Introduction to Pharmacology

Dr. Karun Kumar

JR – II

Dept. of Pharmacology

Definition

• Pharmacology Study of drugs & their effects on life processes

• Pharmakon

Earlier Magic charm for treating disease

Later Remedy or drug

History of pharmacology

• 1st phase Noxious plant & animal prep. Were admin. To diseased patient to rid the body of evil spirits believed to cause illness

• 2nd phase Experience enabled people to understand which subst. were beneficial in relieving particular disease symptoms

• 3rd phase Rational or scientific phase (Advances in chemistry & physiology; understanding of disease mechanisms)

• 1st effective drugs Simple external prep. (cool mud or soothing leaf)

• 1500 BC Egyptian presc. (castor oil, opium)

• China Ancient scrolls (herbal medicines)

• Dioscorides (Greek army surgeon) > 600 medicinal plants that he collected in his trip

• Susruta (Hindu physician) Ayurvedic medicine

• Isolation of pure drug compounds from natural sources

1. Isolation of morphine from opium 1804

2. Magendie & Bernard Curare eff. On NMJ

• 1st med school Pharma lab Rudolf Buchheim in Estonia

• Buchheim & 1 of his students (Oswald Schmiedeberg) trained many others including John Jacob Abel

• Sir Colonel Ram Nath Chopra 1st to establish a center of study and research in pharmacology in India, at the Calcutta School of Tropical Medicine

• 1st pharmacology dept. Estd. At University of Michigan (1891) by John Jacob Abel

20th century developments

• Isolation & use of insulin for DM

• Discovery of antimicrobials

• Discovery of antineoplastic drugs

• Advent of modern psychopharmacology

• Pharmacology & its subdivisions Pk, pd

• Toxicology Study of poisons and organ toxicity

• Pharmacotherapeutics Use of drugs in the treatment of disease

• Pharmacy Science and profession concerned with the preparation, storage, dispensing, and proper use of drug products

• Pharmacognosy study of drugs isolated from natural sources including plants, microbes, animal tissues, and minerals.

• Medicinal chemistry Specializes in the design and chemical synthesis of drugs

• Pharmaceutical chemistry or pharmaceutics Formulation and chemical properties of pharmaceutical products, such as tablets, liquid solutions and suspensions, and aerosols

Natural sources of drugs

• Alkaloids Substances that that contain nitrogen groups and produce an alkaline reaction in aqueous solution

• Structure-activity relationship Relationship among the drug molecule,its target receptor, and the resulting pharmacologic activity Eg inhibit angiotensin synthesis, treat hypertension, and anti (HIV).

Drug preparations

• Crude drug preparations Obtained from natural sources

• Pure drug compounds From natural sources or synthesized in the laboratory

• Pharmaceutical preparations Intended for administration to patients

Crude drug preparations

1. Drying or pulverizing a plant or animal tissue

2. Extracting substances from a natural product with the aid of hot water or a solvent such as alcohol. Eg. coffee and tea, made from distillates of the beans and leaves of Coffea arabica and Camellia sinensis plants, and opium, which is the dried juice of the unripe poppy capsule of the plant Papaver somniferum.

Pure drug compounds

• Frederick Sertürner isolated the fist pure drug from a natural source when he extracted a potent analgesic agent from opium in 1804 and named it morphine, from Morpheus, the Greek god of dreams

• Frederick Banting and John Macleodi Isolation of insulin from the pancreas

Drug sources & preparations

Dosage forms

• Drug products suitable for administration of a specific dose of a drug to a patient by a particular route of administration

• Solid dosage forms Tablets, Capsules, SR/ER

• Liquid dosage forms Solutions, suspensions, syrups, elixirs

Tablets & Capsules

• Most common preparations for oral administration

• In the manufacture of tablets, a machine with a punch and die mechanism compresses a mixture of powdered drug and inert ingredients into a hard pill

• Inert ingredients include

1. Fillers Specific components that provide bulk

2. Lubricants prevent sticking to the punch and die during manufacture

3. Adhesives Maintain tablet stability in the bottle

4. Disintegrants Facilitate solubilization of the tablet when it reaches gastrointestinal fluids

Enteric coated tablets

• Consist of polymers that will not disintegrate in gastric acid but will break down in the more basic pH of the intestines

• Used to protect drugs that would be destroyed by gastric acid and to slow the release and absorption of a drug when a large dose is given at one time, for example, in the formulation of the antidepressant floxetine, called PROZAC WEEKLY

SR/ER preparations• Release the drug from the preparation over many hours.

• 2 methods to extend the release of a drug

1. Controlled diffusion Release of the drug from the pharmaceutical product is regulated by a rate-controlling membrane

2. Controlled dissolution Done by inert polymers that gradually break down in body fluids

• Some products use osmotic pressure to provide a sustained release of a drug. These products contain an osmotic agent that attracts gastrointestinal fluid at a constant rate. The attracted fluid then forces the drug out of the tablet through a small laser-drilled hole

Capsules

• Hard capsules Enclose powdered drugs

• Soft capsules Enclose a drug in solution

• The gelatin shell quickly dissolves in gastrointestinal fluids to release the drug for absorption into the circulation

Solutions and suspensions

• Syrups Sweetened aqueous solutions

• Elixirs sweetened aqueous-alcoholic solutions are known as elixirs. Alcohol is included in elixirs as a solvent for drugs that are not suffciently soluble in water alone.

• Sterile solutions and suspensions Parenteral administration

• Sterile ophthalmic solutions and suspensions Eyedropper into the conjunctival sac

Skin patches

• Drug preparations in which the drug is slowly released from the patch for absorption through the skin into the circulation

• Most suitable for potent drugs, which are therefore effective at relatively low doses, that have sufficient lipid solubility to enable skin penetration

Aerosols

• Aerosol Administered by inhalation through the nose or mouth

• Ointment & creams semisolid preparations intended for topical application . They contain an active drug that is incorporated into a vehicle (e.g., polyethylene glycol or petrolatum) which enables the drug to adhere to the tissue for a sufficient length of time to exert its effect

• Lotions Liquid preparations often formulated as oil-in-water emulsions and are used to treat dermatologic conditions.

• Suppositories Products in which the drug is incorporated into a solid base that melts or dissolves at body temperature. Used for rectal, vaginal, or urethral administration

Routes of drug administration

1. Enteral (Drug abs. through GIT)

• Sulblingual under tongue ; no fpm (lipid soluble); NG, hyoscyamine

• Buccal b/w cheek and gum; no fpm (lipid soluble); lollypop of Fentanyl (breakthrough cancer pain)

• Oral PO (per os by mouth)

• Rectal (N/V; little fpm) Local - Haemorrhoids

Oral route

2. Parenteral

• I.v.

• I.m. and S.c. Drug solns. & particle suspensions

• Intrathecal subarachnoid space (meningitis)

• Epidural Labor & delivery (above the dura)

• Intraart. arthritis ; intrad. all.; insufflation (intranasal admin.) sinus medications

• Transdermal NG ointment for HF & angina; Fentanyl transdermal for chr. Pain (skin patch/oint)

• Inhalational Local (Anti-asthma / rhinitis) systemic (GA Sevoflurane)

• Topical Surface of body (Skin, eyes, nose, mouth, throat, rectum, vagina)

Drug names

1. Chemical acetylsalicylic acid (chemists)

2. Nonproprietary (generic) USAN (US adopted name) class to which drug belongs oxacillin is a type of Pn; INN (Intl. nonpropr. Name); BAN (British approved name)

3. Proprietary (brand) Flomax for Tamsulosin; Diuril for chlorothiazide; Maxair Pirbuterol