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Pharmacology > Antimetabolites > Flashcards

Antimetabolites Flashcards

1
Q

What is the MOA of methotrexate?

A

Folate antagonist/blocks cell division
- inhibits dihydrofolate reductase
- inhibits thymidylate synthetase

Anti-inflammatory (adenosine)

Has effects on T cells and keratinocytes

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2
Q

What are the contraindications to methotrexate?

A

Hypersensitivity
Pregnancy/lactation
Severe hepatic or renal disease
EtOH abuse
Active/recent infection or malignancy
Cytopaenias
Unreliable patient

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3
Q

What are the drug interactions of methotrexate?

A
  1. Other folate inhibitors eg TMP, dapsone, sulfonamides
  2. Renal: NSAIDs, phenytoin, tetracyclines
  3. Hepatotoxicity: EtOH, retinoids
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4
Q

What are the contraception requirements for methotrexate?

A

Females: negative pregnancy test within 1 week of starting, off the medication for at least 1 month before conceiving

Males: no requirements

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5
Q

What are the adverse effects of methotrexate?

A

GI effects
Mucositis/stomatitis
Alopecia
Photosensitivity/toxicity
Malaise, fatigue
Haem: Cytopaenias
Resp: pneumonitis/fibrosis
Infection & malignancy
Abortifacient

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6
Q

What is the baseline and ongoing monitoring requirement for methotrexate?

A

Baseline
Complete Hx & exam to exclude infection and malignancy
FBC, UEC, LFT, BhCG, BSL, lipids
Immunosuppression screen
Fibroscan
Vaccination catch up

Ongoing
BMI/waist circumference every 6 months
FBC, UEC, LFT every 2 weeks for 2 months and then every 3 months
BSL, lipids every 6 months
Fibroscan every 1-3 years

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7
Q

What are the contraindications of azathioprine?

A

Hypersensitivity
Pregnancy/lactation
TMPT deficiency
Severe hepatic or renal impairment
Active/recent infection or malignancy
Prior use of alkylating agent
Unreliable patient

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8
Q

What are the drug interactions of azathiprine?

A
  1. Allopurinol, febuxostat (XO inhibitors)
  2. Methotrexate (incr. 6-MP)
  3. ACE inhibitors (incr. risk of leukopenia)
  4. Other immunosuppressants
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9
Q

What are the adverse effects of azathioprine?

A

GI effects, transaminitis, pancreatitis
Cytopaenias
Increased risk of infection & malignancy
Hypersensitivity syndrome
Teratogenicity

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10
Q

What is the MOA of azathioprine?

A

Purine analogue

Affects numbers / function of
- T cells
- B cells
- antigen-presenting cells

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11
Q

What are the 3 pathways of metabolism for azathioprine?

A
  1. TPMT (inactive)
  2. Xanthine oxidase (inactive)
  3. HGPRT (active)
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12
Q

How is azathioprine dosed based on TPMT levels?

A
  1. Normal 2-2.5mg/kg
  2. Heterozygous 1-1.5mg/kg
  3. Homozygous - Do NOT use
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13
Q

What baseline and ongoing monitoring is required for azathioprine?

A

Baseline
Complete Hx & exam incl. skin & LNs
TPMT level
FBC, UEC, LFT, BhCG,
Immunosuppression screen
Age appropriate malignancy screen
Contraception
Consider PJP prophylaxis

Monitoring
FBC, LFT every 2 weeks for 2 months and then every 3 months
* more frequent if increase in dose or hepatic or renal disease
FSE & LN every 6 months

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14
Q

What are the contraindications to mycophenolate?

A

Hypersensitivity
Pregnancy/lactation
Gastritis/PUD/GI bleed
Severe hepatic, renal or cardiopul dz
Unreliable patient

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15
Q

What is the MOA of mycophenolate?

A

Inhibits inosine monophosphate dehydrogenase (enzyme involved in purine metabolism)

Cytotoxic to lymphocytes made by “de novo” pathway

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16
Q

What are the adverse effects of mycophenolate?

A

GI effects
Gastritis/PUD/GI bleed
GU: urgency, frequency, dysuria
CNS: headache, tinnitus, weakness
Cytopaenias
Infection & Malignancy
Teratogenic

17
Q

What are the drug interactions of mycophenolate?

A

Reduces MMF: PPI, antacids, iron
Increased MMF: probenecid, aciclovir
Reduced enterohepatic recirculation: cholestyramine
Other immunosuppressants

18
Q

What baseline and ongoing monitoring is required for mycophenolate?

A

Baseline
Complete Hx and exam
FBC, UEC, LFT, BhCG
Immunosuppression screen
Vaccinations catch up
Age appropriate malignancy screen
Contraception for 1 month prior and 6 months post

Monitoring
*FBC, UEC, LFT every 2 weeks for 1 month and then every 3 months

19
Q

What is the MOA of cyclosporin?

A
  1. Inhibits IL-2 production —> reduced T cell proliferation
  2. Reduced activity of NFAT1 —> inhibits T cell proliferation
  3. Inhibits IFN-gamma production —> reduced keratinocyte proliferation
  4. Binds to HSP 56 —> reduced pro inflammatory cytokines eg IL-1, TNF alpha
20
Q

What are the drug interactions for cyclosporin?

A
  1. CYP3A4 substrates/inducers/inhibitors
  2. Renotoxics: NSAIDs, aminoglycosides, diuretics
  3. Spironolactone (Hyperkalemia)
  4. Lovastatin (Myopathy)
  5. Other immunosuppressants
21
Q

What are the adverse effects of cyclosporin?

A
  1. Renal dysfunction
  2. Hypertension
  3. Hypercholesterolemia
  4. Hyperkalemia
  5. Hyperuricemia
  6. GI effects
  7. Gingival hyperplasia, hypertrichosis
  8. Other: headache, parenthesia, tremor, myalgia/arthralgia
  9. Infection
  10. Malignancy (NMSC, lymphoma)
22
Q

What baseline and ongoing monitoring is required for cyclosporin?

A

Baseline
Complete Hx & exam (rule out infection and malignancy)
Blood pressure (2 separate occasions)
FBC, UEC, CMP, LFT, urate, lipids, BhCG
Immunosuppression screen
Vaccinations catch up
Age appropriate malignancy screening

Ongoing
Weekly: Blood pressure
Fortnightly: UEC, Urinalysis
Monthly: FBC, CMP, LFT, urate, lipids
6 monthly: skin exam incl. LNs

23
Q

How is dosing of cyclosporine affected by renal impairment?

A

Cyclosporine is contraindicated in renal disease

24
Q

What are MEK inhibitors used for in dermatology?

A

BRAF +ve malignant melanoma

25
Q

What are the contraindications to MEK inhibitors?

A

Hypersensitivity
Pregnancy/lactation
Children <18 years
Severe cardiac/hepatic/renal disease

26
Q

What are the adverse effects of MEK inhibitors?

A

Acne, xerosis, itch, rash, stomatitis, paronychia
GI effects
Hypertension, cardiomyopathy
ILD
VTE
Lymphoedema
Retinal detachment

27
Q

What baseline and ongoing monitoring is required for MEK inhibitors?

A

Full hx and exam inc. skin
FBC, UEC, LFT, urinalysis, BhCG, ECG

28
Q

What is the rate of hypertension in patients treated with cyclosporin?

A

20-55%

29
Q

When does hypertension develop in patients treated with cyclosporine?

A

First few weeks

30
Q

True or false,
Nephrotoxicity arising from cyclosporine use is usually reversible

A

True

Pharmacology (13 decks)

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