M5S1 Over The Counter Drugs Flashcards
Prescription drugs
-restricted to sale by prescription only
Non-prescription dugs
-drugs that can be sold to the general public without a prescription
-includes over-the-counter (OTC) drugs
Over-the-counter drugs
-sold without prescription based on premise the general public is able to diagnose mild symptoms and access appropriate agents to treat the symptoms
Guidelines for using OTC drugs
-not a replacement for prescription drugs or care by a healthcare professional
-should only be used in certain circumstances
Illness and/or symptoms
-ex. Fever for cold
-are mild as severe illness and/or symptoms should be treated by physician
-if illness become worse, consult physician
Adverse effects
-if occur, stop taking immediately
-important to recognize that use of OTC products have serious consequences
-can cause toxicities on their own
-can cause drug interactions with other drugs including herbal and prescription drugs
Consultation
-if unsure, pharmacist can help chose which
-self-mediation with OTC should not exceed 2 weeks without consulting a physician
Safety and efficacy of OTC drugs
-sales controlled by section of Food and Drugs Act
-act controls safety, efficacy, advertising, and sales of these products
-all subjected to rigorous preclinical testing for safety
-post-market safety surveillance also conducted on all OTC products
-number of recent OTC additions available by prescription before being released on OTC market (extensive clinical trials were conducted for initial market approval)
Note: not all OTC products have been subjected to randomized controlled trials. Instead, available because have been on market and have been used for decades (ex. Acetaminophen). This is known as grand parenting
Grandparenting
-process where new regulations do not apply to those products already on market
-does not need to go through randomized control
What are some potential concerns with a lack of randomized control trials for OTC drugs who’ve been grandfathered
-some older OTC drugs may not be effective (only appropriate manner for testing this would be randomized controlled trial)
-some older OTC drugs have serious toxicities (ex. If acetaminophen had to undergo safety testing would likely not pass as can cause fatal liver toxicity in overdose)
Selection of appropriate OTC drugs
-numerous OTC drugs available to treat a condition but important to select an appropriate OTC drug
Proven efficacy and known toxicity - best drug for condition have proven efficacy and known level of toxicity
Simple formulations and ingredients- best drug have simplest formulation (single ingredient). Most cases formulations that contain multiple drugs have one drug that effective and others of questionable efficacy. List of all ingredients and amounts are provided
Brand vs. Generic - best OTC drug not necessary brand name drug. Generics usually cheaper and just as effective
Appropriate and effective dose - best come in appropriate dosage form (ex. Liquid for children) and have therapeutically efffective dose of active ingredients. Number of OTC products contain too low of a dose to be effective
Internal analgesics
-provide relief from pain
-3 common OTC
Acetylsalicylic acid (ASA)
-generic name for aspirin
-effectively relieves pain (analgesic), inflammation (anti-inflammatory)
-at low doses, it prevents stroke and heart attack
Mechanism of action to inhibits pain, fever and inflammation -> ASA inhibits the synthesis of prostaglandins, which endogenous substances that enhance the mediation of pain and fever, and role in inflammation
Mechanism of action to prevent stroke and heart attack -> ASA inhibits platelet aggregation and hence clot formation
Adverse effects:
-gastric irritation -> most common toxicity, occurring in 2% of population. ASA breaks down the mucosal protective barrier in stomach, leading to irritation and increased bleeding. Serious problem when ASA taken chronically in high doses. A few OTC preparations have tried to address gastric irritation by adding an antacid. In general, most effective to use an analgesic and antacid as seperate entities
Tinnitus -> ringing in ears, tinnitus at high dose
Allergic reactions -> rare but occur. These people may also be allergic to tartazine (yellow food colouring)
Reye’s syndrome -> in children when it is given during fever. Rare but serious illness affecting CNS. As such, acetaminophen drug of choice for fever in children
Acetaminophen
-in over 600 over-the-counter and prescription medicines
-brand name Tylenol
-most widely used OTC analgesic, comprising more than 50% of the market
Mechanism of action -> causes inhibition of prostaglandin synthetases (ie. cyclooxyrgenase I and II) which enzymes responsible for formation of prostaglandins.
Therapeutic use -> effective analgesic and antipyretic (is equal in efficacy to ASA for these 2 effects), however acetaminophen not effective anti-inflammatory medication. Available in liquid preparation so suitable for children and infants. Drug of choice in cases where ASA causes gastric irritation and febrile (have fever) conditions in children and young adults, as acetaminophen not associated with Reye’s syndrome
Adverse effects:
-at therapeutic doses very tolerated, does not cause gastric irritation
-acetaminophen overdose can lead to fatal liver injury
-can case of overdose, individual consume at least 5 - 10 grams (20 tablets)
-individuals with alcohol use disorder or liver disease more susceptible to liver toxicity
-some evidence indicates that liver injury can occur with large therapeutic doses if taken for long time
-one of the issues surrounding acetaminophen is that found in multiple products so individual may overdose by stimulaneously using 2 or 3 cold preparations all containing acetaminophen
Non-steroidal anti-inflammatory drugs (NSAIDs ie. ibuprofen (brand name Advil) and naproxen (brand name aleve)
Therapeutic use ->effective analgesic, antipyretic, anti-inflammatory compounds. 200 mg dose of ibuprofen more effective than 325 mg dose of ASA in a number of conditions, including dental and mensural pain. Move rover. Ibuprofen and napoxen among most effective OCT anti-inflammatory agents available
Adverse effects -> gastric irritation (less than that caused by uncharted ASA), skin rash, dizziness, blurred vision and fluid rentention
Mechanism of action of internal analgesics
-reversible inhibition of synthesis of prostaglandins
-tissue damage occurs -> arachidonic acid released then 1 or 2
1. Converted by enzyme clyooxygenase-1 (or COX-1) into protective porstagladins which involved in many beneficial effects like gastroprotection, platelet aggregation, renal protection, vasodilation and bronchodilation
2. Converted by enzyme cyclooxygenase-2 (COX-2) into imflammatory prostaglandins, causing detrimental effects like inflammation, pain, fever and decreased platelet aggregation
-analgesics like acetyl salicylic acid or aspirin, acetaminophen which is Tylenol, and NSAIDs such as ibuprofen or Advil work by blocking one or both of cyclooxygenase enzymes, decreasing production of prostaglandins involved in inflammation, pain, fever that beneficial but also decrease production of protective prostaglandins which contribute to adverse effects
-do not all block cyclooxygenase enzymes the same way so effects between drugs not all same
Ex. Acetaminophen decreases pain and fever but not help inflammation
*refer to goodnote images
Antihistamines
-treat allergy symptoms like hay fever (ie. allergic rhinitis)
-act by blocking histamine receptors thereby inhibiting the binding of histamine (1 of the main substances released in allergies) to its receptor,decreasing allergy symptoms
-classified into first or second generation agents due to slight differences in pharmacology
1st generation -> ex. Diphenhydramine all causes sedation and drowsiness
2nd generation -> ex. Cetrizine are less sedating and preferred agent
Administered: nasal drops/spray, pills
Drugs for excess stomach acid
-designed to neutralize stomach or decrease stomach acid secretion
-3 main classes
* acid secretion is an active process where protons (H+) are transferred into stomach in exchange for potassium (K+). Process carried out by proton pump
Antacids
-chemically neutralize acids in stomach by an acid-base chemical reaction
-want to hold pH contents at about 4
Systemic ->given orally and absorbed by GI tract ex. Calcium carbonate (Tums) very rapidly neutralize stomach acid and well tolerated generally. Ingestion of large amounts of calcium carbonate can cause hypercalcemia and systemic alkalosis in rare cases
Non-systemic ->given orally but not absorbed so cause systemic alkalosis ex. Aluminum hydroxide coats the mucosal lining of stomach, protecting it from acid. One if more popular antacids from quick onset of action but decreases phosphate absorption, decreasing absorption of other prescription drugs leading to constipation
H2 receptor antagonists
-target acid secretion in stomach
-histamine involved in release of stomach acid
Without H2 receptor antagonist -> when histamine receptors (designated H2) in acid secreting cells of stomach activated, proton pump turned on and acid secretion increased
With H2 receptor antagonist
-block H2 receptors so reduce amount of acid secreted
-agents more effective than antacids
-drugs are free of major adverse effects although skin rashes, headaches and confusion are infrequently reported
*histamine receptors in stomach are distinct from those that cause allergies
Proton pump inhibitors (PPIs)
-target acid secretion in stomach
-ex. Omeprazole
-permanently bind to proton pump, inhibiting acid secretion by 90% or more
-most effective drugs available for suppressing acid secretion
-frequency of adverse effects low and includes diarrhea, headache and abdominal pain
-were only available with prescription until recently
*refer to goodnotes images
Decongestants
-fluid buildup in nasal cavity, causing congestion
-caused by dilation of small blood vessels, which allow fluid to leak from the vessels into space between cells
-can cause constriction of blood vessels, repenting accumulation of fluid and thereby reducing congestion
-a nose drop solution containing 0.5% phenylephrine or an oral tablet of pseudoephedrine are DRUG OF CHOICE!!
-long acting preparations are the best
-long-term use leads to local irritation and chronic rhinitis (congested, runny nose that long lasting) so use shouldn’t exceed 3 days
-other common adverse effects: rebound congestion and potential alternation of blood vessels
Cough suppressants
-cough is complex event involving signals from bronchioles, which possessed by cough centre in medulla of brain
-in general a productive cough (one that clears the airways of muscles) should not be suppressed but a non-productive cough (a dry cough that is one not accompanied by phlegm production) should be suppressed
-2 types of cough suppressants exist
Centerally-acting cough suppressants
-black the processing of information in brain, reducing frequency of cough
-codeine is present in some OTC cough suppressants
-alternative OTC cough suppressant is dextromethorphan hydrobromide (HBr). Effective dose is 20-30 mg every 6 hours. Some contain therapeutic doses and other lower amounts so check label
-ex. Benylin dry cough used to contain 6.5 mg dextromethorphan HBr per dose. Recently updated to contain 15 mg/5 mL or 30 mg per dose
Peripheral cough suppressants
-block nerve endings in throat and bronchioles, inhibiting stimulus to cough
-in these agents, camphor and menthol added to vaporizers or rubbed on throat and chest
-efficacy = questionable. May exert small response to inhibit it peripheral nerves in throat but placebo response likely reason fro any efficacy observed
Cough suppressant of choice
Dextromethorphan HBr
