Lesson A4 - DRUG TOXICITY AND ROUTES OF DRUG ADMINISTRATION Flashcards
With the widespread distribution of drugs, we have the twin hazards of ____________ and __________
Accidental poisoning, Suicide
When do the majority of accidental poisonings happen? What are the main drug in these poisonings?
- Children under five years of age
- Acetaminophen or asprin
True or false? Iron is is dangerous if taken in large doses
True
What is the major drug group that has been implicated in suicide attempts
Barbiturate group and similar drugs
Barbiturate tablets were once dispensed as __________ or _____________
Sedatives, Sleeping pills
Why must people who are severely depressed not take a large amount of barbiturate or similar drugs?
Because they may use these drugs to commit suicide
What is the other name for valium?
Diazepam
What group of drugs in the western world has been used over the barbiturate group because of the enhanced safety. List one of the drugs in this group? What were they used for?
- Benzodiazepine group
- Diazepam (Valium)
- Sedation and sleeping pills
What group of drugs has been widely accepted for the use of sedation and sleeping pills?
- Benzodiazepine group
What happens when Benzdiazepine is taken for it’s sedative effects and it is overdosed?
- Over-sedation
- An extension of the normal therapeutic effects
What are anticoagulants used for?
To prevent blood clots
What will an overdose of anticoagulant drugs cause
- Bleeding
- An extension of the normal therapeutic effects
What side effect do digitalis drugs used to strengthen the heart muscle (Used in patients with congestive heart failure)
- produce nausea, vomiting, and abnormal colour vision
- Unrelated to their main action
What is the drug succinylcholine used for?
Muscle relaxant
How is the muscle relaxant drug succinylcholine inactivated in the body? What are some problems that can arise?
- By an enzyme present in the blood
- Some patients 1 in 3000 may not have this enzyme and therfore cannot digest it
- Because they can’t digest the drug it acts for a very long time
What are the 4 adverse effects of drugs?
- Extension of therapeutic effect
- Unrelated to main drug action
- Idiosyncrasy
- Drug Allergy
When a new drug is introduced they proceed through 3 stages, What are these 3 stages
- Panacea
- Poison
- Pedestrian
What is the Panacea stage of the introduction of a new drug?
When the drug is first marketed with considerable advertising, it is thought that the
drug is a major new advance.
What is the Poison stage of the introduction of a new drug?
After the drug has been in use for a few months, additional adverse effects usually
become apparent and sales of the drug drop precipitously. The drug is then thought to be a poison.
What is the Pedestrian phase of the introduction of a new drug?
With the further passage of time, the benefit/risk ratio of the drug is easier to
assess and it is realized that the drug is neither a panacea nor a poison, but rather an average (or pedestrian) drug.
What are the 4 reasons that a drug may be thought as little or no toxicity when first introduced and then later turns out to be significantly toxic?
- The toxic reaction may be a rare event
- The toxic reaction may only appear after the drug has been in prolonged use
- Toxic effects not detectable in animals
- Toxic effect may be unique to a particular period
The antibiotic, chloramphenicol, was used for several years before it was realized that _______________ patients, it could cause death of the _______________________ leading to death of the patient.
1 in 50,000, cells in the bone marrow
What was the drug streptomycin used for and what could it cause if used for a prolonged period?
- Used for the treatment of tuberculosis
- It can cause deafness
What are some side effects that are not detectable in animal testing
Headache, insomnia, nausea and mental
disturbances will not be readily picked up in animal testing.
What did Thalidomide cause to the fetus in pregnant women
- Abnormal limb growth (phocomelia)
What dose a higher vs lower therapeutic index mean?
- The higher the therapeutic index the greater the safety of the drug and wider the safety margin
- The lower the therapeutic index –> required caution in use
What is the median toxic dose mean?
This is the dose that is toxic to 50% of the population of animals
True or false? The so-called ‘usual dose’ of some of our most effective drugs will accomplish little in some persons, cause serious toxicity in others, and be fully satisfactory in some.
True
What happens when a patient takes a drug
It must first be absorbed into the blood stream, then carried by the blood to its site of action where it will exert its effect.
- True or false. When the same dose of a drug is given to different individuals, the concentration of the drug in the blood can vary by a factor of as much as 10 between different people.
- And why??
- True
- The reason is that there are wide differences in the rate at which a drug is absorbed and eliminated in different patients.
What are the 4 reasons that the same dose of a drug on various people can have different concentrations in their blood?
- Genetic Factors
- Environmental factors
- Disease
- Presence of other drugs
What is the drug phenytoin (Dilantin) used for?
For the prevention of epileptic attacks
What is lithium used to treat? What is important about it?
- Used for manic-depressive illness
- Concentration in blood levels must be monitored because they need to be within specific limits
What are the 2 ways that a drug can enter the body?
Enteral or parenteral route
What does it mean when we say a drug enters through the enteral route?
It means that the drug is placed directly into the gastrointestinal tract
What does it mean when we say a drug enters through the parenteral route?
It means it is given by a route such that gastrointestinal tract is bypassed
What are the 3 enteral routes that drugs can be administered?
- Drug taken by mouth
- Rectal administration
- Under the tongue
What are the commonest forms of parenteral administration of drugs
- Intramuscular
- Subcutaneous
- Intravenous
What are less common methods of parenteral administration of drugs?
- Inhalation
- Into the spinal canal
- Chemicals may penetrate the skin and get into the circulation
What are the 6 ways of parental administration of drugs?
- Intramuscular
- Subcutaneous
- Intravenous
- Inhalation
- Into the spinal canal
- Chemicals may penetrate the skin and get into the circulation
What is neuritis
Inflammation of the nerve
Why was the hypodermic syringe invented in 1853?
To inject morphine subcutaneously to relieve pain of neuritis ( inflammation of the nerve)
What are some advantages of intravenous administration?
- The drug is placed directly into the circulation with a minimum of delay
- The rate of drug infusion can be held constant for long periods using a constant infusion apparatus.
- Some drugs such as nitrogen mustard, which are used in certain types of cancer, are intolerably painful when given by subcutaneous or intramuscular routes.
Name 3 disadvantages to intravenous administration
- A drug injected into a vein cannot be retrieved ( When a drug is given by mouth they can remove it by getting the patient to vomit)
- If the drug is given too rapidly into a vein, it can lead to disaster. ( If a drug is injected over a
period of one second, a very high concentration of the drug reaches the heart.) –> heart rhythm or death - There is an ever present danger of infection if a sterile technique is not used. ( EXAMPLE not using new needles
Injections by intravenous route are usually done ______________
Slowly
After injection of a drug into skeletal muscle, the drugs are generally ___________________ into the blood supply of the muscle and will usually act after a period of _______________ minutes
Rapidly absorbed, 10 to 30 minutes
The absorption of drugs into the blood following a _____________ injection is slightly _________ than that following ____________ injection
Subcutaneous, slower, intramuscular
Why is the absorption of drugs via subcutaneous injections slightly slower than that following intramuscular injection?
Blood flow is somewhat poorer in the subcutaneous tissues than in skeletal muscle
Why sometimes are drugs deliberately injected into skeletal muscle in a form in which they can only slowly dissolve and pass into the blood stream?
Sometime is it desirable to have a drug act over a period of many hours
True or False? Poisoning can happen through skin?
True
What are some of the chemicals that people can get poisoned through the skin?
- Insecticides (Parathion and malathion)
- Nicotine (frequently used in insecticides)
Why are Parathion and malathion harmful to the body?
Parathion and malathion are inhibitors of the enzyme, acetylcholinesterase, and this leads to the build-up at nerve terminals of the neurotransmitter, acetylcholine.
What is an antidote of parathion and malathion poisoning?
Antidotes are atropine to block acetylcholine receptors, and pralidoxime to regenerate the enzyme, acetylcholinesterase.
Transdermal application systems have been developed over the past 2 decades. Why are all drugs used in the manner effective at small doses?
Because only a small amount of a drug can be transferred across the skin
