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Definitions, drug nomenclature, and sources of drugs:

2 1 Definitions, drug nomenclature, and sources of drugs 1.1 DEFINITIONS Definitions Pharmacology – Deals with effects of drugs on living system Drug – Any substance or product that is used or intended to be used to modify or explore physiological system or pathological states for the benefit of recipient (WHO) Pharmacokinetics Movement of drug within the body Includes process of absorption (A), distribution (D), metabolism (M), and excretion (E) Means “what the body does to the drug” Pharmacodynamics Study of drugs, their mechanism of action, pharmacological actions, and their adverse effects Means “what drug does to body” Pharmacy Science that deals with preparation, preservation, standardization, compounding, dispensing and proper utilization of drugs Therapeutics Concerned with treatment of diseases Toxicology Study of poisons, their actions, detection, prevention and treatment of poisoning Chemotherapy Deals with treatment of infectious diseases/cancer Clinical pharmacology Study of drug in man, both healthy volunteers and patients, by comparative clinical trials Essential drugs Satisfy the health care needs of majority of population Should be available at all times, in adequate amounts, and in appropriate dosage forms (WHO) Orphan drug Used for diagnosis, treatment or prevention of rare diseases K395281_C001.indd 2 10-9-19 7:45:39 AM K395281_C002.indd 1


Definitions, drug nomenclature, and sources of drugs 3 1.2 DRUG NOMENCLATURE 1.3 SOURCES OF DRUGS Drug nomenclature Chemical name e.g. Acetylsalicylic acid Not suitable for use in prescription Non-proprietary name e.g. Aspirin Also called as generic name Same worldwide Assigned by U.S. Adopted Name (USAN) council Proprietary name e.g. Dispirin Also called brand name Given by pharmaceutical manufacturers A drug may have many brand names Sources of drugs 1. Natural a. Plants i. Alkaloids – morphine, atropine, quinine ii. Glycosides – digoxin, digitoxin b. Animals Insulin, thyroxine c. Minerals Ferrous sulfate, magnesium sulfate d. Microorganisms Penicillin, streptomycin e. Genetic engineering (recombinant DNAtechnology) Human insulin, hepatitis B vaccine 2. Synthetic: Aspirin, paracetamol K395281_C001.indd 3 10-9-19 7:45:39 AM K395281_C002.indd 2


4 2 Routes of drug administration 2.1 FACTORS DETERMINING ROUTES OF DRUG ADMINISTRATION Drug characteristics Type of use – eme r gency / routin e Patient condition – unconscious, vomiting, diarrhea Factors determining route of administration Age Co-morbid diseases Patient/doctor choice K395281_C002.indd 4 10-9-19 11:56:44 AM K395281_C002.indd 3


Routes of drug administration 5 2.2 LOCAL ROUTE 2. Deeper areas are reached by using syringe and needle e.g. Infiltration of local anesthesia Local route One of simplest route Given at site of desired action Minimal side effects 1. Topical Drug applied to skin/mucous membrane for local actions a. Oral cavity e.g. Clotrimazole troche for oral conditions b. GIT As non-absorbable tablet e.g. Neomycin for gut sterilization before surgery c. Rectum and anal canal Liquid drug is administered in rectum As evacuant enema for bowel evacuation e.g. Soap water enema; soap acts as lubricant and water stimulates the rectum Retention enema e.g. Methylpredinisolone in ulcerative colitis Suppository Solid dosage form drug is inserted in rectum e.g. Bisacodyl for bowel evacuation d. Eye, ear, and nose As drops, ointments, sprays, etc. For allergic or infective conditions of eye, ear, and nose e. Bronchi As inhalation e.g. Salbutamol inhalation for bronchial asthma, and COPD (chronic obstructive pulmonary disease) f. Vagina As tablet, cream, pessary For vaginal candidiasis g. Urethra As jelly e.g. Lignocaine K395281_C002.indd 5 10-9-19 11:56:44 AM K395281_C002.indd 4


6 Pharmacology mind maps for medical students and allied health professionals 2.3 SYSTEMIC ROUTE ( C o nt i n u e d ) Systemic route Drug reaches blood and produces systemic effects i.e. Enteral route Oral, sublingual, and rectal route 1. Oral route Most common and accepted e.g. Tablets, capsules, syrups, etc. Advantages Safe Cheap Painless Convenient for repeat and long-term use Self-administered Disadvantages Slow onset, not used in emergency Unpalatable, highly irritant drugs cannot be given Unabsorbable drugs cannot be given (e.g. neomycin) Drugs destroyed by digestive juices cannot be given (e.g. insulin) Drugs with high first-pass metabolism cannot be given (e.g. lignocaine) Cannot be given in unconscious/ uncooperative/unreliable patients Cannot be given in patients with vomiting or diarrhea Enteric-coating of tablets Prevents gastric irritation Protects drug from gastric acid Retards drug absorption and  its duration of action Done by cellulose, acetate, etc. Sustained/controlled release formulation Consists of different coatings dissolving at different time intervals  Duration of action  Dosing frequency  Patient compliance e.g. Sustained-release nifedipine K395281_C002.indd 6 10-9-19 11:56:45 AM


Routes of drug administration 7 2. Sublingual route Drug is kept under tongue Absorbed through the buccal mucosa Enters systemic circulation Bypasses first-pass liver metabolism Rapid onset e.g. Nitroglycerin, buprenorphine Action can be terminated by spitting out drug Disadvantages Advantages Bypasses first-pass liver metabolism Self-administration is possible Irritant and lipid- insoluble drugs cannot be given Unpalatable drugs with bad smell cannot be given Cannot be used in children 3. Rectal route Solids and liquid dosage forms used i. Enema For local effect i.e. Retention enema e.g. Methylprednisolone Evacuant enema e.g. Soapy water For systemic effect e.g. Diazepam for febrile convulsions in children 2.3 SYSTEMIC ROUTE (Continued) ( C o nt i n u e d ) K395281_C002.indd 7 10-9-19 11:56:45 AM


8 Pharmacology mind maps for medical students and allied health professionals B. Parenteral route Administered other than enteral route Injection, inhalation, and transdermal route Advantages Rapid onset, and can be used in emergency Also be used in unconscious/unco- operative/unreliable patients Used in presence of vomiting and diarrhea Suitable for irritant drugs Drugs with high first-pass metabolism can be given by this route Drugs that are not absorbed orally also can be given Drugs destroyed by digestive juices can be administerd by this route Disadvantages Require sterilization and aseptic conditions Invasive technique, painful Can cause local tissue injury; e.g. nerves, vessels, etc. Requires technical experts, hence cannot be self-administered Expensive 2.3 SYSTEMIC ROUTE (Continued) ( C o nt i n u e d ) K395281_C002.indd 8 10-9-19 11:56:45 AM


Routes of drug administration 9 1. Inhalation Volatile liquids and gases are administered by this route e.g. General anesthetics Advantages Rapid onset Lower dose is required, fewer systemic side effects Dose regulation is possible Disadvantages Local irritation can cause T respiratory secretions and bronchospasm 2. Transdermal route (adhesive patches) Patches deliver drug into circulation for systemic effects e.g. Scopolamine for motion sickness Nitroglycerin for angina Estrogen for hormone replacement therapy (HRT) Fentanyl for analgesia Advantages Self-administered Good patient compliance Prolonged action Minimal side effects Constant plasma concentration Disadvantages Expensive Local irritation (itching, dermatitis) Patch may fall off without being noticed 2.3 SYSTEMIC ROUTE (Continued) ( C o nt i n u e d ) K395281_C002.indd 9 10-9-19 11:56:45 AM


10 Pharmacology mind maps for medical students and allied health professionals 3. Injection a. Intradermal Injected into dermal layer of skin e.g. BCG vaccination, drug sensitivity testing b. Subcutaneous Injected into subcutaneous tissue e.g. Insulin, adrenaline Advantages Self-administered; e.g. insulin Depot preparations can be used; e.g. norplant for contraception Disadvantages Unsuitable for irritant drugs Slow onset, unsuitable for emergency c. Intramuscular Injected into large muscles Deltoid, gluteus maximum, lateral aspect of thigh in children Advantages Rapid onset compared to oral route Depot preparations (used to prolong drug action), mild irritants, soluble substances and suspensions can be given Disadvantages Requires aseptic condition Painful, may lead to abscess Self-administration is not possible Local tissue injury can occur; e.g. nerves 2.3 SYSTEMIC ROUTE (Continued) ( C o nt i n u e d ) K395281_C002.indd 10 10-9-19 11:56:45 AM


Routes of drug administration 11 d. Intravenous Direct injection of drug into vein Bolus administration – single, large dose rapidly/slowly injected as single unit e.g. Furosemide Slow IV injection e.g. Morphine IV infusion – addition of drug into a bottle containing dextrose/saline e.g. Dopamine infusion in cardiogenic shock Advantages 100% bioavailability Rapid onset, suitable for emergencies Large volume of fluid can be given (IV dextrose) Highly irritant drugs can be given (e.g. anticancer drugs) Hypertonic solutions can be given (20% mannitol) Constant plasma levels can be maintained (dopamine in cardiogenic shock) Disadvantages Once drug is injected, drugs action cannot be stopped Local irritation, thrombophlebitis Strict aseptic conditions are mandatory Caution Self-administration is not possible Drug extravasation cause necrosis, slougting Depot preparations cannot be given Administer drugs slowly, otherwise toxicity Ensure tip of needle is in vein 2.3 SYSTEMIC ROUTE (Continued) ( C o nt i n u e d ) K395281_C002.indd 11 10-9-19 11:56:46 AM


12 Pharmacology mind maps for medical students and allied health professionals 2.4 SPECIALIZED DRUG DELIVERY f. Intra-thecal Injection of drug in subarachnoid space e.g. Spinal anesthesia (lignocaine), antibiotics (in meningitis) e. Intra-arterial Rarely used now Used diagnostically e.g. Coronary angiography Sometimes anticancer drugs can be given g. Intra-articular Direct injection of drug into joint space e.g. Hydrocortisone for rheumatoid arthritis Requires strict aseptic condition Repeated use can damage cartilage 2.3 SYSTEMIC ROUTE (Continued) C. Specialized drug delivery 1. Ocusert Kept beneath lower eyelid e.g. Pilocarpine in glaucoma Single application releases drug for 1 wk 2. Progestasert Intrauterine contraceptive device Releases progesterone for 1 yr 3. Liposomes Drug incorporated in minute phospholipid vesicles e.g. Liposomal amphotericin for fungal infection 4. Monoclonal antibiotics Immunoglobulins react with specific antigen Used for targeted delivery e.g. Anticancer drugs K395281_C002.indd 12 10-9-19 11:56:46 AM

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