What is Pharmacology?

It is the science that deals with the study of chemical substances (drugs).

The study of drug: - How they work?

- What they are?

- What they do?

What is Toxicology?

It is a branch of pharmacology which deals with the undesirable effects of chemicals and drugs on living system.

Drugs (Therapeutic agent):-

Definition (Def.): Any substance other than food can be used in prevention, diagnosis, or treatment of diseases.

Sources of drugs:

1) Natural 2) Synthetic Plant

Plant e.g. Pilocarpine. Chemically e.g. Sulphonamides.

Animal e.g. Heparin. Genetic engineering (rDNA technology)

Microorganisms e.g. Antibiotics. e.g. Human insulin.

Minerals e.g. Ferrous sulfate.

Names of drugs:

1) Chemical name e.g. Acetylsalicylic acid

2) Generic name e.g. Aspirin

3) Trade name e.g. Rivo

ROUTES OF ADMINISTRATION

1: Oral route:-

 Advantage:

-Non irritant

-Palatable

-Most common

-Safer

-Easy of administration

- Economic

 Disadvantage:

- Not suitable for patient suffering from vomiting and diarrhea.

- Not suitable in emergency

- Affected by PH.

- First Pass Effect (Pre-systemic metabolism): (Decrease bioavailability of drug)

Def. of First Pass Effect:

Inactivation or elimination of part or whole of the drug before reaching the systemic circulation.

• Sites:

1) Gut first pass effect:

Gastric acidity.

Digestive enzyme

Mucosal enzyme

2) Hepatic First pass effect:

To overcome hepatic first pass effect:

If partial Increase the dose of the drug.

If complete Use another routes such as IV and sublingual.

Factors affecting oral absorption:-

1: Presence of food and other drugs in the GIT:

Amino acids compete for the same carrier of L-dopa.

-Ca (from milk) decrease absorption of tetracycline.

- Tannic acid (from tea) and tetracycline V absorption of iron.

- Food dilutes drugs and decrease absorption.

* Food is useful in irritant drugs to decrease irritation.

2: State of health of GIT:

Presence of the disease in the GIT decreases absorption.

3: Gastric emptying rate:

May be increase or decrease absorption (depend on the drug):

For Example in high emptying rate

- Increase absorption of Paracetamol (Rapid rate of dissolution and disintegration)

- Decrease absorption of Digoxin (Slow rate of dissolution and disintegration) Atropine decreases

motility of the GIT decrease emptying rate.

4: Motility of GIT:

- Increase Motility (Diarrhea) decrease absorption.

-Decrease Motility (Constipation) Increase absorption.

5: PH of GIT:

- Acidic drugs (Aspirin) - absorbed in acidic medium (Stomach).

Basic drugs (Ephedrine) absorbed in basic medium (Intestine).

6: First pass effect:

= Decrease bioavailability.

7: Related to the drug: (Lipid solubility)

- Lipid soluble drugs Increase absorption.

- Polar drugs (water soluble drug) not totally absorbed (due to high amount of lipid content in the

cells) and not pass through Blood Brain Barrier (BBB).

- Non-polar drugs (Lipid soluble drugs) highly absorbed and Pass BBB.

2: Parenteral routes (injections):

A: Intravenous (IV) injection:

Advantage:

- 100% bioavailability (The amount of drug reached to blood).

- No first pass effect.

- Suitable for irritant drugs.

- Suitable in emergency.

- Suitable for acid labile drugs.

Disadvantage:

- Low safety (May cause allergy or anaphylactic shock).

- Must be sterile (Pyrogenic reaction).

- Spreading of infection (Viral hepatitis).

- Required professional person.

- Not suitable for oily and suspended drugs.

B: Intramuscular (IM) injection:-

- Suitable for solution, suspension and oily drugs.

- Better absorption than SC but less than IV.

C: Subcutaneous (SC) injection:-

- Absorption rate is slower than IV and IM.

- It is suitable for drugs that are non-irritant in aqueous solution or fine suspension.

D: Intradermal (ID) Injection:

- Sensitive tests.

E: Other injection:-

- E.g. - Intra-cardiac -Intra-bone marrow

- Intrathecal - Intra-peritoneal

3: Mucosal route:

- Buccal or Sublingual Systemic delivery of drug

-Ocular Local delivery of drugs

-Vaginal, Nasal and Rectal Systemic or local delivery of drugs

4:Inhalation:-

- Systemic delivery of drugs.

- Highly blood supply and wide surface area.

- Highly absorbed (high bioavailability).

- Many drugs make lung irritants.

5:Topical:-

- Usually local effect but high lipid soluble drugs can be absorbed.

- Transdermal drug delivery system (TDDS) enhance skin absorption e.g. Skin patches of nicotine. 

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