Module 5 - Non-prescription drugs Flashcards
2 categories of drugs
- prescription drugs
- non prescription drugs
OTC drugs
Over the counter drugs
sold without a prescription based on the premise that the general public is able to diagnose mild symptoms and to select appropriate agents to treat these symptoms
Guidelines for using an OTC drugs
- OTC drugs are not a replacement for prescription drugs or care by a healthcare professional, and should only be used in certain circumstances
- illness and or symptoms:
- the illness of symptoms are mild
- serious illness or symptoms should be treated by a physician
- if the illness or symptoms become worse, consult a physician
Adverse effects of OTC
- if adverse effects occur, stop taking the drug
- the use of OTC products can have serious consequences
- OTC products can cause toxicities on their own as well as cause drug interactions with other drugs, including herbal and prescription drugs
Safety and efficacy of OTC drugs
sale of OTC drugs is controlled by a section of the food and drugs act
all OTC products are subjected to rigorous preclinical testing for safety
post-market safety surveillance is also conducted on all OTC products
not all OTC products have been subjected to randomized controlled trials
- instead, they are available because they have been on the market and have been used for decades
- this is known as grand-parenting: a process where new regulations do not apply to those products already on the market
concerns with the lack of randomized control trials:
- some of the older OTC drugs may not be effective
- the only appropriate manner for assessing the efficacy of any drug is a randomized control trial
- for some older OTC drugs may have serious toxicities
Selection of appropriate OTC drugs
- proven efficacy and known toxicity
- simple formulation and ingredients
- brand vs generic
- appropriate and effective dose
Common OTC drugs
- internal analgesics
- antihistamines
- drugs for excess stomach acid
- decongestants
- cough suppressants
- sleeping aids
- laxatives
- antidiarrheals
- hydrocortisone cream
- suncream
Internal analgesics
provide pain relief
3 common OTC analgesics:
1. acetylasalicylic (aspirin)
2. Acetaminsophen (tylenol)
3. NSAIDS (advil and aleve)
acetylasalicylic (aspirin)
relieves pain, fever, inflammation by inhibiting the synthesis or prostaglandins
in low doses, it prevents stroke and heart attack by inhibiting clot formation
Adverse effects:
1. gastric irritation
2. tinnitus
3. Reyes syndrome
4. allergic reaction
Acetaminophen (Tylenol)
Mechanism of action: inhibition of prostaglandin synthetase which is the enzymes responsible for the formation of prostaglandins
Therapeutic use: effective analgesic and antipyretic but not an effective anti-inflammatory
Adverse effects:
- overdose can lead to fatal liver injury
- individuals with alcohol use disorder and liver disease are more susceptible to the liver toxicity
NSAIDs (advil and aleve)
internal analgesics are non-steroidal and anti-inflammatory drugs
Therapeutic use: effective analgesics, antipyretic, and anti-inflammatory compounds
Adverse effects:
- gastric irritation
- skin rash
- dizziness
- blurred vision
- fluid retention
Mechanism of action of internal analgesics
- when tissue damage occurs, arachidonic acid is released
- arachidonic acid can be converted by the enzyme COX-1 into prostaglandins which are involved in many beneficial effects such as gastroprotection, platelet aggregation, renal protection, vasodilation, and bronchodilation
- arachidonic acid can also be by the enzyme converted into COX-2 into inflammatory prostaglandins causing detrimental effects such as inflammation, pain, fever, and decreased platelet aggregation
- analgesics work by blocking one or both of the enzymes, decreasing the production of prostaglandins involved in inflammation, pain, fever, but also decreasing the production of the protective prostaglandins
Internal vs topical analgesics
most pain is best treated with an internal analgesic, but some topical products are available for the relief of pain associated with minor sprains and joint pain
Antihistamines
- used in the treatment of all allergy symptoms such as hay fever
- these drugs act by blocking histamine receptors, thereby inhibiting the binding of histamine to its receptor, decreasing allergy symptoms
First and second generation antihistamines
- antihistamines are classified into first and second-generation agents due to slight differences in their pharmacology
- the first generation causes sedation and drowsiness
- diphenhydramine
- the second generation is less sedating and is the preferred agents
- cetirizine
- the first generation causes sedation and drowsiness
Drugs for excess stomach acid
designed to either neutralize stomach acid or decrease stomach acid secretion
three main classes of drugs for excess stomach acid:
1. antacids
2. h2 inhibitors
3. Proton pump inhibitors (PPIs)
Antacids
- neutralize the acid in the stomach
- objective is to hold the pH of gastric contents at about 4 by an acid-based chemical reaction
- systemic:
- given orally and are absorbed by the GI tract
- example: tums (calcium carbonate)
- non-systemic:
- also given orally but not absorbed and thus do not cause systemic alkalosis
h2 inhibitors
- target acid secretion in the stomach
- transfer of protons (H+) into the stomach in exchange for potassium (K+), histamine is involved in the release of stomach acid
- without H2 receptor antagonist
- when the histamine receptors in the acid-secreting cells of the stomach are activated, the proton pump is turned on and acid secretion is increased
- with H2 receptors
- these drugs are free from major adverse effects, although skin rashes, headache, and confusion are infrequently reported
PPIs
- target acid secretion in the stomach
- example: omeprazole
- permanently bind to the proton pump, inhibiting acid secretion by 90% or more
- they are the most effective drugs available for suppressing acid secretion
- the frequency of adverse effects is low and includes diarrhea, headache, and abdominal pain
- these drugs were only available by prescription until recently
Decongestants
- congestion is caused by the dilation of small blood vessels, which allows fluid to leak from the vessels into the spaces between cells
- decongestants cause constriction of blood vessels, preventing the accumulation of fluid and thereby reducing congestion
Long term use of decongestants
leads to local irritation and chronic rhinitis (long-lasting congestion)
Cough suppressants
centrally acting cough suppressants:
- block the processing of information in the brain, reducing the frequency of the cough
- codeine is present in some OTC cough suppressants since they suppress the cough centre
- an alternative OTC cough suppressant is dextromethorphan hydrobromide
peripheral cough suppressants:
- block the nerve endings in the throat and bronchioles, inhibiting the stimulus to cough
- in these agents, camphor and menthol are added to vaporizers or rubbed on the throat and chest
- the efficacy of these products is questionable
Sleep aids
Intended to help an individual fall asleep or to relieve sleeplessness
- example: melatonin
many nighttime preparations of OTC drugs also exist (Nyquill, Aleve PM)