LESSON 2. Basics of Pharmacology

8/10/2019 LESSON 2. Basics of Pharmacology

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LESSON 2. Pharmacology Basics

Drugs Names

CHEMICAL NAME

identifies chemical elements and compounds that are found in the drug.

is important to chemists, pharmacists, and researchers who work with drugs at the chemical level. looks strange to anyone who isnt a chemist and is difficult for most of us to pronounce. Thats why names other than the

chemical name are given to a drug.

Example of chemical name for a commonly used drug: N-acetyl-p-aminophenol.GENERIC NAME

the universally accepted name and considered the official proprietary name for the drug.

appears on all drug labels and is the official name listed in official sources such as the Physicians Desk Reference (PDR).

The pharmaceutical company that patents a drug has exclusive rights to sell it until the patent expires.

When the patent expires, other drug manufacturers may distribute the drug under the drugs generic name or create a brandname.

The generic version of a drug may be cheaper than the original drug and the cost is usually reimbursed by insurance companies.

An example : acetaminophen

The generic name is easier to read and pronounce than the drugs chemical name, N -acetyl-p-aminophenol.BRAND/TRADE NAME

Drug companies often select and copyright a trade or brand name for their drug.

This restricts the use of this name to that particular company.

Many brand names may exist for the same chemical compound.

Brand name drugs may be more costly than generic drugs and are partially reimbursed or not covered at all by insurancecompanies.

example brand name for acetaminophen is Tylenol (patented by Johnson & Johnson Pharmaceuticals).

Prescription versus Over-the-Counter Drugs

Drugs that fall under Prescription drugs are:

Those given by injection.

Hypnotic drugs (drugs that depress the nervous system).

Narcotics (drugs that relieve pain, dull the senses and induce sleep).

Habit-forming drugs.

Drugs that are unsafe unless administered under the supervision of a licensed practitioner.

New drugs that are still being investigated and not considered safe for indiscriminate use by the public.

Non-prescription drugs

called over-the-counter (OTC) drugs and are available to the public without prescription.

Some over-the-counter drugs were at one time available by prescription, but later were considered safe for use by the public orreformulated for over-the-counter use.

Some drugs can be sold in lower doses over-the-counter (OTC) while higher doses of the same drug require a prescription as

per FDA requirements

Drug Safety

Drugs must undergo rigorous testing before being approved by the Food and Drug Administration for use in humans.

The initial testing is done with animals to determine the toxicity of the drug.

Acute toxicityis the dose that is lethal or kills 50% of the laboratory animals tested.o The testing is also done to determine what symptoms are experienced by the animals and the time the symptoms appear

Subchronic toxicity studies, conducted in at least two animal species, usually consist of daily administration of the drug for up to 90days.

o Physical examinations and laboratory tests are performed throughout the study and at the end of the study to see whatorgans may have been adversely affected by the drug

Chronic toxicity studies, also conducted in at least two species, usually last the lifetime of the animal but the length of the study maydepend on the intended duration of drug administration to humans.o Three dose levels are used, varying from a nontoxic low-level dose to a dose that is higher than the expected therapeutic

dose and is toxic when given over a long period of time.o Physical examinations and laboratory tests are performed to determine which organs are affected and whether the drug has

the potential to cause cancer (carcinogenic).

Animal studies enable scientists to develop a therapeutic index for the drug.o A therapeutic index is the ratio between the median lethal dose and the median effective dose.o It tells a practitioner the safe dose to give for the therapeutic effect to be achieved.o Some drugs have a narrow margin of safety and require that the blood plasma levels be frequently monitored to assure that

the drug stays within the therapeutic range.


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o Drugs that have a wide margin of safety dont require that the plasma levels be monitored.o Digitalis (digoxin) is an example of a drug that has a narrow margin of safety and requires frequent monitoring of plasma

levels.

Scientists also learn how the drug is absorbed, distributed, metabolized, and excreted once it is administered to the animals.o This helps scientists predict how the drug will react when administered to humans

Tests are also conducted in laboratory test tubes that can determine the metabolism of the drug in humans, which may be differentfrom animals.

o These are called in vitro studies.

o

Once animal studies are successfully completed, the drug is ready for human trials during which human subjects aregiven the drug.

o There are three phases of human trial.

PHASE I: INITIAL PHARMACOLOGICAL EVALUATION

the drug is given to a small number of healthy volunteers to determine safe dosage levels.

The purpose is to document the dose level at which signs of toxicity first appear in humans, determine a safe tolerated dose, anddetermine the pharmacokinetics of the drug.

Volunteers who give consent to participate are monitored closely during this phase.

Permission must be obtained from the FDA to conduct Phase I clinical trials.

PHASE II: LIMITED CONTROLLED EVALUATION

The purpose of Phase II evaluation is to monitor drug effectiveness and any side effects.

Individuals with the targeted disease participate in this phase of drug trials. example, antihypertensive (blood pressure lowering) drugs will be administered to patients who have hypertension (high blood

pressure) to determine the drugs effectiveness or optimal dose response range and for side effects.

The number of participants is larger than Phase I trials but usually does not exceed 100 persons and every effort is made to use onlypeople who have no other disorders or diseases.

PHASE III: EXTENDED CLINICAL EVALUATION

include many physicians and large groups of participants.

When enough information has been collected to justify continued use of the drug, a New Drug Application (NDA) is submitted to theFDA.

Usually, more than 4 years has passed between the drugs selection and the filing of the NDA.

Phase IV studies are also called post-marketing follow-up.

They are voluntarily conducted by pharmaceutical companies.

These studies continue after the FDA has approved the drug and often include populations such as pregnant women, children, andthe elderly.

Manufacturers can find low-level side effects or can find that a drug is toxic and must be removed from market.

The FDA continues to monitor new drugs even after they are marketed.

Drugs also undergo tests to determine the possible effects on a fetus.

As a result of these tests, drugs are classified using the following Pregnancy Categories.

Category A

Adequate and wel l-controlled studies indicate no risk to the fetus in the first trimester of pregnancy or later.Category B

Animal reproduction studies indicate no risk to the fetus, however there are no well-controlled studies in pregnant women.Category C

Animal reproduction studies have reported adverse effects on the fetus, however there are no well-controlled studies in humans butpotential benefits may indicate use of the drug in pregnant women despite potential risks.

Category D

Positive human fetal risk has been reported from investigational or marketing experience, or human studies.

Considering potential benefit versus risk may, in selected cases, warrant the use of these drugs in pregnant women.Category X

Fetal abnormalities reported and positive evidence of fetal risk in humans is available from animal and/or human studies.

The risks involved clearly outweigh the potential benefits.

These drugs should not be used in pregnant women.

Locating Drug Information

Before administering a drug to a patient, healthcare providers need to know the following information about the drug:

Generic and trade name: The generic name is the official name of the drug while the trade name is the drugs brand name.

Clinical uses and indications for use: Describes the purpose of the drug and when the drug is to be given to a patient.

Mechanism of action: Describes how the drug works.

Adverse and side effects and toxicity: Identifies the effects the drug has other than the therapeutic effect.

Signs and symptoms to monitor: Identifies the patients physiological response that must be evaluated after the drug is admin istered.

What to teach the patient: Specifies instructions that must be given to the patient before and after the drug is administered.


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This information is available in product inserts, various drug handbooks for nurses, and in computerized pharmacology databases and inthe following:

American Hospital Formulary Service (AHFS) Drug Information: Published by the American Society of Hospital Pharmacists, Inc. andcontains an overview of every drug.

United States Pharmacopeia Dispensing Information: Published by the U.S. Pharmacopeial Convention and highlights clinicalinformation, which is the same as the drug inserts found in packages of drugs.

Physicians Desk Reference (PDR): Published by Medical Economics with the financial support of the pharmaceutical industry andcontains the same information as found in the drug inserts.

Physicians GenRx published by Mosby and includes comprehensive drug information product identification charts and product ratingsby the Food and Drug Administration. It also contains cost comparisons between drugs.

Handbook of Nonprescription Drugs: Published by the American Pharmaceutical Association and contains comprehensive informationon over-the-counter drugs including the primary minor illnesses the drug is used to treat.

Medline Plus (http://www.nlm.nih.gov/medlineplus/druginformation.html):An online database produced by the U. S. National Library ofMedicine and the National Institutes of Health and contains information about prescription and over-the-counter drugs and devices aswell as warnings and drug recall information.

Drug Orders

A drug order, also cal led a medical prescription, is an instruction from a provider to give a patient medication.

Providers such as a physician, dentist, podiatrist, advanced practice nurse (in most states), and other authorized licensed healthcareproviders can write a drug order.

Physician assistants can also write a drug order but require the co-signature of a physician.

All drug orders are written on a prescription pad or on an order sheet if written in a healthcare institut ion.

Sometimes orders are written into a computerized drug order system.

A verbal drug order is sometimes given but must be followed up with a written drug order within 24 hours.

Drug orders are written using the abbreviations shown in Table 1-1 and must contain:o Date and time the order (prescription) was issued.o Name of drug and whether or not a generic form of the drug can be substituted for a brand-name drug.o Drug dose.o Route of administration.o Frequency and duration of administration.o Special instructions such as withholding or adjusting dosage based on nursing assessment, laboratory results, or drug

effectiveness.o Signature of the prescriber.o

Signature of the healthcare providers who took the order and transcribed it.
http://www.nlm.nih.gov/medlineplus/druginformation.htmlhttp://www.nlm.nih.gov/medlineplus/druginformation.htmlhttp://www.nlm.nih.gov/medlineplus/druginformation.htmlhttp://www.nlm.nih.gov/medlineplus/druginformation.html


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TYPES OF DRUG ORDERSThere are four types of drug orders. These are:Routine orders: This is an ongoing order given for a specific number of doses or number of days.

Example: 1/31/05 7:30 P.M. Lasix (furosemide) 40 mg., PO, qd (signature)

This is an order to give 40 milligrams of Lasix by mouth once a day. Once a ay medications are generally given around 9 A.M. or10 A.M. based on the healthcare institution or patient choice if at home. Lasix is a diuretic.

One-time order: This is a single dose given at a particular time.

Example: Demerol 50 mg with Vistaril 25 mg IM at 10 A.M. or 2 h before call to the OR.

This is an order to give Demerol (meperidine) 50 milligrams with Vistaril (hydroxyzine) 25 milligrams intramuscularly at 10 A.M. orone hour before call to the operating room.


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PRN: This is an order to give a medication if specific criteria exist, such as a headache, fever, or pain and at the patients request.

Example: Advil 600 mg po q 6 h prm for mild to moderate knee pain.

This is an order to give Advil (ibuprofen) 600 milligrams by mouth every six hours as needed for mild to moderate knee pain.STAT: This is a single dose order to give at once or immediately

Example: Give Benadryl 50 mg. po Stat.

This is an order to give Benadryl (dyphenhydramine) 50 milligrams by mouth immediately.

There are also protocols for administering medications.

This is a set of criteria that indicates under what conditions a drug may be given.There are two types of protocols: standing orders or flow diagrams (algorithms).Standing ordersare an officially accepted sets of orders to be applied by nurses, physician assistants, and paramedics in the care ofpatients with certain conditions or under certain circumstances.

For example, if a patient is not breathing and has no heartbeat, an algorithmhas been developed to administer differentmedications such as epinephrine and other cardiac stimulants to resuscitate the individual.

Other standing orders include orders for Tylenol (acetaminophen) 600 milligrams q 4 h by mouth or per rectum for a temperature> 101.4F.

The Five Rights of Drug Administration

RIGHT PATIENT

means that the healthcare provider gives the drug to the right patient.

Each time a drug is administered, the healthcare provider m ust verify who the patient is by the patients identification bracelet.

This is the preferred method as opposed to identifying a patient by asking his or her name.

Some patients will answer yes to any name and two patients can have similar-sounding names or the same name. Some patientsare not mentally alert and do not remember their name.

Again, check the patients identification every time medication is administered.

RIGHT DRUG

Healthcare providers must be sure that the drug is the correct medication for the patient.

This too leads to errors.

Healthcare providers ask: Was this the drug prescribed on the medication order?

Is the medication order legible and complete?

Why is the patient receiving this medication?

Is the medication consistent with the patients condition? Does the patient have any food or drug allergies?

Providers check the expiration date and return the medication to the pharmacy if it has expired.

If the medication is used past the expiration date, the effect on the patient can be unpredictable.

Healthcare providers check the medication label three times before administering the drug.

First, when they take the medication from the shelf or drawer.

Next, the label should be checked before pouring the drug, and third it is checked after pouring the drug before throwing away thedrug packaging.

RIGHT DOSE

The dose on the medication order must be within recommended guidelines.

The healthcare provider should have a general idea of the dose before performing any drug calculations.

If the calculated dose varies too much from this estimated dose, check with a pharmacist or another appropriate healthcare provider.

Some drug calculations should always be checked by two individuals if the calculation is complicated or the drug has the potential to

be harmful if the dose is too large or too small. Medications that are wrapped and labeled or pre-filled for the exact dose are preferred and can reduce errors.

Healthcare providers should also make sure they use the proper system of measurement when calculating a doseRIGHT TIME

Is it the correct time to administer the drug?

The time is specified in the drug order and may be given a half hour before or after the stated time depending on the policy of thehospital or healthcare facility.

How often a drug is given is dependent on the half-lifeof the drug.

A drugs half-lifeis the amount of time for 12 of the drug to be eliminated from the body. A drug with a short half-lifemust beadministered more frequently than a drug with a long half-life in order to maintain a therapeutic level of the drug in plasma.

The use of military time can avoid A.M. and P.M. errors.

Check if the patient is scheduled for diagnostic or other procedures that might interfere with administration of medications.

Check if the patient should receive the medication even if they are scheduled to be NPO (nothing by mouth).

Healthcare providers should also make sure that medication is given in coordination with meals. Some drugs must be given with meals while other drugs are given a specific period before or after a meal.

Where possible, the medication schedule is adjusted to conform to the patients lifestyle, which may differ from the normal s chedule.

For example, Digoxin might be scheduled for 10 A.M. to conform to hospital policy, but the patient can take Digoxin any time in themorning.

This becomes important once the patient is discharged and takes medication at home.RIGHT ROUTE

The healthcare provider determines the proper routine to administer the drug so the patients body properly absorbs it.

Here are the common routes:o Oral (by mouth): liquid, elixir, suspension, pill, tablet, and capsule


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o Sublingual (under tongue): pill, tablet, and capsuleo Buccal (between gum and cheek): pill, tablet, and capsuleo Topical (applied to skin): cream, ointment, and patcho Inhalation (aerosol sprays): liquido Instillation (nose, eye, ear): liquid, cream, and ointmento Insertion (rectal, vaginal): suppositoryo Intradermal (beneath skin): injectiono Subcutaneous (beneath skin): injection

o

Intramuscular (in muscle): injectiono Intravenous (in vein): injectiono Nasogastric and gastronomy tubes: liquido Transdermal: patches

Make sure that the patient can swallow if the route of the medication is by mouth and stay with the patient until the medication isswallowed.

Enteric coated or time-release drugs should not crushed or mixed.

Caution should be used when administering intravenous medicationsbecause the body quickly absorbs these drugs.o Therefore, healthcare providers need to know expected side effects, effects that occur when the drug is first given, effects

the drug has during its therapeutic peak, and duration of the drugs action.o Caution should be used when administering any medication via this route.

Self-administration of medication (SAM)is the normal practice for patients in the home and workplace.o This method is also used in some acute and longterm care institutional settings.

o

In these settings the nurse gives the patient a packet of medications with instructions that are kept at the bedside.o The patient takes the medication according to the instructions and advises the nurse when he or she has done so.o This practice help patients learn how to manage the medications and prepares them for discharge and use of these

medications in the home.o This method is often used with oncology (cancer) patients and maternity patients.

Patient controlled analgesia (PCA)is a common method of administering intravenous pain medication for many patients.RIGHT ASSESSMENTRIGHT DOCUMENTATIONRIGHT TO EDUCATION

The patient has the right to be told about the medication that is about to be administered.

The patient is told:o The name of the medicationo Why the medication is giveno

What the medication looks likeo How much of the medication to takeo When to take the medicationo When not to take the medicationo What are the side effects, adverse effects, and toxic effects

This information is discussed in the best way the patient can understand.

Healthcare providers should avoid speaking in medical terminology and, instead, use common words and expressions that arefamiliar to the patientand always in the language that the patient speaks.

The patient provides feedback that he or she understands everything about the medication.

It is common for the healthcare provider to ask the patient to tell in his or her own words what was told to them about the medication.

The patient is also shown how to keep track of multiple medications.

Typically, the patient is encouraged to keep a list of medications.

The list should have the name of the medication, dose, time the medication is to be taken and the name and phone number of the

prescriber who ordered the medication.RIGHT EVALUATIONRIGHT TO REFUSE MEDICATION

A mentally competent patient has the right to refuse medication.

Refusal is documented on the patient record.

Patients should be advised of the consequences of the refusal to take the medication such as a worsening of the condition.

As a general rule, every effort is made to encourage the patient to take the medication.

However, no one should physically force a patient to take medication.

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LESSON 2. Basics of Pharmacology