Pharmacology Concept of Prodrug | CHAPTER-3 | Pharmacology

Pharmacology Concept of Prodrug – This book covers the entire syllabus of “Pharmacology” prescribed by BNMC- for diploma in nursing science & midwifery students. We tried to accommodate the latest information and topics. This book is an examination set up according to the teachers’ lectures and examination questions.

At the end of the book, previous questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.

Pharmacology Concept of Prodrug

Definition of Prodrug:

A chemical that is readily absorbed & distributed & then converted to the active drug by biological process inside the body is called a prodrug.

[Ref-Katzung/14/71]

Or,

There are some chemical substances which do not produce pharmacological effects until they are chemically altered within the body. Such chemical substances are called prodrug.

[Ref-Misbahuddin/5/5]

Significance/Purposes/Advantages of Prodrug:

Prodrugs are designed to overcome pharmaceutical and/or pharmacokinetically based problems associated with the parent drug molecule that would otherwise limit the clinical usefulness of the drug. The scientific rationale, based on clinical, pharmaceutical and chemical experience, for the design of various currently used prodrugs is presented in this review.

The examples presented are by no means comprehensive, but are representative of the different ways in which the prodrug approach has been used to enhance the clinical efficacy of various drug molecules.

• It increases palatability.
• It increases both oral (e.g. Enalapril, Talampicillin) & topical (e.g. Triamcinolone) absorption.
• It increases bioavailability & reduces 1st pass hepatic metabolism.
• It increases distribution.
• It increases duration of action.
• It modifies biotransformation.
• It modifies excretion.
• It reduces adverse effects.
• To overcome difficulties encountered in pharmaceutical formulation procedure.

Disadvantages of prodrug:

• Time to reach peak plasma concentration is more than active drug
• Potency of some drugs is decreased.

Biological drugs:

The drugs that are obtained from living sources are called biologic drugs.

Or,

A biologic medicine is defined by the European legislation as ‘a medicine that contains one or more active substances made by or derived from a biological source. In the broadest sense, biological medicines include any substance made in the laboratory from a living organism.

Examples of biological drugs:

• Insulin (human or porcine).
• Heparin (beef lung, hog intestine)
• Different vaccines (microorganisms).
• Immunoglobulins (Ig) [horse serum],
• Histamine (mast cell)

Characteristics of Biological Drugs:

• Chemistry: Protein & polypeptide in nature.
• Route: Not suitable for oral route as they are metabolized in the stomach & GIT by proteolytic enzymes. So, must be given in parenteral route.
• Antigenicity: As they are protein in nature & biological products they are susceptible for hypersensitivity reaction.
• Storage: They must be kept in 4°C. Otherwise the protein will be denatured.
• Comparatively costly

Recombinant DNA technology:

The genetic manipulations in the laboratory involving the isolation and cloning of a specific DNA are collectively referred to as recombinant DNA technology.

Biomedical importance/uses/significance:

Recombinant DNA technology has a wide range of applications, such as –

1. Understanding of molecular basis of a number of diseases (e.g. sickle cell anemia, thalassemia, familial hypercholesterolemia etc.)

2. Production of large amount of human protein for therapy (e.g. insulin, GH)

3. Production of proteins for vaccines (e.g. HBV vaccine) & for diagnostic testing (e.g. AIDS tests).

4. Application to forensic medicine, e.g. identification of criminals, paternity tests.

5. Gene therapy for sickle cell anemia, Thalassemia.

6. Prenatal diagnosis of genetic disease.

7. Tissue typing (HLA typing) for organ transplantation.

[Ref-Harper/28/396]

Example of prodrug:

Definition of Excipient:

Excipient; Additional chemical substances that are used in drug production having no drug property, is called excipient.

Components of excipient:

1. Diluents: Form bulk of drug (shape, size); e.g. Dextrose, lactose, starch, sucrose etc.

2. Binder: They bind several drug molecules to prevent auto breakdown. It is known as shelf life; e.g. Methyl cellulose.

3. Flavoring agent: Orange flavor, peppermint oil etc. are the flavoring substances.

4. Disintegrating agent: To break the drug molecule before absorption; e.g. Starch, vee gum.

5. Lubricant: To lubricate drug molecule, e.g. stearic acid, Ca-stearate; Mg-stearate, talc.

6. Coloring substances: To color drug for identification, attraction etc. e.g. brilliant blue, caramel etc.

7. Sweetening agent: To make a drug sweet taste; e.g. saccharin, lactose, mannitol etc.

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