Basic Pharmacology Lecture 1, Dr. Mona Gaafar PDF

BASIC PHARMACOLOGY (CPO 302)  1- Pharmacokinetics BY Associate Prof. Mona Gaafar Pharmacology Is a term derived from the greek word pharmacon (a drug or poison) and logy (the science). It is the science that deals with drugs. Pharmacology is the science that dea...

BASIC PHARMACOLOGY (CPO 302)  1- Pharmacokinetics BY Associate Prof. Mona Gaafar Pharmacology Is a term derived from the greek word pharmacon (a drug or poison) and logy (the science). It is the science that deals with drugs. Pharmacology is the science that deals with the drugs regarding classification, pharmacokinetics, pharmacodynamics, side effects and therapeutic uses.. Drug Is defined as a substance that is used for prevention, diagnosis, treatment and cure of the disease in animals and humans. Pharmacokinetics Describe what the body does to the drug. It is the study of Absorption, Distribution, Metabolism (biotransformation) and Excretion of drugs. Pharmacodynamics: It is the study of pharmcological and physicological effects of drugs & Mechanism of action of drugs Pharmacogenomics (or pharmacogenetics): Study of the genetic variations that cause individual differences in drug response. BRANCHES OF PHARMACOLOGY: ❑Medical pharmacology : Chemicals administered to achieve a beneficial therapeutic effect on some process within the patient or for their toxic effects on regulatory processes in parasites infecting the patient. ❑Toxicology is the branch of pharmacology that deals with the undesirable effects of chemicals on living systems. Pharmacokinetics of drugs Are studies of drugs regarding ADME ❑ Absorption ❑ Distribution ❑ Metabolism ❑ Excretion  PHARMACOKINETICS Particularly, Examine the movement of a drug over time through the body. Pharmacological as well as toxicological actions of drugs are primarily related to the plasma concentrations of drugs. Thus, the clinician must recognize: ✓the speed of onset of drug action, ✓the intensity of the drug's effect, ✓and the duration of drug action Those can be controlled by four pathways : # first, drug absorption from the site of administration (absorption) permits entry of the therapeutic agent (either directly or indirectly) into plasma. # Second, the drug may then reversibly leave the bloodstream and distribute into the interstitial and intracellular fluids (distribution). # Third, the drug may be metabolized by the liver, kidney, or other tissues (metabolism). # Finally, the drug and its metabolites are removed from the body in urine, bile, or feces (elimination). Onset of action (Onset time) is the duration of time it takes for a drug's effects to come to prominence upon administration. With oral administration, it typically ranges anywhere from 20 minutes to over an hour, depending on the drug in question. The peak time (tmax): is the time at which the body displays the maximum plasma concentration  Routes of drug administration ( Enteral- Parenteral) ENTERAL VIA GASTROINTESTINAL TRACT (GIT). ❖ ORAL ❖ SUBLINGUAL ❖ RECTAL PARENTERAL ADMINISTRATION = INJECTIONS. TOPICAL APPLICATION INHALATION ENTERAL ROUTES A. ORAL B. SUBLINGUAL C. RECTAL  PARENTERAL ROUTES IV / intravascular SC / subcutaneous IM / intramuscular Routes of drug administration ( Enteral- Parenteral) The route of administration is determined by: 1- The properties of the drug (for example, water or lipid solubility, ionization, etc.) 2- The therapeutic objectives (for example, the desirability of a rapid onset of action or the need for long-term administration or restriction to a local site). I- Enteral : - drug is swallowed, allowing oral delivery: Some drugs are absorbed from the stomach * Most drugs are absorbed from the duodenum because of its larger absorptive surface. - The drug is placed under the tongue (sublingual), facilitating direct absorption into the bloodstream without destruction in GIT A- oral route:  A- oral route: - These drugs undergo first-pass metabolism in the liver, where they are extensively metabolized before entering the systemic circulation, Oral Dosage Forms (oral formulations) Tablets Coated tablets: sugar-coated to mask bad taste Enteric coated tablets: dissolve only in intestine Capsules Hard gelatin capsules: (contain powder) Soft gelatin capsules: (contain liquid) Syrup (e.g. Cough syrups) Suspension (mixture of solid in liquids e.g. antibiotics).  B. SUBLINGUAL - Placement under the tongue Advantages: ✓Allows the drug to diffuse into the capillaries & therefore to enter the systemic circulation (rapid absorption) ✓Rapid onset ( can be used in emergincies) ✓Excess drug can be removed easily from the mouth. ✓The drug bypasses 1st pass effect SUBLINGUAL C. RECTAL Used when oral route is unavailable Useful if - The drug induces vomiting if given orally or if the patient is already vomiting or unconscious - Bypasses first pass effect by certain extent (50%). - Suitable for children. Rectal route: Fifty percent of the drainage of the rectal region bypasses the portal circulation; thus, the biotransformation of drugs by the liver is minimized. Like the sublingual route of administration, the rectal route of administration has the additional advantage of preventing the destruction of the drug by intestinal enzymes or by low pH in the stomach. The rectal route is also useful if the drug induces vomiting when given orally, if the patient is already vomiting, or if the patient is unconscious. [Note: the rectal route is commonly used to administer antiemetic agents.] On the other hand, rectal absorption is often erratic and incomplete, and many drugs irritate the rectal mucosa. c. Rectal route  II- Parenteral: The three major parenteral routes are intravascular (intravenous or intra-arterial), intramuscular, and subcutaneous. Advantage: - I is used for drugs that are poorly absorbed from the GI tract (for example heparin) and for agents that are unstable in the GI tract (for example, insulin). - Used for treatment of unconscious patients - Highest bioavailability and not subject to first-pass metabolism or destruct in GI environments. - Provides the most control over the actual dose of drug delivered to the body. Disadvantage: may cause pain, fear, and infections.  PARENTERAL 1. Intravascular a- IV (intravenous) - For drugs which are not absorbed orally - Bypasses the liver - 100% of drug reaches circulation. - Permits a rapid onset (rapid effect) and a maximal degree of control over the circulating levels of the drug. Disadvantage: - Can not detoxified by emesis or by binding to activated charcoal. - May introduce bacteria through contamination at the site of injection. - It may cause hemolysis or cause other adverse reactions by the too-rapid delivery of high concentrations of drug to the plasma and tissues. Therefore, the rate of infusion must be carefully controlled. b- IM / intramuscular aqueous soln (rapid absorption) Drugs administered specialized depot preparations (aquous suspension or oily solutions)… slow absorption B. Intramuscular (IM): Drugs administered IM can be aqueous solutions or specialized depot preparations often a suspension of drug in a non-aqueous vehicle such as polyethylene glycol. Absorption of drugs in an aqueous solution is fast, whereas that from depot preparations is slow. The drug then dissolves slowly, providing a sustained dose over an extended period of time. An example is sustained-release haloperidol decanoate, which slowly diffuses from the muscle and produces an extended neuroleptic effect.. C. SC / SUBCUTANEOUS - Slower absorption than IV & IM due to low vascularity (blood supply to this tissues is poor). - Suitable for insulin injection. 3-OTHER ROUTES OF DRUG ADMINISTRATION A- Inhalation - Provides a rapid delivery of a drug across a large surface area of the mucus membranes of the respiratory and the pulmonary epithelium - Effect is as rapid as iv injection - Used for gaseous & volatile liquid- powder drugs. This route is particularly effective and convenient for patients with respiratory complaints (such as asthma, or chronic obstructive pulmonary disease) because the drug is delivered directly to the site of action and systemic side effects are minimized. Examples: albuterol, and corticosteroids, such as fluticasone B- INTRANASAL - Through the nose - Eg. : Calcitonin in osteoporosis Cocaine in addicts C- TOPICAL (LOCAL) - Is used when a local effect of a drug is required - Eg., Ointments, lotions, plasters Topical application: Is used when a local effect of the drug is desired. For example, ketoconazole is applied as a cream directly to the skin in the treatment of dermatophytosis. D- Transdermal route: Achieves systemic effects by application of drugs to the skin, usually via a transdermal patch. This route is most often used for the sustained delivery of drugs, such as the antianginal drug nitroglycerin, the antiemetic scopolamine, and the once-a-week contraceptive patch that has an efficacy similar to oral birth control pills. TRANSDERMAL ROUTE E. INTRATHECAL, Introducing drugs directly into the cerebrospinal fluid / CSF and CNS by avoiding BBB For example, amphotericin B is used in treating cryptococcal meningitis INTRAARTICULAR