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PHY Flashcards

1
Q

Pharmacokinetics

Pharmacodynamics

A

Pharmacokinetics: what the body does to the drug

Pharmacodynamics: what the drug does to the body

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2
Q

Clearance

A

Volume of plasma cleared of a drug per unit time

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3
Q

Half-life

A

Time taken for drug concentration to decline to half its original value.

Depends on volume of distribution and clearance

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4
Q

Volume of Distribution

A

Volume into which a drug appears to distribute.

High for lipid-soluble drugs

Low for water soluble drugs

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5
Q

First Order Kinetics

A

Clearance of drug is always proportional to plasma concentration.

Most drugs are in this category

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6
Q

Zero Order Kinetics

A

Clearance of drug not always proportional to plasma concentration.

Saturation of metabolism → constant rate of elimination regardless of plasma levels.

E.g. phenytoin, salicylates, ethanol

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7
Q

Bioavailability

A

Percentage of the dose of a drug which reaches the systemic circulation.

100% for IV administration

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8
Q

Multiple Dosing

A

If a drug given at intervals the concentration will reach a steady state in ~ 5 half-lives.

Loading dose: ↓ time needed to reach a steady state.

Useful if long or short half life.

Phenytoin, digoxin, amiodarone, theophylline

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9
Q

Therapeutic Drug Monitoring

Indicated when lack of drug efficacy, possibility of poor compliance, suspected toxicity, or prevention of toxicity.

A 
􏰀 Aminoglycosides (essential)
􏰀 Vancomycin (essential)
􏰀 Li (essential)
􏰀 Phenytoin
􏰀 Carbamazepine
􏰀 Digoxin
􏰀 Ciclosporin
􏰀 Theophylline
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10
Q

First Pass Metabolism

A

Metabolism and inactivation of a drug before it reaches the systemic circulation.

i.e. pre-systemic elimination

Occurs in gut wall and liver

E.g. propranolol, verapamil, morphine, nitrates

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11
Q

Pathways of Drug Metabolism and Elimination

A

Excrete unchanged by the kidney (e.g. furosemide)

Phase 1 metabolism then renal excretion

Phase 2 metabolism then renal excretion

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12
Q

Phase 1 Metabolism

A

Creation of reactive, polar functional groups

  • Oxidation: usually by CyP450 system
  • Reduction and hydrolysis
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13
Q

Phase 2 Metabolism

A

Production of polar compounds for renal elimination

Either the drug or its phase 1 metabolite

  • Conjugation reactions
  • Glucuronidation, sulfonation, acetylation, methyl
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14
Q

Cytochrome P450 System

A

Most important system of phase 1 metabolism

> 11 subtypes

CyP3A4

  • Most important subtype
  • ≥ 30% of drugs: CCBs, β-B, statins, benzos

CyP2D6
- Second most important
- ≥20% of drugs: antidepressants, some β-B,
opiates

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15
Q

List of pro-drugs.

A

L-Dopa → dopamine

Enalapril → enalaprilat

Ezetimibe → ez-glucuronide

Methyldopa → α-methylnorepinephrine

Azathioprine → 6-mercaptopurine (by XO)

Carbimazole → methimazole

Cyclophosphamide

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16
Q

Adverse drug reactions (ADR)

A

Type A

  • Common, predictable reactions
  • Dose-related (but may occur @ therapeutic doses)
  • Consequence of known pharmacology of the drug

Type B

  • Rare, idiosyncratic reactions
  • Usually not dose-related
  • E.g. allergies and pharmacogenetic variations

Long-Term ADR

  • Dependence, addiction
  • Withdrawal phenomena
  • Adaptive changes: e.g. tardive dyskinesia

Delayed ADR

  • Carcinogenesis
  • Teratogenesis
17
Q

4 types of allergies

A

Type 1: anaphylaxis
- Penicillins, contrast media

Type 2: cytotoxic antibodies

  • E.g. causing haemolysis
  • Penicillins, cephalosporins, oral hypoglycemics
  • Methyldopa

Type 3: immune complexes

  • Serum sickness-like reaction
  • Penicillins, sulphonamides

Type 4: cell-mediated

  • Contact dermatitis
  • Topical abx
  • Antihistamine cream
18
Q

ADR caused by the following?

  • Carbamazepine
  • Cyclophosphamide
  • Chlorpropamide
  • SSRIs
  • TCAs
A

SIADH

19
Q

ADR caused by the following?

  • Spironolactone
  • Digoxin
  • Verapamil
  • Cimetidine
  • Metronidazole
A

Gynaecomastia

20
Q

ADR caused by the following?

  • Bleomycin
  • Busulfan
  • Amiodarone
  • Nitrofurantoin
  • Sulfasalazine
  • Methotrexate
  • Methysergide
A

Pulmonary Fibrosis

21
Q

ADR caused by the following?

  • Isonazid
  • Vincristine
  • Amiodarone
  • Nitrofurantoin
  • Penicillamine
A

Peripheral Neuropathy

22
Q

Drugs that increase QTc

A
  • Fluoroquinolones: cipro
  • Venlafaxine
  • Neuroleptics: phenothiazines, haldol
  • Macrolides
  • Anti-arrhythmics 1a/III: quinidine, amiodarone, sotalol
  • TCAs
  • Histamine antagonists
23
Q

ADR caused by the following?

  • Clavulanic acid: may be delayed
  • Fluclox: may be delayed
  • Erythromycin
  • Sulfonylureas (glibenclamide)
  • OCP
  • Tricyclics
  • Chlorpromazine, prochlorperazine
A

Cholestasis: decrease in bile flow

24
Q

Which drugs cause hepatocellular damage?

A
  • Paracetamol
  • Valproate, phenytoin, carbamazepine
  • Halothane
  • Methotrexate
  • Statins
  • Rifampicin, isoniazid, pyrazinamide
25
Q

Drugs that cause bone marrow toxicity

A

Pancytopenia /aplastic anaemia:

  • Cytotoxics
  • Phenytoin
  • Chloramphenicol
  • Penicillamine
  • Phenothiazines
  • Methyldopa

Neutropenia:

  • Carbamazepine
  • Carbimazole
  • Clozapine
  • Sulfasalazine

Thrombocytopenia:

  • Valproate
  • Salicylates
  • Chloroquine
26
Q

Extrapyramidal side effects are caused by?

Parkinsonism
Acute dystonia
Akathisia
Tardive dyskinesia

A

Typical antipsychotics

Rarely: metoclopramide, prochlorperazine

Esp. in young women

Dyskinesias and dystonias are common with anti-
parkinsonian drugs.

Mechanism:

  • D2 block in the nigrostriatal pathway
  • Excess AChM (hence effect of anti-AChM)
27
Q

Parkinsonism

A
  • Occurs w/i months
  • Commoner in the elderly
  • Bradykinesia tremor, rigidity

Treatment:
- Procyclidine (anti-AChM)

28
Q

Acute Dystonia

A
  • Occurs w/i hrs-days of starting drugs
  • Commoner in young males
  • Involuntary sustained muscle spasm
  • E.g. lock jaw, spasmodic torticollis, oculogyric crisis

Treatment:
- Procyclidine

29
Q

Akathisia

A
  • Occurs w/i days-months
  • Subjective feeling of inner restlessness

Treatment:
- Propranolol (crosses BBB)

30
Q

Tardive dyskinesia

A

Rhythmic involuntary movements of head, limbs and trunk.

  • Chewing, grimacing
  • Protruding, darting tongue
  • Occur in 20% of those on long-term neuroleptics (yrs)

Treatment:

  • Switch → atypical neuroleptic
  • Clozapine may help
  • (procyclidine worsens symptoms)
31
Q

Indirect drug interactions

A

Diuretics and steroids → Increase risk of digoxin toxicity via low K+

NSAIDs + warfarin → Increased risk of GI bleed

Abx + warfarin → Increase bleeding risk (Abx kill GI microflora that make vit K)

32
Q

P450 Inducers

Mnemonic: CRAP GPS

A
  • Carbamazepine
  • Rifampicin
  • Alcohol (chronic)
  • Phenytoin
  • Griseofulvin
  • Phenobarbital
  • St. John’s Wort
33
Q

Important Drugs Metabolised by P450

A
  • Ciclosporin
  • Oral contraceptive pill
  • Warfarin
  • Epileptic drugs: phenytoin, CBZ
  • Statins
  • Theophylline
34
Q

P450 Inhibitors

Google SICKFACE .COM

A
  • Grapefruit juice
  • Sodium valproate
  • Isoniazid
  • Cimetidine
  • Ketoconazole
  • Fluconazole
  • Alcohol (binge)
  • Ciprofloxacin
  • Erythromycin/Clarithromycin
  • Chloramphenicol
  • Omeprazole
  • Metronidazole
35
Q

Extrapyramidal side effects list

A

Akinesia - finding it hard to start a movement

Akathisia - finding it hard to keep still, and with
‘an inner feeling of restlessness’

Dyskinesia – unusual movements or twitches
(usually of the face) that may keep on
repeating themselves

Oculogyric crisis – unusual eye movements,
most commonly with the eyes turning upwards

Parkinsonism – some of the symptoms look like
someone with Parkinson’s disease e.g. tremor
or stiffness

P (19 decks)

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