs

• Drugs come in liquid forms, solid forms, and preparations for external application.
• Liquid forms include solutions, suspensions, syrups, and parenteral drugs.
• Solutions are drug preparations dissolved in a solvent, like 5% dextrose in water.
• Suspensions involve drugs that do not fully dissolve and tend to separate, requiring shaking before use, such as penicillin.
• Syrups suspend drugs in sugar and water for improved taste, exemplified by cough syrups.
• Parenteral drugs are liquid forms administered via IM, IV, or SC routes, often used in emergency medicine.
• Solid forms include pills and tablets, which are easy to swallow.
• Tablets consist of compressed powder, often sugar-coated for better taste.
• Suppositories mix with a base that melts at room temperature (21°C), dissolving and absorbing after rectal or vaginal insertion.
• Capsules are drugs enclosed in gelatin, with hard capsules typically containing powdered drugs and soft capsules containing liquids
• Sustained-release tablets consist of drug particles coated to dissolve at varying rates, providing a prolonged effect, as seen with antihistamines.
• Preparations for external use include ointments and lotions, applied to the skin or mucous membranes, like eye and nasal dropsused topically
• Enemas are administered into the rectum.

Routes of Drug Administration

• Drug administration routes can be classified as systemic or local.
• The route chosen is determined by the effect desired.
• Local drug administration targets a specific site directly, while systemic affects entire body. The route depends on whether a local or systemic effect is desired.
• Localized drugs are characterized by concentrating the drug at the desired site and minimizing systemic side effects.
• The systemic approach is used when the target is not directly accessible.

Local Administration

• Drug is applied directly to the target area in a suitable concentration.
• Achieved through topical application, inhalation, or injection.
• Topical applications are applied directly to the skin.
• Inhalation involves delivering drugs through the respiratory tract to treat broncho-pulmonary diseases
• Beta agonists and corticosteroids are delivered via inhalation
• Injection involves administering drugs around sensory nerve terminals, nerve trunks, or joints, with the potential for adverse effects.

Systemic Administration

• Enables a drug to be absorbed and circulate to different body tissues.
• Two main routes: alimentary (enteral) and parenteral.
• Alimentary routes involve oral, buccal, and rectal administration.
• Parenteral routes use intravenous, intramuscular, subcutaneous injection or infusion.
• Oral route is convenient, but can also be unsuitable for several reasons
• Mouth(swallowed) or oral administration involves swallowing a medication
• Buccal route involves placing a sublingual tablet under the tongue.
• The Rectum involves drug administration through the rectum

Alimentary (Enteral) Routes

• This route includes oral, sublingual, and rectal administration.
• In general, the drug should be palatable, non-irritant, and stable at stomach pH
• Safe, easy to administer, and economic methods with no need for sterilisation and no need for medical staff to administer
• Disadvantages: delayed onset of action unsuitable in emergency situations.
• Not practical in unconscious or uncooperative patients.
• Some drugs are destroyed in the gastrointestinal tract, others some drugs are not absorbed through the gut
• Some tablets lodge in the esophagus, causing delayed action and ulceration.

Buccal

• Provides a quick effect due to abundant blood supply in the oral mucosa.
• Avoids liver first-pass metabolism.
• Irritation of the mucous membrane.
• Excessive salivation promotes swallowing, reducing benefits.

Rectal

• Suitable for drugs that irritate the stomach.
• Rapid abortion occurs due to the high density of blood vessels
• Partially avoids first-pass metabolism.
• Useful for patients who cannot swallow or are vomiting.
• Disadvantages include psychological resistance, potential rectal inflammation, and unreliable absorption.
• Absorption can be unreliable esp if a patient has fecal impaction
• Examples include aminophylline and indomethacin.

Parenteral Routes

• Alternative routes that bypass the gastrointestinal tract, respiratory tract, or skin.
• The most common parenteral routes are intravenous, intramuscular, the or subcutaneous injection.

Advantages of Parenteral Routes

• Suitable for uncooperative, unconscious, or nauseous patients.
• Effective for drugs ineffective when taken orally
• Intravenous route shows immediate onset of drug action in emergencies.
• Compliance problems are avoided.
• Useful for fluid and electrolyte imbalances, providing nutrients and calories.

Disadvantages of Parenteral Routes

• Requires trained personnel.
• Involves aseptic procedures.
• Patients may have a fear of needles
• Drug effects are difficult to reverse.

Intravenous Administration

• Direct injection into the systemic circulation.
• Suitable for patients vomiting or unconscious, and for drugs that are irritant
• Not suitable for oily solutions and poorly soluble substances.

Intravenous Infusion

• Used when oral intake is inadequate, like in unconscious patients.
• Avoids the liver
• Also used when patients post operative.
• And after blood transfusions.

Intramuscular Injection

• It is rapid injection, used for lipid or water soluble drugs
• Avoids with liver first pass metabolism
• Well absorbed when body exercises
• Requires trained personnel.
• Painful, must be sterilized
• Poor absorption
• Decreased absorption
• Complications of nerve irritation and abscess formatio

Subcutaneous Route

• Onset of drug action is faster in comparison to the oral route
• Avoids gastrointestinal absorption problems
• Some drugs will irritate tissues and cause pain
• Must involve sterile technique because breaks skin barrier.
• Slower than the action of intramuscular drug administration.
• And is more expensive than oral.
• Best practiced with assistance

Inhalation as Systemic Route

• Includes general anesthesia, nitrous oxide administration, and inhaled analgesics.
• Offers rapid absorption for systemic effect and high local concentration
• But is irritant for pulmonary