Pharmacology for Nursing PDF

Pharmacology for Nursing By Dr. Abeer M.R. Hussein What is Pharmacology? - Pharmacology is the drug science. - This includes knowledge about the mechanism of action, pharmacological effects, therapeutic uses, adverse effects and any other information about the drug. What is...

Pharmacology for Nursing By Dr. Abeer M.R. Hussein What is Pharmacology? - Pharmacology is the drug science. - This includes knowledge about the mechanism of action, pharmacological effects, therapeutic uses, adverse effects and any other information about the drug. What is general pharmacology? General pharmacology includes pharmacokinetics and pharmacodynamics: a) Pharmacokinetics - Pharmacokinetics deals with the processes that undergo to the drug following its administration. - These processes include: absorption of the drug, its distribution as well as its elimination (biotransformation and excretion). b) Pharmacodynamics - It deals with the action of a drug on the body, including receptor interactions, dose-response relationship, and mechanisms of therapeutic and toxic actions. What is the drug? Drug is a chemical substance used for prevention, diagnosis and treatment of diseases A. Drug absorption -It is defined by the transfer of a drug from its site of administration to the blood stream. -Drug absorption occurs by one of the following mechanisms: 1-Passive or lipid diffusion: -It occurs with the lipid soluble drugs. 2-Filtration or aqueous diffusion: -It occurs with water soluble drugs, where drugs pass through aqueous channels or pores between the cells. -These pores are absent in the blood brain barrier (BBB) and placental barrier, so any water soluble drug cannot cross BBB and placental barrier 3-Active transport: -It needs energy and carrier, so there are selectivity, saturability and competition. 4-Pinocytosis (endocytosis): -It occurs with high molecular weight drugs as iron, hormones and vit.B12.  Factors affecting drug absorption (a) Factors related to the drug: -Lipid solubility -Ionization -Molecular weight -Dosage form -Concentration  (b) Factors related to the patient: -Route of administration -Blood supply -Healthy state -GIT motility -Presence of other drugs -Presence of food Routes of Drug administration Classification: a) Enteral routes (related to GIT) Oral, sublingual and rectal b) Parenteral routes (away from GIT) Injections, local (topical) and inhalation (1) Oral route: * Advantages: -Safe -Economic -Easy * Disadvantages: -Delayed onset of action, so not suitable in emergencies. -Formation of complexes with foods as tetracyclines. -Destruction of drugs by HCI (as penicillins) or digestive enzymes (as insulin) -Inactivation by the liver as lidocaine. -Not suitable in unconscious, uncooperative, severely ill patients, and in presence of vomiting. Dosage forms used orally: 1-Oral drops 2-Syrup 3-Suspension 4-Capsuls 5- Tablets 6-Effervescent sachets Special types of tablets: -Enteric coated tablet -Sustained release tablet (SR) -Colored tablet -Effervescent tablet -Chewing tablet -Lozenges Enteric-coated tablets: tablets containing an outside layer that resists dissolution in the stomach and dissolves in the intestine. Advantages of enteric-coated tablets: a) devoid stomach irritation by irritant drug. b) devoid destruction of drug by gastric acid fluid c) mask bitter taste. Sustained release tablet (SR): tablets designed to be released and absorbed in stages over prolonged time to give long duration of action. (2) Sublingual route: * Advantages: - Rapid onset, so suitable in emergency as in angina, and severe hypertension. - By -pass first pass metabolism in the liver, * Disadvantages: - Not suitable for all drugs, only for nitrate (3) Rectal route: * Advantages: -Suitable in unconscious patient, in presence of vomiting. -50% of the drug by-pass liver as blood supply of the lower half of rectum passes to systemic circulation. -Can give local effect in the rectum or absorbed for systemic effect. * Disadvantages -Not suitable in diarrhea and may cause irritation. Dosage forms used rectally: 1-Suppository, used for both topical and systemic effects. 2-Enema (Evacuant or Retention) (4) Injections: (a) Intravenous (IV): * Advantages: -Very rapid onset, so suitable in emergency. -Proper dose adjustment. -Maintenance of drug in active form as no destruction in liver or by HCl, or digestive enzymes. -Suitable for large volumes (as fluids, blood). -Suitable for irritant drugs (as blood vessels are relatively insensitive). -Suitable in unconscious, uncooperative patients, severely ill patients, and in presence of vomiting. * Disadvantages: -More expensive, need aseptic condition, no self-medication, painful, and need patent vein. -Difficult to eliminate the drug if toxicity occurs. -Not suitable for suspension and oily solutions (as may form emboli). (b) Intramuscular (I.M.): * Advantages: -As IV (but IM is suitable only for moderate volume drugs, and in cases of irritant drug need deep IM injection), but unlike IV, it is suitable for suspension and oily solutions. * Disadvantages: -As IV (but IM is suitable in suspension, oily solutions), but unlike IV, it is not suitable for anticoagulant as heparin (as may cause hematoma). -Limited volume is given I.M. (4-5 ml). (c) Subcutaneous (S.C.): -Suitable for suspension, oily solutions, and gives prolonged duration of action. -Can be used with insulin, implantable contraceptive (S.C. pellets give effect for 5-6 years). -Disadvantages: slow onset, not suitable for large volume and irritant drugs (as cause severe pain, necrosis). -Absorption after S.C. (or IM) can be enhanced by increasing blood supply by massage, and hot fomentation and can be decreased by decreasing blood supply by cold fomentation, or injection of vasoconstrictor as EP. (d) Intrathecal: - There is high concentration in CSF, can be used in CNS infection to inject antibiotic, or in spinal anesthesia. - Also, can be used in diagnosis of some CNS disorders by withdrawing CSF samples. -Need special precaution to avoid infection, and nerve injury. Dosage forms used by injections: i. Ampules (for single dose). ii. Vials (for multidoses). (5) Inhalational route: -Suitable for volatile compounds, gases, and aerosol. -This route can be used for local or systemic effect. -Rapid onset due to large area of absorption. -Self-administration is possible. -Disadvantages: not used in irritant drugs, , difficult to adjust dose, and may need special apparatus. (6) Topical or local administration: -We apply drugs to skin or mucus membrane (of nose, throat, ear, conjunctiva, rectum, or vagina). -Provides high local concentrations with little or no systemic effects (but some drugs used topical to give systemic effect as in transdermal patch of angina). -Disadvantages: some systemic absorption may occur especially in presence of destruction or inflammation of skin and if the drug is highly lipid soluble as in organophosphorus compounds. Dosage forms used locally: 1-Drops (eye, nasal, and ear drops) 2-Ointment (applied for dry skin). 3-Cream (applied for wet skin). 4-Lotion 5-Transdermal patch Nursing implication: When the solution administered intravenously, it must be sterile, aqueous, and free of particulate matter. So, turbid solution should never be administered I.V. Suspensions should never be administered intravenously. All suspensions should be shaken immediately just prior to administration in order to assure dosage uniformity. Sustained release tablet should not be crushed.