Introduction to Pharmacology

Study Notes

Pharmacology

Pharmacology is the study of how drugs work.
This science is critical for medicine, pharmacy, nursing, dentistry, and veterinary medicine.
Pharmacology examines how chemicals affect cells and treats and prevents major diseases.

Pharmacology: Key Areas

Pharmacokinetics: How drugs are absorbed, distributed, and eliminated in the body.
Pharmacodynamics: How drugs act on specific biological systems.

Drug Sources

Natural: Drugs from plants, microbes, animal tissues, and minerals.
- Alkaloids are a major compound found in plants with pharmacological activity.
- Examples:
  - Morphine, cocaine, quinine, and atropine (alkaloids)
  - Artemisinin (from Artemisia annua) is an antimalarial agent.
- Antibiotics are isolated from microorganisms like penicillin and streptomyces.
- Insulin (used by diabetic patients) is obtained from pigs and cattle.
- Minerals like iron and potassium are extracted from the earth.
Synthetic: New drugs created in laboratories.
- Examples: Aspirin, procaine (local anesthetic), paracetamol, phenytoin (anticonvulsant).
Semi-synthetic: Modified drugs derived from natural sources.
- Modifications of existing natural compounds.
- Example: Artemether (an antimalarial drug) derived from artemisinin.
- Other examples: Heroine from morphine, homatropine from atropine.

Solid Dosage Forms

Solid forms (tablets, capsules, lozenges, granules, powders):
- Advantages: Good stability, easy packaging, easy dispensing, accurate dosing.
- Disadvantages:
  - Difficult to swallow, slow onset of action, may be degraded in the stomach.
Tablets:
- Available in many sizes, shapes, and colors.
- Made by compressing active ingredients and inert substances.
- Can be scored for easy breaking.
- Chewable tablets have flavored or colored bases.
- Delayed-release tablets allow for less frequent dosing and reduced side effects.
- Enteric-coated tablets are protected from stomach acid with a coating.
- Film-coated tablets dissolve quickly in the stomach, covering taste and odor.
Caplets:
- Shape of capsules, easier to swallow, more stable than capsules.
Capsules:
- Contain the drug in a hard or soft gelatin shell.
- Shell dissolves in the stomach, releasing the drug.
- May contain powders, granules, or liquids.
- Can have delayed-release properties.
Lozenges:
- Hard, oval, or round solid dosage forms with a flavored sugar base.
- Dissolve in the mouth (local therapeutic effects).
- Commonly used for sore throats.
Powders and Granules:
- Powders: Extremely fine, dry drug used topically or orally.
- Granules: Larger than powders, more stable.
Suppositories:
- Inserted into the rectum (rectal suppository) or vagina (vaginal suppository).
- Base melts or dissolves, releasing the medication.
- Used for local or systemic drug delivery.
- Commonly used in children and those unable to take oral medications.

Semi-solid Dosage Forms

Used topically: skin, mucous membranes, nasal, rectal, or vaginal cavities.
Examples: creams, lotions, gels, and pastes.
Creams
- Oil-in-water (O/W) emulsion: Small amount of oil dispersed in water.
- Easy to massage into the skin without leaving an oily residue.
- Can be formulated for rectal or vaginal use.
Lotions
- Thinner than creams.
- More water than creams.
- Penetrate the skin, cover large areas without leaving an oily residue.
Gels
- Contain solid medication particles in a thick liquid.
- For internal and external use.
- Particles are ultrafine and linked to form a semisolid material.
- Penetrate the skin without leaving a residue.
Pastes:
- More solid material and less liquid base.
- Stiffer, less greasy, applied thicker.

Liquid Dosage Forms

Solutions and suspensions are the most common liquid formulations.
Administered orally, parenterally (injectable), or other routes.
Convenient for administering medications to children and those unable to swallow solid forms.
Less convenient for frequent dosing because the liquid must be measured each time.
- Solutions and suspensions for oral administration are often sweetened and flavored for better taste.
- Syrups: Sweetened aqueous solutions.
- Elixirs: Sweetened aqueous-alcoholic solutions.
- Sterile solutions and suspensions: Available for parenteral administration (injections).
- Sterile powders for injection are mixed with sterile liquids before injection.