Adverse Drug Reactions and Drug Hypersensitivity Reactions questions

The World Health Organization (WHO) defines an Adverse Drug Reaction (ADR) as any response to a drug that is noxious and unintended, and which occurs at doses:

• Normally used in humans for prophylaxis, diagnosis, or therapy

• Memory Note: ADR = Normal dose, bad reaction. If it happens because of an overdose or a mistake, it is a medication error, not a true ADR.

A known, expected, and usually unavoidable secondary pharmacological effect of a drug (like dry mouth from antihistamines) is specifically called a:

• Side effect

• Memory Note: Side effects are expected and predictable based on the drug's mechanism. They can sometimes be beneficial, whereas ADRs are always harmful.

In the Rawlins and Thompson classification of ADRs, reactions that are predictable, dose-dependent, and an extension of the drug's normal pharmacology are classified as:

• Type A

• Memory Note: Type A = Augmented. (Predictable, Dose-dependent, most common). Think "A" for Augmented pharmacology.

A patient taking Insulin injects their normal dose but skips a meal, leading to severe hypoglycemia. This is an example of which type of ADR?

• Type A

• Memory Note: Hypoglycemia from Insulin is an extension of its normal action (lowering blood sugar). Thus, it is a Type A (Augmented) reaction.

ADRs that are completely unpredictable, dose-independent, and occur only in susceptible individuals (like allergies or genetic idiosyncrasies) are classified as:

• Type B

• Memory Note: Type B = Bizarre. (Unpredictable, Allergic, high mortality). Think "B" for Bizarre or Bug-like (Allergy).

Which of the following is a classic example of a Type B adverse drug reaction?

• Anaphylactic shock from Penicillin

• Memory Note: Penicillin allergy is unpredictable and unrelated to the drug's normal action. It is a classic Type B (Bizarre) reaction.

ADRs that occur only after prolonged, long-term, continuous use of a medication are classified as:

• Type C

• Memory Note: Type C = Chronic. Think "C" for Continuous or Chronic use.

A patient develops Cushing's syndrome and osteoporosis after taking oral corticosteroids every day for 5 years. This represents which type of ADR?

• Type C

• Memory Note: Steroid-induced osteoporosis takes years to develop, making it a Type C (Chronic) reaction.

ADRs that become apparent only years after the treatment has stopped, or appear in the children of the patient who took the drug, are classified as:

• Type D

• Memory Note: Type D = Delayed. Examples include carcinogenesis (causing cancer) and teratogenesis (causing birth defects).

The tragedy in the 1960s where pregnant women took a sedative for morning sickness, resulting in babies born with shortened limbs (phocomelia), is a classic Type D reaction. What was the drug?

• Thalidomide

• Memory Note: Thalidomide = Phocomelia (seal limbs). This tragedy led to strict modern FDA drug safety laws.

ADRs that occur when a medication is suddenly stopped or withdrawn too quickly are classified as:

• Type E

• Memory Note: Type E = End of Use. Think "E" for End or Extraction (Withdrawal syndromes).

A patient suddenly stops taking Clonidine and experiences a dangerous spike in blood pressure (rebound hypertension). This is an example of:

• Type E

• Memory Note: Rebound effects upon stopping a drug are classic Type E (End of use) reactions.

ADRs characterized by an unexpected failure of the therapy (the drug simply does not work as intended) are classified as:

• Type F

• Memory Note: Type F = Failure of therapy. Often caused by fake drugs, under-dosing, or severe drug interactions.

A patient taking birth control pills gets pregnant because they were also taking Rifampin, which destroyed the hormones. In the context of ADR classification, this treatment failure is:

• Type F

• Memory Note: Failure of oral contraceptives due to enzyme inducers is a Type F (Failure) reaction.

The science and activities relating to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problem is called:

• Pharmacovigilance

• Memory Note: Vigilance = Watching over. Pharmacovigilance is drug safety monitoring.

The most widely used questionnaire/algorithm designed to determine the likelihood (causality) that a specific drug caused an ADR is the:

• Naranjo Algorithm

• Memory Note: Naranjo = Causality. It gives a score to prove if the drug actually caused the bad reaction (Definite, Probable, Possible, Doubtful).

In causality assessment, the process of deliberately giving the suspected drug to the patient AGAIN to see if the adverse reaction comes back is called:

• Rechallenge

• Memory Note: Rechallenge = Re-giving the drug. A positive rechallenge is strong proof the drug caused the ADR.

The process of stopping the suspected drug to see if the adverse reaction disappears is called:

• Dechallenge

• Memory Note: Dechallenge = Discontinuing the drug. If symptoms go away, it's a positive dechallenge.

An ADR severity level where the patient requires hospitalization, specific medical treatment, or an increase in length of stay is classified as:

• Severe

• Memory Note: Severe = Requires hospitalization or causes permanent harm/disability. Mild requires no antidote; Moderate requires a change in treatment but not hospitalization.

A disease or condition unintentionally caused by medical treatment, a doctor, or a pharmacist is termed a/an:

• B. Iatrogenic disease

• Memory Note: Iatrogenic = "Doctor-caused" or "Treatment-caused" harm.

Any drug that crosses the placenta and causes physical defects in a developing fetus is called a:

• Teratogen

• Memory Note: Terato = Monster in Greek. Teratogens cause birth defects (e.g., Thalidomide, Isotretinoin).

A genetically determined, abnormal, and unpredictable reaction to a drug (such as hemolytic anemia in patients with G6PD deficiency) is called:

• Idiosyncrasy

• Memory Note: Idiosyncrasy = Genetic glitch. It is not an allergy, but a missing enzyme or genetic trait making the drug toxic to that specific person.

Clinical trials conducted after a drug is already approved and available on the market, used to detect rare ADRs, are part of:

• Phase IV Post-Marketing Surveillance

• Memory Note: Phase IV = Real-world watching. This is where most rare ADRs (Type B) are finally discovered.

Which international organization manages the global database of adverse drug reaction reports?

• WHO Uppsala Monitoring Centre (UMC)

• Memory Note: Uppsala (in Sweden) is the worldwide headquarters for collecting ADR reports.

In the Philippines, healthcare professionals report adverse drug reactions to which regulatory body?

• FDA (Food and Drug Administration) Pharmacovigilance Unit

• Memory Note: The FDA handles drug safety, recalls, and ADR reports in the country.

A drug allergy is an adverse reaction caused by the body's overreaction to a drug involving the:

• Immune system

• Memory Note: Allergy = Immune System mistake. The body attacks the drug as if it were a dangerous virus or bacteria.

The widely used system that divides immune hypersensitivity reactions into four types (Type I, II, III, IV) is the:

• Gell and Coombs Classification

• Memory Note: Gell and Coombs = The 4 types of allergies. (Do not confuse with Rawlins and Thompson which is A-F for general ADRs).

Type I Hypersensitivity is an immediate, life-threatening allergic reaction mediated by which specific antibody?

• IgE

• Memory Note: Type I = IgE. (Think "E" for Emergency).

The most severe and potentially fatal form of a Type I hypersensitivity reaction is:

• Anaphylactic shock

• Memory Note: Anaphylaxis involves airway swelling and a massive drop in blood pressure. It happens within minutes.

In a Type I allergic reaction, IgE antibodies bind to mast cells, causing them to break open (degranulate) and release massive amounts of which inflammatory chemical?

• Histamine

• Memory Note: Histamine causes the itching, hives, and airway constriction in allergies.

The absolute first-line, life-saving drug of choice for treating anaphylactic shock is:

• Epinephrine (Adrenaline)

• Memory Note: Epinephrine saves lives in minutes. Antihistamines and steroids are too slow for anaphylaxis; they are secondary treatments.

What is the standard route of administration for Epinephrine in treating anaphylaxis?

• Intramuscular (IM) injection into the outer thigh

• Memory Note: IM injection in the anterolateral thigh provides the fastest, safest absorption.

Type II Hypersensitivity involves antibodies (IgG or IgM) mistakenly attacking the patient's own blood cells because a drug has attached to them. This is called:

• Cytotoxic Hypersensitivity

• Memory Note: Type II = Cyto-toxic (Cell-killing). The immune system literally bursts the patient's red blood cells (Hemolytic anemia).

A patient taking Methyldopa or Penicillin develops Drug-Induced Hemolytic Anemia. This is an example of:

• Type II Hypersensitivity

• Memory Note: Hemolytic Anemia = Red blood cells destroyed = Type II (Cytotoxic).

Type III Hypersensitivity occurs when drugs and antibodies form large clumps (complexes) that get stuck in tissues and blood vessels, causing massive inflammation. This is known as:

• Immune-Complex Hypersensitivity

• Memory Note: Type III = Immune Complexes. The clumps get stuck in joints, kidneys, and skin.

A classic example of a Type III Hypersensitivity reaction that presents with fever, joint pain (arthralgia), and swollen lymph nodes 1-2 weeks after taking a drug is:

• Serum Sickness

• Memory Note: Serum Sickness = Type III. It takes time for the immune complexes to form and get stuck.

Type IV Hypersensitivity is unique because it does NOT involve antibodies. Instead, it is mediated by:

• T-cells (T-lymphocytes)

• Memory Note: Type IV = T-cells. It is the only type of hypersensitivity that doesn't use antibodies (IgG, IgE, etc.).

Type IV Hypersensitivity takes 48 to 72 hours to develop after exposure to the drug. Because of this, it is commonly called:

• Delayed-Type Hypersensitivity (DTH)

• Memory Note: Type IV = Delayed (DTH). (Think IV = 4 = 48+ hours).

A patient applies a topical antibiotic cream and 2 days later develops a severely itchy, blistering rash exactly where the cream was applied. This Type IV reaction is called:

• Contact Dermatitis

• Memory Note: Contact Dermatitis (like poison ivy or cream allergies) is a classic Delayed T-cell Type IV reaction.

Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are severe, life-threatening blistering skin peelings caused by drugs. They are extreme variants of which hypersensitivity?

• Type IV

• Memory Note: SJS/TEN = Severe Type IV. T-cells attack the skin, causing the epidermis to completely detach.

The medical term for "hives" (raised, intensely itchy red welts on the skin common in Type I allergies) is:

• Urticaria

• Memory Note: Urticaria = Hives. (Pruritus just means itching).

Most drugs are too small to trigger an immune response on their own. They must first bind to a carrier protein in the blood to become an allergen. A small molecule that does this is called a:

• Hapten

• Memory Note: Hapten = "Half-antigen". It needs a protein partner to become a full allergy trigger. (Penicillin is a famous hapten).

A patient has a severe anaphylactic allergy to Penicillin. The pharmacist must avoid giving them which other class of antibiotics due to a high risk of cross-reactivity?

• Cephalosporins

• Memory Note: Penicillins and Cephalosporins both have a Beta-Lactam ring. If the immune system hates the ring in one, it might attack the other (cross-reactivity).

A reaction that mimics anaphylaxis (causes histamine release and hives) but does NOT involve the immune system or IgE antibodies is called a:

• Pseudoallergy (Anaphylactoid reaction)

• Memory Note: Pseudo = Fake. It looks exactly like an allergy, but the drug directly breaks open mast cells without using the immune system.

A patient receiving IV Vancomycin suddenly develops intense flushing, redness, and itching of the face, neck, and upper torso. This famous pseudoallergy is called:

• Red Man Syndrome

• Memory Note: Vancomycin = Red Man Syndrome. This is a pseudoallergy caused by direct histamine release.

How is Red Man Syndrome prevented when administering Vancomycin?

• By infusing the IV very slowly (over at least 60 minutes)

• Memory Note: Slow infusion prevents direct mast cell rupture. (True allergies happen regardless of infusion speed; pseudoallergies are rate-dependent).

Patients with a known "Sulfa" allergy should strictly avoid which of the following common antibiotics?

• Cotrimoxazole (Sulfamethoxazole/Trimethoprim)

• Memory Note: Cotrimoxazole (Bactrim/Septra) contains Sulfamethoxazole. It is a massive trigger for SJS in sulfa-allergic patients.

In the event of a mild Type I allergic reaction (just itching and hives, NO breathing problems), the primary pharmacological treatment is:

• Antihistamines

• Memory Note: Mild allergy = Antihistamines. (Save Epinephrine for anaphylaxis/breathing problems).

Medical professionals sometimes use Corticosteroids (like Prednisone or Hydrocortisone) in allergic reactions to:

• Prevent delayed or secondary inflammatory responses hours later

• Memory Note: Steroids take hours to work. They are given to stop the allergy from coming back the next day, not to fix the immediate emergency.

A clinical procedure where a patient is given very tiny, gradually increasing doses of a drug they are allergic to (like Penicillin) until their immune system builds a temporary tolerance is called:

• Desensitization

• Memory Note: Desensitization = Forcing the body to accept the drug. It is only done when the drug is absolutely necessary (like Penicillin for neurosyphilis) and must be done in an ICU.