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Year 2 LCRS Pharmacology > 23: Adverse Drug Reactions > Flashcards

23: Adverse Drug Reactions Flashcards

1
Q

How can you classify adverse drug Reactions?

A

According to their

  • onset
  • severity and
  • Type A-E
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2
Q

How can you classify ADR (adverse drug Reactions) according to their Onset

A
  • Acute
    • Within 1 hour
  • Sub-acute
    • 1 to 24 hours
  • Latent
    • > 2 days
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3
Q

How can you classify ADR according to their severity?

A
  • Mild
    • requires no change in therapy
  • Moderate
    • requires change in therapy, additional treatment, hospitalisation
  • Severe
    • disabling or life-threatening
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4
Q

What are the main characteristics and problems with Severe ADR?

A
  • Results in death
  • Life-threatening
  • Requires or prolongs hospitalisation
  • Causes disability
  • Causes congenital anomalies
  • Requires intervention to prevent permanent injury
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5
Q

What are type A Adverse Drug Reactions?

A
  • extension of pharmacologic effect –> when you look at effect you can kind of guess what the ADR will be
  • usually predictable and dose dependent
  • responsible for at least two-thirds of ADRs
    • e.g., atenolol and heart block, anticholinergics and dry mouth, NSAIDS and peptic ulcer
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6
Q

Explain the characteristics of Type B ADRs

A
  • idiosyncratic (only occur in some people with unknown cause) or immunologic reactions
    • includes allergy and “pseudoallergy”
  • rare (even very rare) and unpredictable
  • e.g., chloramphenicol and aplastic anemia, ACE inhibitors and angioedema

Many serious ADRs are totally unexpected eg Herceptin and cardiac toxicity –> Show how little we often know about drug mechanisms

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7
Q

Explain the Characteristics of Type C ADRs

A

•Type C

  • associated with long-term use
  • –> involves dose accumulation
  • e.g., methotrexate and liver fibrosis, antimalarials and ocular toxicity
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8
Q

Explain the characteristics of Type D ADRs

A

Delayed effects (sometimes dose independent)

  • carcinogenicity (e.g. immunosuppressants)
  • teratogenicity (disturb embriological developemnt) (e.g. thalidomide)
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9
Q

Explain the Characteristics of Type E ADR

A

When stopping the drug:

  • Withdrawal reactions
    • Opiates, benzodiazepines, corticosteroids
  • Rebound reactions
    • When stoping the drug the situation will be worst than the time you started
      • Clonidine in HTN, beta-blockers, corticosteroids
  • “Adaptive” reactions
    • Neuroleptics (major tranquillisers) (drug might develop e.g. a tremor as reaction to drug that gets worse when withdrawling the drug again)
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10
Q

How can you classify the different types of ADR (MNemonic for the different types

A

A Augmented pharmacological effect

B Bizarre

C Chronic

D Delayed

E End-of-treatment

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11
Q

What are pseudoallergies?

Which Role do they play in the ADR?

A

Pseudoallergies are no allergies (not IgE mediated) but pharmacological interactions –> might e.g. lead to a direct stimmulation of mast cells (no sensitisation required)

E.g.

  • Aspirin/NSAIDs – bronchospasm
  • ACE inhibitors – cough(15-20%)/angioedema (1%), not immunulogical and normally less severe than anaphylaxis (but in case of angiooedema: might also be fatal)
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12
Q

Explain the correlation between numbers of perscribed drugs and ADR

A

Not surprising: the more Drugs are perscibred, the more ADR can be seen

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13
Q

Which Drugs Classes cause the most ADRs?

Why?

A

Mainly because they are very common drugs (commonly perscribed so high numbers but relativels low incidence)

  • Antibiotics
  • Antineoplastics*
  • Anticoagulants
  • Cardiovascular drugs*
  • Hypoglycemics
  • Antihypertensives
  • NSAID/Analgesics*
  • CNS drugs*

*account for two-thirds of fatal ADRs

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14
Q

How can you detect ADRs?

A
  • Subjective report
    • patient complaint
  • Objective report:
    • direct observation of event
    • abnormal findings
      • physical examination
      • laboratory test
      • diagnostic procedure
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15
Q

Why can drugs that casue ADR still be marketed?

A
  1. Often ADR are not known before marketing (expecially rare ones –> sample size just are not big enough)
  2. (still might have necessary effect)
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16
Q

What is the yellow card scheme?

A

A way to detect and Monitor ADR

  • voluntary report of
  • serious side effect for estabished drugs
  • any ADR for drugs in black triange (<2 years after licensing)
    • ADR can be reported by everyone
17
Q

When a ADR in a newly perscribed (or established drug) is suspected: what would be the further process of investigating this?

A
  1. Suspected ADR
  2. Try to confirm (high propability)
  3. Estimate frequency
  4. Accordingly: inform perscriber (or might even lead to withdrawl from market)
18
Q

What are the problems that might occur in the assesing of the incidence of Drug-Drug interactions?

A
  • very complicated to determine (basically impossible/unknown in complicated patients)
  • Difficulty in assessing OvetTheCcounter and herbal drug therapy use
  • Therefore
    • Lack of availability of comprehensive databases
    • Data for drug-related hospital admissions do not separate out drug interactions, focus on ADRs
19
Q

What types of Drug-Drug interactions might occur?

A

There might be:

  • Pharmacokinetic
    • e.g. receprot site occupancy
  • Pharmacodynamic and
    • ADME
  • Pharmaceutical drug-drug interactions
    • outside the body
20
Q

What is a pharmaceutical Drug-Drug interaction?

A

drugs interacting outside the body (mostly IV infusions) –> when giving several medications into an IV infusion bag–> might interact with each other

21
Q

What are pharmacodynamic drug drug interactions?

A

They alther the effects at the site of action:

  • Additive (Drug1+Drug2= Effects of Drug 1+2) (overlapping toxicities of Benzodiazepines and E2)
  • synergistic (parts are working together to enhance their effect) (Drug 1+Drug3= Effects of Drug 1+3 +additional effects) (e.g. ABX)
  • or antagonistic effects from co-administration of two or more drugs (amitriptyline and acetylcholinesterase inhibitors)
22
Q

What are the general sites where Pharmacoinetic Drug interactions can occur?

A

Interactions can change the … of one or more drugs

  • Alteration in absorption
  • Protein binding effects
  • Changes in drug metabolism
  • Alteration in elimination
23
Q

Explain how Drug-Drug interactions can lead to an alteraltion in Absorbtion

A

E.g. Chelation

–Irreversible binding of drugs in the GI tract that then form e.g. an insoluble precipitate

–Tetracyclines, quinolone antibiotics - ferrous sulfate (Fe+2), antacids (Al+3, Ca+2, Mg+2), dairy products (Ca+2)

24
Q

Explain how protein binding interactions can lead to drug-drug interactions

A

Plasma Protein Drugs can be displaced from other drugs which bind to the same PP –> increase the active dose

  • (thougnt to be very important put turns out they are not actually)
  • But which is relevant: E.g. Warfarin
25
Q

Explain how Drug Drug interactions may interefere with Drug Metabolism

A

E.g. via using the same enzymes for Metabolism. Expecially important: Cytochrome P450

  • Though most drugs are metabolised by several P450 enzymes, if other isoforms are inhibited the active one might still metabolise more but no guarantee
  • There are known Enzyme Inhibitors and Ezyme enhancers
26
Q

Name some P450 inhibitors

A
  • Cimetidine (anti-histaminicum)
  • Erythromycin and related antibiotics
  • Ketoconazole (anti-fungals)
  • Ciprofloxacin and related antibiotics
  • Ritonavir and other HIV drugs
  • Fluoxetine and other SSRIs
  • Grapefruit juice
27
Q

List typical P450 emzyme enhancers

A
  • Rifampicin (ABX)
  • Carbamazepine (anticonvulsant)
  • (Phenobarbitone)(barbiturate)
  • (Phenytoin) (anti-convulsive)
  • St John’s wort (hypericin)
28
Q

How fast du enzmyme inhibitors or P450 enhancers normally take to show their effect

A

(Not necessarily wanted but)

Inhibition is very rapid

Induction takes hours/days

29
Q

Explain the role of drug-drug interactions in excretion

A

Almost always in renal tubule

Can be wanted and unwanted

  • probenecid and penicillin (good) –> prolong effect and concentration of Penicillin in body (wanted when it was expensive)
  • lithium and thiazides (bad) (might lead to lithium poisoning
30
Q

Name some examples where drug-drug interactions are wanted and therapeutically ecploited

A
  • levodopa + carbidopa
  • ACE inhibitors + thiazides

penicillins + gentamicin

salbutamol + ipratropium

31
Q

Who runs the yellow card scheme?

A

Medicines and Healthcare Products Regulatory Agency (MHRA)

32
Q

How many people do you need to see to see 1) one 2) three ADR with an incidence of 1:1,000

A

1) one= 3.000 (x3)
2) three: 6.500 (x6.5)

Year 2 LCRS Pharmacology (38 decks)

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