19. Pharmacology - Intro Flashcards
Characteristics of allopathic therapies
Treats symptoms Symptom care Suppresses symptoms Toxic Invasive Adverse effects/aggravations can be severe and permanent
Examples of allopathic therapies
Drugs Surgery X-rays Radiation Chemicals
Characteristics of natural therapies
Treats whole person Patient care Corrects vital force of body Non-toxic Non-invasive Aggravations/healing crisis (not life threatening)
Examples of natural therapies
Nutrition Herbs Essences Oils Physical therapies
What is suppression?
Disappearance of an illness without having healed it
What can suppression cause?
The disease to go deeper into the body
It can reappear in another form
Adverse effects
Reoccurrence
Examples of suppressive treatments
NSAIDs Steroids Analgesics Anti-hypertensive medication Chemo Radiation
Classifications of drugs
Anti-microbial Anti-inflammatory Analgesic Anti-convulsant Anti-cancer
Naming conventions for drugs
Proprietary/Brand/Trade name e.g. Anadin, Nurofen
Generic name e.g. paracetamol
Chemical name e.g. N-acetyl-para-aminophenol
What is indication?
Approved uses of disease for which the drug has been proved effective
What is contraindication?
Circumstances under which the drug shouldn’t be taken
Should aspirin be taken by asthmatics?
No
What is ‘adverse effects’?
Additional effect on the body even at the recommended dose e.g. drowsiness
If a patient is experiencing adverse effects from a drug, what should you do?
Refer back to GP
Classifications of adverse effects
Predictable
Unpredictable
What are predictable adverse effects?
Exaggerated physiological effect
Toxicity
What are unpredictable adverse effects?
Allergy
Idiosyncratic reaction
Adverse effects of statins
Reduced CoQ10 levels leading to: Muscle pain Liver dysfunction Renal failure Cataracts
What is CoQ10?
Powerful antioxidant found in mitochondria
More concentrated in cells that are more active
Examples of hypersensitivity adverse effects
Penicillin - nausea, vomiting, pruritus, hives
Local anaesthetics
What is an idiosyncratic reaction?
Reaction to a substance specific to the sufferer
What can cause an idiosyncratic reaction?
Enzymopathy
Disturbance in enzyme function
Example of idiosyncratic reaction
Excessive excitement in children after taking a sedative drug
Categories of drug interactions
Synergism
Antagonism
What is synergism?
Effect of drug increased
Examples of drug synergism
Painkiller combination
Some supplements e.g. fish oils and anti-coagulation medication
What is antagonism?
Effect of drug decreased
Examples of drug antagonism
Vitamin K counteracts anti-coagulants
What is an iatrogenic effect?
Induced by physician/practitioner
Why can some interactions between orthodox medications be fatal?
Some medications block liver/intestine enzyme pathways
Some affect liver detoxification
Facilitates an iatrogenic overdose
Why can grapefruit juice significantly alter drug levels in the body?
Inhibits enzyme CYP 3A4 in intestinal wall
Leads to excessive quantity of the drug
What does enzyme CYP 3A4 do?
Breaks down/metabolises hundreds of medications
Which drugs can be affected by grapefruit juice?
Statins
HRT/OCP
Anti-retrovirals
Calcium channel blockers
How long can the inhibition of CYP3A4 last?
Up to 24 hours
What impact does the lasting effects of grapefruit juice on CYP3A4 have?
Can’t separate grapefruit and drugs
Why can the consumption of alcohol significantly interact with drugs?
Alcohol can inhibit a drug’s metabolism by competing with the drug for the same set of metabolising enzymes
What can long-term alcohol ingestion have on drug interaction?
May activate drug metabolising enzymes, therefore decreasing the drug’s availability
Diminishes the drug’s effects
Can also transform some drugs into toxic chemicals that can damage the liver/other organs
What effects can alcohol have on sedative/narcotic drugs?
Magnify the inhibitory effects of the drugs in the brain
What effects can alcohol have on slow-releasing drugs?
Can force them to release faster - resulting in overdose
Can some herbs interact with drugs?
Yes
Example of St John’s Wort interacting with drugs
St John’s Wort reduces the effectiveness of anti-retroviral drugs for HIV
Examples of liquorice interacting with drugs
Digoxin - can increase adverse effects by lowering potassium levels
Interferes with ACE inhibitors and diuretics
Contraceptives - can elevate blood pressure and lower potassium
May effect breakdown of drugs in the liver
Examples of senna interacting with drugs
Can increase adverse effects of digoxin
Can cause diarrhoea if taken in high doses
Can increase the effect of warfarin
May cause dependence if taken long-term
What is pharmacokinetics?
How drugs are absorbed and moved around the body
What does pharmacokinetics comprise of?
Absorption
Distribution
Metabolism
Excretion
What is pharmacodynamics?
How drugs exert their effects e.g. block receptors
What factors should be considered when administering a drug?
Cost Patient compliance Bioavailability Speed of effects Safety Food interactions Ability to absorb Whether it bypasses the liver
In what ways can drugs be administered?
Orally Sublingually Injection Inhalation Topically
Types of oral drugs
Tablets
Capsules
Liquids
Where are oral drugs absorbed?
Stomach
Intestines
What does the bioavailability of oral drugs depend on?
Release of the active form
Destruction in the gut
Absorption
Loss of active form via the first pass
Types of sublingual drugs
Nitro-glycerine (GTN)
B12
Homeopathy
What is the benefit of sublingual drugs?
Avoids first pass effect in the liver, so avoids becoming deactivated
Categories of drug injections
Intradermal
Subcutaneous
Intramuscular
Intravenous
Examples of drug injections
Insulin into adipose tissue
B12
Examples of inhalation drugs
Bronchodilators
Anaesthetics
Essential oils
What do topical drugs need to be to able to penetrate the skin?
Lipid soluble
Examples of topical drugs
Nicotine patch
Oestradiol HRT patch
Steroid creams for psoriasis/eczema
Where do suppositories/pessaries go?
Rectum
Vagina
What can suppositories/pessaries be used for?
Haemorrhoids
What is an enema?
Procedure using gas or water to extract/clean
Which circulatory systems do drugs enter?
Blood
Lymphatic
Why do lipid-soluble substances cross cell membranes easily?
Due to the phospholipid bilayer
What barriers are in the body to inhibit the movement of drugs?
Placenta
BBB
Why can the BBB make treating pathologies of the nervous system difficult?
Drug can work in the general circulation but can’t cross into the brain
Which substances can cross the BBB?
Very lipophilic substances
Substances actively transported
Why should care with medications be taken during pregnancy?
The placenta is much less effective than the BBB at keeping medications out
What is dosage?
The amount of drug required to produce the desired effect
How is dosage calculated?
To ensure a therapeutic concentration is maintained for the time period required
How is dosage usually expressed?
By a weight/measure and by time e.g. 2x BD, 3x TDS
What are dosage parameters?
Weight
Age
Sex
How eliminated and rate
What is dosage frequency based on?
Absorption
Transport
Half-life
What factors can influence patient compliance?
Feels better
Forgetting
Inconvenience
What can taking a drug too frequently or at a higher dose lead to?
Toxicity
What is the compliance rate for a once a day dosage regime?
95%
What is the compliance rate for a twice a day dosage regime?
76%
What is the compliance rate for a three times a day dosage regime?
75%
What is the compliance rate for a four times a day dosage regime?
58%
What is ‘half-life’?
Time it takes for a drug’s concentration in the body to fall by half
What does half-life reflect?
The rate of elimination
How does a long half-life affect dosage?
Take less often
Types of dosing regimes
Toxic dosing
Sub-optimal dosing
Therapeutic dosing
What is toxic dosing?
Drug given too frequently or at too high a dose
What is sub-optimal dosing?
Drug given too infrequently or at too low a dose
What is therapeutic dosing?
A dosing regime that maintains drug concentration within the therapeutic range
What is a loading dose?
A larger dose given initially, followed by smaller maintenance doses
What is the benefit of a loading dose?
Allows the drug to rapidly reach therapeutic levels
When can a loading dose be done?
When there are no adverse effects from taking a larger dose
What can affect drug absorption?
Large or small molecules Lipid soluble vs water soluble Acid vs alkaline Chemically reactive vs chemically inert/stable Gut health Digestive function Foods ingested
Characteristics of lipid soluble drugs
Get quicker into the cell
Characteristics of water soluble drugs
Repelled so slower getting into the cell
Characteristics of acid and alkaline drugs
Best absorbed in an environment that matches the drug type
e.g. aspirin is acidic and is absorbed in the stomach (which is also acidic)
What happens to the metabolism of synthetic drugs?
Body won’t have a natural mechanism to remove it
It may be metabolised to render it inactive
Which enzyme system becomes active with exposure to certain drugs?
CYP450
Where do CYP450 enzymes exist?
Intestines
Liver
Why are some drug metabolites toxic?
Products formed during metabolism can be hepatotoxic and deplete the liver of its natural antioxidant (glutathione)
Why can’t some drugs be taken orally?
They are metabolised so quickly by the liver
Where does most drug excretion take place?
Kidneys
Intestines
How do the kidneys excrete drugs?
Glomerular filtration
Tubular secretion
How do the intestines excrete drugs?
Bile
What can also assist in drug excretion?
Lungs
Skin
What are the main modes of action for drugs?
Specific
General
Placebo
What is a specific mode of action?
Chemical structure is paramount
What is a general mode of action?
Physical and chemical properties are important
Examples of general modes of action?
General anaesthetics blocking impulses in neurons
Antacids neutralising stomach acid
What does the effectiveness of a placebo depend on?
Patient having belief in the remedy/practitioner, confidence from their consultation and the form of remedy
What are agonist drugs?
Bind to receptors and stimulate increased activity
Example of an agonist drug
Blue inhaler
What are antagonist drugs?
Drugs that bind to receptors and block the natural chemical from attaching and sending its message
Example of an antagonist drug
Betablockers
