Systemic Medications Flashcards
MTX: Name 2 health Canada approved uses for derm
PsO/PsA
CTCL-advanced
Name 8 contraindications to MTX
Absolute: pregnancy/lactation, hypersensitivity
Relative: severe renal impairment, chronic liver disease, immunodeficient, cytopenias, etoh, Tb, chronic or active Hep B/C
What 4 enzymes does MTX inhibit?
Anti-folate:
1. Dihydrofolate reductase
2. Thymidylate synthase
Anti-inflammatory:
3. AICAR transformylase
4. Ecto-5’nucleotidase
What does dihydrofolate reductase do?
What does thymidylate synthase do
folic acid–> tetrahydrofolate via DHFR
Tetrahydrofolate–> DNA precursors via thymdylate synthase
What is the MOA generally of MTX? Name 2 pathways
- Folate inhibitor–> Inhibits DNA synthesis
- Anti-inflammatory–> increases adenosine which is anti-inflammatory
Name 10 non-skin side effects of MTX
Lungs: Acute and chronic interstitial pneumonitis
Liver: Acute hepatotoxic and fibrosis
GI: N/V, diarrhea, oral ulcers
Renal: Nephrotoxicity in setting renal impairment
Blood: Cytopenias
Reproductive: Teratogen, miscarriage
Infection: Hep B/C reactivation, TB, increased risk infections
Malignancy: KC and lymphoma
Name 4 skin side effects MTX
Radiation/sunburn recall
Skin cancer
Alopecia
SJS/TEN
Oral ulcers
What baseline tests do you need before starting MTX?
BLAK BaTH
Blood-CBC
Liver-LFT/LE
Kidney
B-HCG
Tb
HepB/C
What monitoring is needed for MTX
CBC + LE/LFTs + Cr q1week x 1 month
q1 months x 3 months
q4-6 months
What is the dosing range for MTX?
Folic acid?
10 mg po qweekly
(10-25 mg qweekly)
Folic acid 1 mg po daily on non MTX days
Name 6 risk factors for pancytopenia in MTX
FARSIIDE
Folic acid-lack
Albumin <30
Renal dysfunction
Septra/NSAIDS
Illness
Initial 4-6 weeks
Infection
Daily MTX
Elderly
How long can you wait after MTX before conceiving?
Females 1 ovulatory cycle
Males 3 months
What are 2 benefits of folate
- Reduce risk pancytopenia
- May reduce risk hepatotoxicity
Name 3 pathways of drug interactions with MTX and 2 examples of each?
- Increases levels by binding to albumin
- Decreases renal excretion
- Also inhibits folate
-dapsone
Name 3 pathways of drug interactions with MTX and 2 examples of each?
- Increases drug levels
-NSAIDS/ASA, Septra, phenytoin/phenothiazine, tetracycline - Hepatotoxic: etoh, retinoids
- Also inhibits folate
-sulfa drugs (dapsone, sulfasalzine, septra)
*TAPAS
Tetracycline
Aggrenox (dypyramidole)
phenothiazine/phenytoin, ASA/NSAIDS
sulfa
