Introduction To Pharmacology And Routes Of Administration PDF

INTRODUCTION TO PHARMACOLOGY AND ROUTES OF ADMINISTRATION Prof Dr Norazlina Mohamed Dept of Pharmacology Faculty of Medicine, UKM  WHAT IS PHARMACOLOGY? from Greek: φάρμακον, pharmakon - "drug"; and -λογία, -logia – the study of). Thus pharmacology is the study of drug. ...

INTRODUCTION TO PHARMACOLOGY AND ROUTES OF ADMINISTRATION Prof Dr Norazlina Mohamed Dept of Pharmacology Faculty of Medicine, UKM  WHAT IS PHARMACOLOGY? from Greek: φάρμακον, pharmakon - "drug"; and -λογία, -logia – the study of). Thus pharmacology is the study of drug.  PHARMACOLOGY The science or study of drugs The study of interaction between drugs and biological system Involves what the body does to the drug pharmacokinetic and what the drug does to the body pharmacodynamic  PHARMACY A professional field and area of study which involves learning about pharmacology, and other subjects like drug formulation, medicinal chemistry, dispensing, and proper utilization of drugs.  BRANCHES OF PHARMACOLOGY Toxicology  Study of toxic effects of drugs (usually done on animals or cell cultures)  Also includes study of adverse effects Clinical Pharmacology  Study of drugs on humans (patients & healthy volunteers)  Efficacy, safety, compare to other drugs, adverse effects  TERMINOLOGY Pharmacokinetics – what the body does to the drug  Absorption  Distribution  Metabolism  Excretion Determines drug concentration in the body/circulation  TERMINOLOGY Pharmacodynamic – what the drug does to the body  Mechanism of action: bind to receptors (selective or not selective), inhibit enymes etc  Drug’s effects (pharmacological effects): therapeutic effects, side effects, adverse effects, toxic effects  Drug interactions: which cause an effect to the body  TERMINOLOGY Side effects  Unintended effect occurring at normal dose related to the pharmacological properties  Associated with dose  Eg warfarin – anticoagulant. Side effects: excessive bleeding  Eg propranolol (beta blocker) – reduce heart rate. Side effect: bradycardia  TERMINOLOGY Adverse reaction  A response to a drug which is harmful or unpleasant and unintended, and which occurs at doses normally used in man  Can be either dose-related, non dose-related, or time-related  Eg warfarin – anticoagulant. Adverse reaction: excessive (severe) bleeding (dose-related)  Eg antibiotic. Adverse reaction: hypersensitivity (non dose-related)  Eg steroid. Adverse reaction: diabetes, osteoporosis (time-related)  Tolerance TERMINOLOGY  Subject’s reaction to a drug decreases after prolonged exposure to the drug  Developed gradually after days or weeks  Thus required a larger dose to get the same effects. Eg opioids as pain killer: the pain killer effects diminished after a certain period, and larger dose is needed to obtain the same effects. Tachyphylaxis  sudden onset of tolerance (sudden decrease in response to a drug after repeated administration within short intervals)  Occurs within minutes Eg local anesthetic (administered via epidural) , repeated injection leads to reduce effectiveness.  TERMINOLOGY Drug resistance  Loss of effectiveness of antimicrobial or antitumour drugs.  USES OF DRUGS Diagnosis of disease - barium sulfate (radiocontrast images seen with x-ray) Treatment  Tx symptom eg paracetamol for headache  Specific tx – penicillin for streptococcal infection Prevention (prophylaxis) – eg vaccine, antimalarial agent To change physiological function – contraceptive pills NOMENCLATURE OF DRUGS Generic name/non-proprietary name  officially approved  Kept uniform by a specific body  Used in medical / scientific communications, medical books  Some older drugs have more than one name Eg paracetamol / acetaminophen Meperidine/pethidine Lignocaine/lidocaine Chemical name  describes the substance chemically  Not suitable for prescribing eg 1- (Isopropylamino)-3-(1-naphtylloxy)propan-2-ol for propranolol NOMENCLATURE OF DRUGS Commercial name(proprietary/trade/brand name)  Name assigned by manufacturer  One drug may have multiple commercial names eg drug atenolol, brand name Altol, Tenolol  Catchy, short, easy to remember, suggestive of its clinical use eg Lopresor  Brand names may differ in different countries Street name  slang names for street drugs  Street drugs - Legal substance but sold without prescription  or illegal substance. Not used for medical purposes NOMENCLATURE OF DRUGS Generic name/non-proprietary name  Eg paracetamol / acetaminophen Chemical name : eg N-Acetyl-p-aminophenol Commercial name(proprietary/trade/brand name) - Panadol® (GlaxoSmithKline), Tylenol® (American co), Uphamol® (Upha corporation), etc Street name – not applicable NOMENCLATURE OF DRUGS Generic name/non-proprietary name  Morphine Chemical name : eg (5 alpha, 6 alpha) 7,8 didehydro-4,5 epoxy-17methylmorphinan- 3,5diol. Commercial name(proprietary/trade/brand name) - Avinza®, Oramorph® Street name – Pok Teh, ‘M’ NOMENCLATURE OF DRUGS Viagra 1-{[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl- 1H-pyrazolo [4,3-d]pyrimidin-5-yl)-4- ethoxyphenyl]sulfonyl}-4-methylpiperazine citrate Sildenafil citrate Poke, Ubat kuat  DRUG CLASSIFICATION Mechanism of action  Beta-blockers eg propranolol, alpha-blockers eg prazosin Chemical structure  Catecholamines eg adrenaline Pharmacological effect  CNSstimulant eg amphetamine, CNS depressants eg alcohol, sedatives eg benzodiazepines Pharmacokinetics  Short acting, slow release  DRUG CLASSIFICATION Therapeutic uses  Antidiabetics, antihypertensives Chemotherapeutic  Antiprotozoal, antimycobacterial, antifungal, antiviral Natural source  Opioids: seeds of opium poppy (Papaver somniferum)  Digitalis glycoside: from leaves of foxglove plant (Digitalis lanata)  DRUGS Prototype drug  An original of something  An early type or form that serves as the basis or standard for later stages of the thing.  Eg beta blockers: propranolol Prodrug  drug that is administered in an inactive (or significantly less active) form. Once administered, the prodrug is metabolised in vivo into an active metabolite.  Eg fosphenytoin metabolized to phenytoin.  DRUGS Prescription Drugs: These drugs are used under medical supervision and control because potential of misuse, drug abuse and practicing medicine without a license and without sufficient education. e.g. antibiotics, antipsychotics etc Non-Prescription Drugs: These drugs are considered safe and effective for use by the general public without advice from a health professional, can be bought over the counter (OTC ) e.g. vitamins, paracetamol etc.  DRUG FORMULATION Liquid (suspension, elixir, syrup, ointment) Tablet Capsule Suppository - A small plug of medication designed to melt at body temperature within a body cavity other than the mouth:  Eg rectal (anti pyrexia), vaginal (to induce labour) Powder Gas  ROUTES OF DRUG ADMINISTRATION Generally can be divided into 3:  Enteral (intestinal) Drugs administered via the gastrointestinal tract eg oral, buccal, sublingual, rectal  Parenteral (beyond intestinal) Drugs administered by routes other than gastrointestinal tract eg intravenous, intramuscular, subcutaneous, intraarterial, intrathecal, epidural, transdermal  Local (localized effect) Lungs (inhale), eye (drop), nose (intranasal), ear (drop), skin (cream), joint (intra-articular), vagina (gel/suppository)  FACTORS AFFECTING ROUTE OF CHOICE Property of the drug: solid/liquid/gas Site of action: localized or generalized Rate of absorption via different routes Effect of gastric juice and first pass metabolism Routine treatment or emergency Accuracy of dosage required Condition of patient: unconscious, vomiting  ENTERAL ORAL (po ~ per os) Advantages  Most common, safe, easy, does not require special equipment or sterilization Disadvantages  Subjected to first-pass metabolism, destruction by gastric acid, slow absorption, require cooperation from patient, some drugs are unpalatable Fist pass metabolism: drugs taken orally which is transported to liver and metabolized first before it enter the systemic circulation  ENTERAL SUBLINGUAL & BUCCAL Under tongue (sublingual), between inner cheek and gum (buccal) Drug diffuse into capillary network, directly enter systemic circulation Advantages  drug bypass liver, no first pass effect  not destroyed by GIT enzymes/acid  rapidly absorbed Disadvantages  Requires patient’s cooperation  Possibility being swallowed or spit out  ENTERAL RECTAL 50% of rectal drainage bypasses portal circulation  metabolism of drug by liver is minimized Advantages  not destroyed by GIT enzymes/acid  Useful if patient vomiting or drug induces vomiting when given orally, unconscious patients, kids Disadvantages  Unreliable absorption  Inconvenient and embarrassing  Irritation/inflammation of rectal mucosa can occur  PARENTERAL INTRAVENOUS Most common parenteral route Used for poorly absorbed drug Advantages  Avoids GIT, so no first-pass metabolism  Rapid effect (emergency use), amount of drug delivered can be controlled Disadvantages:  Risk of bacterial infection  Embolism (blood vessel blocked by foreign body), thrombophlebitis (inflammation of the blood vessel)  Can cause adverse effects – rapid delivery of high concentration of drug into plasma/tissue – so must control rate of infusion  Once administered, difficult to reverse/withdraw the drug  PARENTERAL INTRAMUSCULAR Injected into large skeletal muscle ie deltoid, triceps, gluteus maximus (eg vaccine) Aqueous solution - Fast absorptn Depot preparation – enables sustained release  Eg Depo Provera (contraceptive) – every 3 months Advantages  Avoids 1st pass effect Disadvantages  Pain, abscess, unreliable absorption (drug may precipitate in muscle)  PARENTERAL SUBCUTANEOUS Absorption slower than i.v & i.m Minimise risk of i.v route Avoids 1st pass effect Eg insulin, contraceptive implants (eg levonorgestrel – depot preparation) Patients can administer themselves (insulin) Disadvantages:  Not suitable for large volume  Pain or necrosis  PARENTERAL EPIDURAL Drugs administered into epidural space of spine Often used for anesthesia in obstetrics Drugs will not get to the brain INTRA-THECAL (INTRASPINAL) Injected into subarachnoid space of spine Suitable for treatment of disease in the CNS and for drugs that is prevented to enter the brain eg antibiotic  PARENTERAL INTRA-ARTERIAL Advantages and disadvantages similar to intravenous, complication more severe More difficult since the arteries are located deeper Eg in angiography (inject contrast media) Common arterial sites eg femoral artery, radial artery  PARENTERAL INTRA-VENTRICULAR Injected directly into ventricle of the brain. Eg anticancer drugs  PARENTERAL TRANSDERMAL Patch Allows constant drug delivery for a certain period of time Eg analgesic (to relieve pain), nicotine patch Advantages: convenient Disadvantages: erythema  TOPICAL Applied directly to skin surface OR Administration to any mucous membrane eg eye, nose, ears, lungs, vagina Advantages: bypass first pass metabolism, allow localized effects, minimize systemic effects (less side effects) Eg cream (dermatitis), inhalation (asthma), eye drop (conjunctivitis), ear drop (otitis externa), intranasal (decongestant nasal spray), vaginal suppository (labour induction), intra-articular (arthritis)  NOTE: Inhalation Gas (general anaesthetic agent) – for systemic effects Aerosol (antiasthmatic agent) – for localized effects in the respiratory tract Intranasal Sniff/Snort eg cocaine - Rapidly reach the brain, bypass first pass metabolism (cause systemic effects)  REFERENCE BOOKS 1.Katzung, Basic & Clinical Pharmacology, 15th edition  Recommended, well balanced, up to date 2. Goodman & Gilman’s 14th ed The pharmacological basis of therapeutics  CONTACT US 1. Face-to-face (17th floor) 2. Individual email 3. Others: Facebook 4. Folio for announcements, lecture notes and SLP.