Use of drugs and precaution in veterinary practise

Dr C Lalmuanthanga
In English, the noun “drug” is thought to originate from Old French “drogue”, possibly deriving from “droge (vate)” from Middle Dutch meaning “dry (barrels)”, referring to medicinal plants preserved as dry matter in barrels.
A drug is any substance that causes a change in an organism’s physiology or psychology when consumed.
In pharmacology, a drug is a chemical substance, typically of known structure, which, when administered to a living organism, produces a biological effect. A pharmaceutical drug, also called a medication or medicine, is a chemical substance used to treat, cure, prevent, or diagnose a disease or to promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders.
Drugs are used for different purposes viz. medication, spiritual and religious use, smart drugs and designer drugs and recreational use.
1) Medication : A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition as a prophylactic or therapeutic.
2) Spiritual and religious use : Some religions, particularly ethnic religions are based completely on the use of certain drugs, known as entheogens, which are mostly hallucinogens, - psychedelics, dissociative, or deliriants.
3) Smart drugs and designer drugs: Nootropics, also commonly referred to as “smart drugs”, are drugs that are claimed to improve human cognitive abilities. Other drugs known as designer drugs are produced e.g. LSD
4). Recreational drug use: Some recreational drugs that are legal and accepted in many places include alcohol, tobacco, betel nut, and caffeine products, and in some areas of the world the legal use of drugs such as khat is common.
i) Drugs Acting on Digestive System,  Example: Antacid, Purgative, Antiulcer
ii) Drugs Acting on Respiratory System, Examples: Diuretics, Antidiuretics, Antiseptic, Urinary acidifier, Urinary alkalizer.
iii) Drugs Acting on Urinary System, Examples: Bronchodilator, Antitussive, Expectorants, Decongestants.
iv) Drugs Acting on Reproductive System,  Examples: Oxytocin, Tocolytics, Abortifacients.
v) Drugs Acting on Heart and Circulatory system, Examples: Cardiac stimulants, Cardiac tonics, Antiarrhythmic drugs, Vasoconstrictor, Vasodilators, Anticoagulants.
vi) Drugs Acting on Nervous System, Examples: Cerebral stimulants, Cerebral depressants, Antipsychotics,  Antidepressants etc.
vii) Drugs Acting on Autonomic Nervous System/Peripheral Nervous System, Examples : Parasympathomimetric, Parasympatholytic, Sympathomimetics, Sympatholytic.
viii) Drugs Acting on the Eye, Examples: Mydriatics, Miotics.
ix) Drugs Acting on the Skin and Mucous Membranes, Examples: Counter-irritants, Haemostatic, Detergents, Keratolytic.
x) Chemotherapeutic Agents, Examples: Antibiotic, Antiseptics, Anthelmintics.
Drugs Given by Mouth:
Oral dosage forms (given by mouth) include liquids (solutions, suspensions and emulsions), semi-solids (pastes), and solids (tablets, capsules, powders, granules, premixes and medicated blocks).
Drugs Given as Injections or Implants:
A drug that is given parenterally – that is, by injection or as an implant – does not go through the gastrointestinal system. These drugs may be formulated in several different ways for use in animals, including solutions, suspensions, emulsions, and as a dry powder that is mixed with a liquid to become a solution or a suspension immediately prior to injection. Dry powders are used for those drugs that are unstable in liquid form.
The majority of implants used in veterinary medicine are compressed tablets or dispersed matrix systems in which the drug is uniformly dispersed within a non-degradable polymer.
Drugs Applied to the Skin or Mucous Membranes:
The dosage forms applied to the skin or mucous membranes that are available for treating animals include solids (dusting powders), semi-solids (creams, ointments, and pastes) and liquids (solutions, suspension concentrates, and emulsifiable concentrates). These are known as topical drugs. Of special interest are transdermal delivery systems that work by carrying medications across the skin barrier to the bloodstream. Examples of these are transdermal gels and patches that are used in pets. There are also dosage forms that are unique to veterinary medicine, such as spot-on or pour-on formulations developed for the control of parasites.
Different drugs are administered in the animals through various routes. There are different dosage formulations and delivery systems that are used to provide for the care and welfare of animals. But the most important is use of the drug at the correct dosage for effectiveness and safety. In animal, use of drug can be complicated because of the variety of species and breeds treated the wide range in body sizes, different animal rearing practices, seasonal variations, and the level of convenience, among other factors. Broadly, routes of  drug administration may be classified as:
1. Enteral routes of administration: (i) Oral (per os or PO) (ii) Sublingual (iii) Rectal administration
2. Parenteral routes of administration: Most commonly employed parenteral routes are as follows – (i) Intravenous (I/V; i.v.) (ii) Intraperitoneal (I/P or i.p.) (iii) Intramuscular (I/M or i.m.) (iv) Subcutaneous (S/C or s.c.)
3. Topical applications/Epicutaneous routes.
Paracelsus stated that everything is poisonous depending on the dose. Hence, use of drug must be done with precaution and it should be used judiciously. Some of the important points to be noted when using drugs are;
1. Use only the drug that is prescribed by the registered veterinarian only. Do not try to prescribe or suggest what drugs to be given to the animals if you are not entitled.
2. Check the label of the drug properly: The name of the drug should be properly checked before use and the composition and recommended route of administration should be checked before used to avoid any mistake.
3. Give the drug to animals as per the intended formulation and delivery system.
4. Always observe the withdrawal period  when using the drugs in food producing animals.
5. Avoid unnecessary use of drugs. Treating unknown fever, which may be due to virus, with antibiotics may lead to the development of microbial resistance organism.
6. Check the expiry of the drugs carefully. Otherwise, used of expired drugs may cause harm to the animals.
7. Perform hand hygiene. Whenever the drugs are to be administered into the animals, always observe good hygiene practice.
8. Do not combine the drugs that are incompatible. Wrong combination of two or more drugs in vitro or in vivo may results into production of  ineffective drugs or unwanted effects of drugs.
9. You must know the mechanism of action and toxicity of those drugs that you are using.
10. Extra label use of drug should be done only under special circumstances as permissible by FDA only.
11. You must aware about interaction of drug to be used with other substances such as food, chemical and other drugs.
12. Dose and dosage regimen of drug should be strictly followed. Too little or too large dose should be avoided. The dosage regimen should be properly followed to avoid drug resistance or toxicity.
13. Different factors such as physiological factor, genetic factor, pathological factor, environmental factor and therapeutic factor should be considered before using drug as they can influence the drug dosage and drug effect.
The writre is Assistant Professor, Department of Pharmacology & Toxicology, College of Veterinary Sciences & A.H., CAU (I) Selesih, Aizawl