Pharmaceutical Drug Administration & Pharmacokinetics Defined

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Daymar College

Are you looking for a vocational program where you can learn to become a nurse? Ready to learn more about administering medicine to patients and what happens to the medicine once it is administered?

There are a few ways to administer medicine enterally, they include tablets and capsules, sublingual, buccal, nasogastric and gastrostomy methods. Medicine can be administered in a topical route through transdermal delivery, ophthalmic, otic, nasal, vaginal and rectal methods. Medicine can also be administered through parenteral routes including intradermal, subcutaneous, intramuscular, and intravenous methods.

Pharmacokinetics focuses on how drugs move within the body after administration. The movement of drugs includes absorption, distribution, metabolism and excretion. Another element of the drug lifecycle is the rate of elimination. The nurse will need to be familiar with drug administration, the movement of the drug in the body and the rate of elimination to properly diagnose and treat a patient.

Enteral Drug Administration

The enteral route includes drugs taken orally, nasogastric or gastrostomy tubes. This route is most common because it is the easiest and usually the least costly. It is also considered the safest route as the skin is not penetrated.

Tablets and Capsules – the most common form of drugs and the easiest to use by the patient. The stomach may destroy some medications, so a hard, waxy coating may be used to protect them from acidity. Sustained-release tablets are made to dissolve very slowly and can be used instead of multiple doses each day. The more doses a patient takes per day, the more likely they are to miss a dose. One disadvantage to oral administration is the patient that takes the tablets or capsules must be conscious.

Sublingual Route – the patient does not swallow the tablet, instead they keep the tablet in the mouth and let it dissolve. Typically, the medication is placed under the tongue and allowed to dissolve. There is a rich supply of blood under the tongue, so the drug enters the blood stream quickly and starts to work right away.

Buccal Route – the tablet, capsule, lozenge, or troche is placed in the mouth between the gum and the cheek. The patient is not to touch the medicine with the tongue, so it doesn’t get swallowed accidently. Medicine is absorbed slower from the buccal route rather than the sublingual route.

Nasogastric and Gastrostomy Administration – medicine is administered through soft, flexible nasogastric tubes inserted in the nasopharynx or oropharynx, with the end of the tube emptying in the stomach. Nasogastric tubes are typically used for short-term administration. Gastrostomy tubes are surgically placed into a patient’s stomach and used for long-term administration of liquid medicine.

Topical Drug Administration

The topical route involves applying drugs to the skin or membranous lining of the eye, ear, nose, respiratory tract, urinary tract, vagina and rectum. Drugs can be dermatologic preparations that are applied to the skin using formulations including creams, lotions, gels, powders and sprays. Instillations are drugs applied into the body cavities or orifices. Inhalation applies drugs by inhaler, nebulizer or positive-pressure breathing apparatuses. Some topical drugs are applied to give a local effect and others to give slow release and better absorption into the general circulation.

Transdermal Delivery System – transdermal patches administer drugs by being applied to the skin. A popular transdermal medicine is scopolamine for motion sickness.

Ophthalmic Administration – used to treat local conditions of the eye. Ophthalmic administration of drugs is done by eye irrigation, drops, ointments, and medicated disks.

Otic Administration – used to treat local conditions of the ear, including infections and blockage. Otic administration of drugs is done by eardrops and irrigations.

Nasal Administration – a trans-mucosal method of drug delivery used for local and systemic drug administration. Nasal administration offers an absorbent surface for medications to enter the blood stream.

Vaginal Administration – used to deliver medications for treating local infections and to relieve vaginal pain and itching. Vaginal medications are delivered as suppositories, creams, jellies or foams.

Rectal Administration – used for either local or systemic drug administration. An easy way to deliver medicine to patients that are comatose. Rectal drugs are usually given in suppository form.

Parenteral Administration

The parenteral route delivers drugs by needle into the patient’s skin layers, tissue, muscles or veins. The medical assistant that administers medicines through parenteral methods should know the correct anatomical locations for administration and proper safety procedures for disposal of hazardous equipment.

Intradermal Administration – used to deliver medicine to the blood vessels that supply the layers of skin. Intradermal injections are administered into the dermis layer of skin. Typically, this route is used for allergy and disease screening for local absorption in the blood vessels. Some of the disadvantages of intradermal administration is that only small amounts of medicine can be administered, and the patient may experience pain and swelling at the injection site. Intradermal injections are made at a 10 to 15-degree angle to the skin to administer medicine just under the epidermis.

Subcutaneous Administration – injects medicine to the deepest layers of the skin at a 45 to 90-degree angle into subcutaneous tissue, just under the dermis.

Intramuscular Administration – injection delivers medication into specific muscles at a 90-degree angle. Medicine injected into the muscle moves quickly into the blood vessels and produces a quick response. Injection sites must be located away from bones, large blood vessels, and nerves.

Intravenous Administration – enables administration of medicine and fluids directly into the bloodstream for the body to use immediately. Although the IV route is the fastest way to inject medicine it is also the most dangerous. Once injected, the medicine can’t be retrieved.

Pharmacokinetics

Pharmacokinetics focuses on how drugs move within the body once administered. The movement of drugs involves four processes which include absorption, distribution, metabolism, and excretion.

Absorption - The first step in how the body handles a drug. Absorption involves the movement of a substance from the location of administration across one or more body membranes. Drugs may be absorbed into the skin or the membranes that line blood vessels.

Distribution – the process of how the drugs are transported after they are absorbed or administered into the bloodstream. There are many factors that affect the movement of a drug from the injection site to the target tissue, they include:

  • Binding – occurs between drugs and other substances in the body. An example of this is plasma proteins that are present in the bloodstream and may bind with a drug stopping it from reaching the target tissue.
  • Bioavailability – describes how much of a drug will be available after injection to produce a biological effect. Important organs in the body contain anatomic barriers that prevents some portion of a drug from reaching the target tissue.
  • Blood-Brain Barrier – composed of high-density cells restricting passage of drugs from the bloodstream. This barrier is much more stringent to drugs than endothelial cells in capillaries of the body.
  • Blood-Placental Barrier – regulates which substances pass from the mother’s bloodstream to the fetus.
  • Blood-Testicular Barrier – the body has a natural barrier that prevents many drugs from reaching the testes.

Metabolism – the total of all chemical reactions in the body, that occurs in almost every cell and organ in the body. Age, kidney and liver disease, genetics and other factors can affect the metabolism.

Excretion – most substances that enter the body are removed by urination, exhalation, defecation or sweating. Drugs are removed from the body by the kidneys, the respiratory tract, bile or glandular activity.

  • Kidney Excretion - The kidney of the body removes all non-natural and harmful substances in the bloodstream.
  • Respiratory Excretion – excretes drugs that are easily changed into a gaseous form. The rate of respiratory excretion is dependent on diffusion, gas solubility, and blood flow.
  • Bile Excretion – components of bile are circulated back to the liver, this is called enterohepatic recirculation. Recirculation drugs are then metabolized by the liver and excreted by the kidneys.
  • Gland Excretion – drugs are excreted by the production of body fluids including saliva and perspiration.

Rate of Elimination

The amount of drug removed per unit of time from the body by normal body processes. The elimination rate is an indicator of how long a drug will produce its effect.

  • Half-Life – the length of time required for a drug’s concentration in the plasma to increase by one half. The larger the half-life the longer it takes for the drug to be eliminated.
  • Drug Potency - refers to a drug’s strength at a specific concentration or dose.
  • Drug Efficacy – the ability of a drug to produce a more intense response as its concentration is increased.

Interested in learning more about administration of drugs to patients as a nurse? Ready to learn about pharmacokinetics and the rate of drug elimination in the body? As a successful graduate with a nursing degree, you may be prepared to work as a beginning professional nurse in hospitals, physicians' offices, nursing and residential facilities, and home health care centers. If you're interested in pursuing a nursing degree, we have the degree program for you. Daymar College’s Associate of Science degree in Nursing is designed to provide the foundation for beginning the practice of professional nursing.