Pharmacology CHAPTER 3 Sources & Bodily Effects of Drugs.

Pharmacology

CHAPTER 3

Sources & Bodily Effects of Drugs

A Drug

• Any chemical substance taken into the body for the purpose of affecting body function

Source of drugs

• Way back when….plants were the primary source of drugs used on the human body. Plants such as:

• Berries• Bark• Leaves• Resin from trees• Roots• These all aid the body and are still used today• Aloe vera

Minerals

• These found their way into drugs also:

• Iron

• K+

• Sulfur

• silver

Animals & Humans

• Substances lacking in the human body can be replaced with similar substances from animals, glands, organs and tissues

• Human cadavers can be used to extract GH

Synthetic Drugs

• Competitive research and big industries are experimenting with chemicals to discover cures for diseases

• HIV research is prevalent now

• Dual chemicals on combination are being created like Caduet…it combines Lipitor and Norvasc

Effects of Drugs

• When introduced into the body, all drugs cause cellular changes known as drug actions

• There is then some physiological change

• Drugs are categorized by:

• Systemic effect

• or

• Local effect

Systemic Effect

• This reaches widespread areas of the body like acetaminophen suppository

• When you give Tylenol PR, it has the ability to absorb and get distributed throughout the body to cause a general reduction in fever

Local Effect

• This is limited to the area of the body where the medicine is administered such as:

• Dibucaine or Nupercainal, this med is applied rectally and only affects the rectal mucousa to reduce hemorrhoidal pain

What is the process that makes a med work when taken orally

• Within the body, drugs undergo several biological changes and there are 4 drug processes that occur:

• 1. Absorption – getting into the bloodstream• 2. Distribution – moving from the bloodstream

into tissues and fluids of the body• 3. Metabolism – physical and chemical

alterations that a substance undergoes in the body

• 4. Excretion – eliminating waste products of drug metabolism from the body

Interruption

• There cannot be any interruptions in any of the 4 processes or the drug will not be properly processed by the body

Absorption

• Takes place in areas such as:• Mucosa of stomach, mouth, small intestine or

rectum• Blood vessels in the muscles or sub Q tissues• Dermal layers

• If administration of any med is done incorrectly, the drug may be destroyed before it reaches the bloodstream such as giving antibiotics on a full stomach vs. on an empty stomach

Absorption of Tetracycline

• Ph plays a big part in absorption

• Drugs of alkaline nature do not absorb well through the stomach

• Tetracycline is recommended to be given on an empty stomach so that the ph is not altered

• If tetracycline is given with milk or antacids, it will not be absorbed properly

Infants and medications

• Syrups and solutions may not be absorbed well if infants drink formula first

Lipid Solubility

• Substances high in lipid solubility are quickly and easily absorbed in the mucosa of the stomach

Presence or absence of food in the stomach

• Food in the stomach tends to slow absorption d/t a slower emptying of the stomach

DISTRIBUTION

• The primary site of process is through capillaries and across cell membranes

• Poor circulation/impaired flow of blood may prevent the drug from reaching tissues

• Some drugs have targeted tissues that it goes to and works well in, some drugs can cross placenta barrier causing problems for baby

Metabolism

• When the drug reaches the liver, it is broken down and altered to more water-soluble by-products, thus the new drug may be easier excreted by the kidneys

• If a pt has a broken liver, how will the break down the med? The med accumulates and becomes toxic

Excretion

• Most medications are eliminated from the kidneys

• Some meds are eliminated through the lungs like exhaled gases from anesthesia

• If a drug is not excreted properly, a cumulative effect may occur and cause toxicity.

• We don’t need a cumulative effect of meds, they are designed to be given in just the amount to make them work

Digoxin

• has this cumulative effect and drug levels must be obtained

• Dig is used to slow the HR, if it accumulates, what will happen?

• Bradycardia

What other things affect the speed and efficiency of a drug?

• AGE – metabolism and excretion are slower as we age leading to possible cumulative effects. Children react more rapidly and in unexpected ways

• WEIGHT – generally, the bigger the pt, the more medicine that person would receive. There is an individual variation in the sensitivity of meds. Some meds are weight based, especially in children

• SEX - women respond differently to meds than men do. The ratio of fat per body mass differs and hormone levels differ. Pregnant women must not take drugs or limit what they take.

•

Physiological State

• When a person feels good, they are more productive, when they feel good while on their medicine, they are more likely to continue to take it

Placebo Effect

• The more positive the pt feels about the med he is taking, the more positive the physical response

• PLACEBO – an inactive substance that resembles a medication, although there is no drug present

• Example : birth control has 3 weeks of hormone pills and 1 week of placebo, it’s usually to remind the taker, to keep taking this important pill

Drug Interactions

• Be careful when combining meds, one can affect the other and even make it not work well or cancel out its effects

Terms used to describe drug interactions:

• Synergism – the action of 2 drugs working together simultaneously for an effect that neither could produce alone. These drugs together are said to be synergistic. Phenergan and demerol given together are used to relieve pain, both can be given in smaller amts than if given alone

Potentiation

• Potentiation – the action of 2 drugs in which one prolongs or multiplies the effects of another. Ultram is used in replacement of a narcotic like morphine. If taken together, Ultram potentiates the effects of the morphine and now it’s like you took 3xs the amount of morphine…can cause trouble

• Or like Tetracycline potentiates warfarin

Antagonism

• Antagonism – when one med cancels out the effect of the other med.

• Such as narcan to reverse the effects of demerol or morphine if pt had respiratory depression

• Drs. Must be knowledgeable about all of these terms because if they order meds that react with each other, pts will run into trouble

Dosage

• Is defined as the amount of drug given for a particular therapeutic or desired effect

Minimum dose

• Smallest amount of a drug that will produce a therapeutic affect

• Example: Tylenol lists dosages on the back of the bottle

• (Range of Tylenol is 10-15mg/kg)

• Bottle recommends the minimum dose

Maximum Dose

• Largest amount of a drug that will produce a desired effect without producing symptoms of toxicity

• Range of Tylenol 10-15mg/kg 15mg/kg is the maximum dose allowed

Loading Dose

• Initial high dose (often a maximum dose) used to quickly elevate the level of the drug in the blood (often followed by a series of lower maintenance doses)

• Drs. Order this with the 1st doses of pain medicine, they want to get the pain under control quickly

• When you are ordered an antibiotic for strep, Dr. tells you to take 2 tabs tonight, to load up on the med

Routes to administer meds

• GI Tract :

• Oral – P.O.

• Nasogastric tube - NGT

• Rectal - PR

• Parenteral Routes (these include anything other than the the GI tract):

• Sublingual or buccal- SL

• Injection routes – • Intravenous – (IV)• Intramuscular – (IM)• Subcutaneous – (Sub Q)• Intradermal – (ID)

• Topical – (T)

• Dermal – (D)

• Mucosal -

• Inhalation – breathing it in

The good with the bad…

• There are advantages and disadvantages of taking meds in any of the listed routes:

• P.O. meds take longer to work than IV

• We would like to try and give all meds by mouth if possible…this is the normal way

• IV route is the fastest

PATENT

• Wide open, to keep clear and free

• Used often with IVs or feeding tubes

• Example:• You must flush a gastrostomy tube with tap

water upon the completion of a feed to maintain the patency of the tubing

IV Route

• Meds must be given in smaller amts through IV• Can be dangerous if not deadly if given too

much IV• NEVER GIVE ANY SUBSTANCE IV THAT IS

NOT A PATENT SOLUTION. • YOU SHOULD BE ABLE TO SEE THROUGH IT

SOMEWHAT. NEVER PINK, OPAQUE YELLOW OR WHITE OR ANYTHING STICKY…NOT USUALLY FOR IV USE

Parental routes

• This way of giving meds is usually for the sickest pts who cannot take P.O.

• If you have a med that is not suitable for the GI tract or absorption, then it’s given another way like vitamin B12, just given in IM form

Unexpected Responses To Drugs

• These are adverse drug effects

• These are what happens to pts who are allergic OR this is what can happen from taking a particular med

Teratogenic effect

• The development of abnormal structures in an embryo resulting in a severely deformed fetus

• Effects from drug administration by the pregnant mom. Fetus can suffer physical defects or death

Idiosyncrasy - A structural or behavioral characteristic

peculiar to an individual or group • Unique, unusual response to a med that makes one

person react differently than another, hmmm… peculiar isn’t it?

• When doses of a drug that would have a known and predictable effect cause a toxic or opposite effect, an unusual effect or no effect, hmm… peculiar isn’t it?

• It can manifest as an accelerated response to the usual therapeutic dose of the drug hmm… peculiar isn’t it?

Paradoxical – seemingly contradictory but demonstrably true

• Opposite effect from that which is expected

• Such as that benadryl acting opposite of how it’s really supposed to act

• Benzodiazepines have been known to cause severe behavioral changes such as mania, schizophrenia, anger, impulsivity, and hypomania

Tolerance

• Decreased response to a drug that develops after repeated doses are given. Now to achieve the desired effect of the med, the person must increase the normal dose just to get some type of effect. If this doesn’t work, the drug is stopped and another drug is used

• Tell story of Jenny and Benadryl and people who take narcotics

Dependence

• Acquired need for the drug that may produce psychological or physical symptoms of withdrawal when the drug is discontinued

• Tell Andy story about increase need for narcotics and withdrawal symptoms

Psychological Dependence

• Involves only a psychological craving, no physical symptoms of withdrawal are present other than anxiety

• Smoking cessation causes both psychological and physical dependence

• Smoke with drinking and every time you drink, you need to smoke, even after you have stopped, it’s habit

Physical Dependence

• Exists when cells actually have the need for the drug

• SYMPTOMS OF WITHDRAWAL:• Retching• Nausea• Pain• Tremors• Sweating• Can cause death if in withdrawl too long

Hypersensitivity

• When a person has an immune response (allergy) to a drug. Can be of varying degrees:

• Mild with no immediate effects. Rash or hives may appear after 3 or 4 days of drug therapy

• May develop after uneventful previous uses…body is building antibodies to it and one day POW!!!! Immune response

• More likely to exist in pts with other known allergies

• NAUSEA, VOMITING, DIARRHEA• ARE NOT CONSIDERED SIGNS OF

ALLERGIES• These are considered to be more like side

effects. Just because someone has these does not mean they should never have these again.

• Benadryl can fix some of the side effects that cause discomfort to pts

Maintenance Dose

• Dose required to keep the drug blood level at a steady state in order to maintain the desired effect

• Drs. Will order a PCA pump to keep the same level of pain medicine going continuously, they want to maintain this dose to control pain better

Toxic Dose

• The amount of drug that will produce harmful side effects or symptoms of poisoning

Lethal Dose

• Dose that causes death

Therapeutic Dose

• Dose that is customarily given. Average adult dose is based on a body weight of 150lbs. It is adjusted according to variations from the norm

Anaphylactic Reaction

• Severe, possibly fatal, allergic response• Signs:• Itching• Urticaria (hives)• Hyperemia (reddened, warm skin)• Vascular collapse• Shock• Cyanosis• Laryngeal edema• dyspnea •

Treatment of anaphylaxis

• CPR

• Drugs – epinephrine (adrenaline) to get the heart going and raise BP

• Corticosteroid – (solu-medrol) to reduce inflammation

• Antihistamine – (benadryl) to suppress histamine to reduce redness, itching, edema

Anaphylaxis is seen in…

• 1. Certain antibiotics, especially penicillin

• 2. X-ray dyes containing iodides, if a pt has an allergy to shell fish, NO DYE

• 3. Insect stings

Information

• It’s important to get a history on your patient• You can prevent a reaction or side effects if you

are aware of what they can and cannot have• Pts who have allergies should wear med-alert

bracelets or necklaces or carry a card in their wallet

• If a pt has a sensitivity or allergy to one med, they may have other allergies that haven’t been figured out yet

THE END