Dosage forms of drugs

Objectives: - Know the chemical structure of drugs - Know the nomenclature of drugs - Identify the major sources of drugs - Describe different dosage forms - Understand properties of each dosage form - Specify advantages/disadvantages of each dosage form type

Chemical nature of drugs - Acidic; Aspirin, barbiturates...etc - Basic or alkaline; Morphine, Atropine, Alkaloids...etc - Neutral; Steroids...etc

Sources of drugs: - Natural Plants (atropine, digoxin), animals (insulin), human (growth hormone; hMG; hCG) - Semisynthetic (human insulin) - Synthetic (agonists; antagonists)

Nomenclature of drug : - Chemical name e.g. acetyl salicylic acid - Generic name; nonproprietary; official; approved name... Aspirin (most widely used in pharmacology) - Official name... Aspirin BP; Aspirin USP - Trade name; Proprietary; brand name Remine®; Bufferin®...etc

Dosage forms Dosage form is the crude drug in its final (active) form after adding particular characteristics to it (additives) to make it easily taken by patients Additives may include thickeners, stabilizers, preservatives, coloring agents, flavoring agents...etc

- Thickeners:  To harden/thicken creams and ointments - Stabilizers: To maintain the stability of a drug - Preservatives: To protect the drug from contamination by microorganisms such as bacteria and fungi - Coloring agents: To give the drug a perfect appearance and attractiveness - Flavoring agents: To hide a bad taste like the bitter taste and increase its palatability

Importance of dosage forms: - To ensure administration of an accurate dose - To protect patient from gastric or GI irritation - To have optimal action of the drug (Sustained or controlled release) - To mask unpalatable taste or unpleasant odor - To provide stability to drugs against atmospheric conditions ** Before approval of FDA the manufacturer company must clearly state in what dosage form or forms the drug will be manufactured

Dosage forms could be classified according to: 1. Route of administration: -Topical or local Creams, ointments, suppositories, vaginal tablets, powder for inhalation, ophthalmic drops, intranasal drops, ear drops...etc - Oral Tablets and capsules (immediate, sustained or extended-release), solutions and suspensions, lozenges, inhaled aerosol powders or sprays...etc

- Parenteral Sterile solutions given by injection Intravenous (I.V.): in vein; Intramuscular (I.M.): in muscle; Subcutaneous: under the skin; Intraarterial: in artery; Intraarticular: in the joint; Intracardiac: in the heart; Intrathecal/Intraspinal: in the spine; Intraperitoneal: in the peritoneal membrane in the abdomen...etc

2. Physical properties of drugs: - Solid dosage forms - Semisolid dosage forms - Liquid dosage forms - Gaseous dosage forms

Solid dosage forms: - Tablets - Capsules - Modified release tablets & capsules - Chewable tablets - Lozenges - Effervescent tablets - Granules...

Tablets Powder compressed in flat or circular shape - Immediate release tablets; have spontaneous dissolution and absorption depends on the physicochemical properties of the drug - Sustained or slow or extended release tablets The release of drug is under the control of a delivery system

Delayed release tablets or capsules are designed to protect the active drug against destruction by gastric acid Extended release tablets or capsules are designed to release the active drug in a controlled manner at a specific rate, duration and location to achieve proper therapeutic concentration

Advantages of modified release forms: - Release active drug in slow or delayed or extended manner and thus avoid fluctuations of plasma drug concentration (improve peak-to-trough fluctuations) - Decreased frequency of drug administration (often once daily administration) - Associated with better compliance - Treatment can be cheaper

Capsules A cylindrical soluble container enclosing the drug Tow types: 1. Hard gelatin capsules (contain the dug which is in solid form=powder or granules) 2. Soft gelatin capsules (contain the drug which is in liquid or semisolid forms)

Advantages of tablets and capsules dosage forms: - Easy to administer - So much convenient to patients Disadvantages: - Difficult to be swallowed by children - Still some may cause GIT irritation

Chewable tablets Solid dosage form containing the active drug intended to be chewed Easily swallowed and have pleasant taste Lozenges Solid form composed of the active drug, sugar and gum to increase its hardness Have good taste and used for mouth and throat problems

Effervescent Tablets Tablets containing the drug, acids and sodium bicarbonate Need to be dissolved in water before administration Release carbon dioxide when dissolved in water

Caplets Tablets in capsule shape Granules Solid dosage forms designed to offer administration of large dose of a given drug

Semisolid dosage forms - Ointments - Creams - Gels - Suppositories - Aerosols - Transdermal Patches

Advantages of semisolid dosage forms: 1. Applied directly to skin or mucous membranes 2. Bypass systemic absorption 3. Have direct action 4. Easy to apply and not irritant 5. Safe and effective method of administering medications 6. Easily water washable

Disadvantages of semisolid dosage forms: 1. Poorly absorbed so not intended for systemic treatment 2. Still some drugs applied topically or locally may be absorbed to some degree that may cause adverse effects 3. Some drugs may be easily degraded by certain enzymes present in the skin leading to inactivation of the active drug

Liquid dosage forms (Solutions) A solution is a clear, homogeneous liquid dosage form that contains one or more chemical substances dissolved in a solvent or mixture of solvents (could be given orally or by injection) Advantages: - Easy to be administered (oral) - Fast dissolving drug delivery system, rapid absorption - Convenient to children and elderly

Disadvantages of liquid dosage forms: - Some drugs have poor solubility - Some liquid dosage forms are not palatable (have bitter taste) (oral) - Liquid dosage forms given by injection need expert and they are painful Types of solutions: Syrup A syrup is an oral solution that contains high concentrations of sucrose or other sugars and a flavoring agent

Elixir An elixir is a clear, pleasantly flavored, sweetened liquid containing alcohol and a dissolved drug. It is usually taken by mouth Suspension A suspension is a liquid dosage form that contains solid particles that are dispersed in a liquid vehicle. Important to always shake before use

Gaseous dosage forms A gas is any elastic aeriform fluid in which the molecules are separated from one another and able to move freely Best example is general anaesthetics and aerosols Advantages Easy to administer and to control the given dose (↑ or ↓) Disadvantages: May lead to irritation to the respiratory system