Pharmaco: RA Flashcards
List the drugs used in RA and their class
Anti-inflammatory agents:
- NSAIDs (short-term pain relief)
- Corticosteroids (low dose bridging therapy)
No role for paracetamol
Conventional Synthetic DMARD (csDMARD)
- Methotraxate
- Sulfasalazine
- Leflunomide
- Hydroxychloroquine
- Ciclosporin
Targeted Synthetic DMARD (tsDMARD)
- Tofacitinib
- Baricitinib
Biologic DMARD (bDMARD)
- Anti-TNF mAb: Infliximab, Adalimumab, Etanercept
- IL-1R antagonist: Anakinra (NA in Sg)
- Anti-CTLA4lg: Abatacept (NA in Sg)
- Anti-CD20: Rituximab
- Anti-IL6 receptor mAb: Tocilizumab
Side effects of glucocorticoids
- Increase CVD risk
- Cataract, glaucoma
- Skin thinning, hirsutism
- Gastric ulcer (if concomitant NSAID)
- Weight gain, fluid retention, Cushing syndrome
- Impaired glucose metabolism, insulin resistance, B-cell dysfunction
- Neuro-psychiatric symptoms, HPA insufficiency
- Osteonecrosis, osteoporosis
- Myopathy
- Infections
[csDMARD - Methotrexate]
Dosage forms
- oral
- SQ
- IM
[csDMARD - Methotrexate]
MOA
Major action:
- Inhibits ATIC enzyme, thereby increasing adenosine levels, activation of adenosine A2a receptors results in anti-inflammatory effects:
- antiproliferative effects on T cells
- inhibition of macrophage functions
- downregulation of pro-inflammatory cytokines, adhesion molecules, chemotaxis, phagocytosis
Minor action:
- inhibits dihydrofolate reductase (DHFR) and thymidylate synthetase, decrease purine synthesis, affect cell replication
[csDMARD - Methotrexate]
Side effects
- GI SEs: N/V/D, Anorexia, Mouth and GI ulcers (stomatitis)
- Hair thinning
- Liver: increase transaminases (therefore need to monitor LFT), hepatic fibrosis, cirrhosis
- Lungs: Fibrosis, pneumonitis
- Haem: bone marrow suppression/myelosuppression, leukopenia
- Derm: photosensitivity, TEN, SJS
[csDMARD - Methotrexate]
Mechanism of side effects
Mechanism: attributed to minor action, at higher dose and long term treatment
MTX inhibits DHFR, reduces levels of tetrahydrofolate and thus decreases synthesis of purines and pyrimidines.
This inhibition leads to a decrease in the production of DNA, RNA and certain amino acids, ultimately disrupting the growth and proliferation of rapidly dividing cells, such as those found in the bone marrow and the walls of GIT, which causes bone marrow suppression and GI disturbances.
[csDMARD - Methotrexate]
How to keep side effects to a minimum?
Concomitant folic acid 5mg/week or folinic acid given 12-24h after methotrexate, can decrease MTX toxicity
Rescue therapy of methotrexate
Folic acid, a synthetic form of the naturally occurring vit B9, helps prevent MTX induced SE by counteracting the reduced levels of tetrahydrofolate
[csDMARD - Methotrexate]
Difference b/w folic acid and folinic acid
Folic acid / Folate
- Cheaper and more commonly used
- However, require high doses as it does not efficiently rescue toxicity
- Folic acid must be converted by DHFR into N5N10-Methylene-FH4 that is essential for cell proliferation (it does not bypass DHFR activity)
Folinic acid (N5-formyl-FH4)
- More expensive
- But more efficient at rescuing MTX toxicity
- Rapidly converted to N5N10-Methylene-FH4 without DHFR activity
[csDMARD - Methotrexate]
(IC16) Contraindications
- Preexisting liver disease
- Immunodeficient syndrome
- Blood dyscrasias
Other precautions/may not prescribe (from the video):
- Liver cirrhosis
- Certain lung conditions
- Pregnant or trying to get pregnant
- Man trying to get someone pregnant
- Significant anemia
- Low WBC
- Breastfeeding
[csDMARD - Methotrexate]
(IC16) Dose adjustment with hepatic or renal impairment
AST/ALT > 3x ULN: 75% of dose
CrCl <50ml/min: 50% of dose
CrCl <30ml/min: avoid use
MTX is 80% excreted renally unchanged
[csDMARD - Methotrexate]
(IC16) DDIs
- NSAIDs/COX-2 inhibitors (incr serum conc. of MTX)
- PPI
- Probenecid
- Vaccines
- Alcohol
[csDMARD - Methotrexate]
(IC16) Use in pregnancy
Teratogenic, embro-fetal toxicity
(exclude pregnancy before starting)
[csDMARD - Methotrexate]
(IC16) Monitoring (side effects and labs)
Side effects:
- Lung: SOB, cough
- GI: N/V, mouth sores, diarrhea
- Liver: jaundice
- Dermatologic toxicity
- Infections
Labs:
- FBC
- LFT (AST, ALT, albumin, bilirubin) - incr transminases, also may affect dosing
- SCr (dose adjustment when CrCl <50ml/min, avoid use when CrCl <30ml/min)
[csDMARD - Sulfasalazine]
MOA
Unknown, but poorly absorbed so may be mediated by effect in gut microflora, leading to changes in immune response:
- Decreased IgA and IgM rheumatoid factors
- Suppression of T and B cells, and macrophages
- Decrease in inflammatory cytokines (e.g., IL-1B, TNF, IL-6)
- (IC16) Modulates leukotrienes, inhibits TNF
[csDMARD - Sulfasalazine]
Metabolism
Metabolized to sulfapyridine (active) + 5-aminosalicylic acid
[csDMARD - Sulfasalazine]
Side effects
- GI: Nausea and vomiting, dyspepsia
- CNS: Headache, dizziness
- Derm: Rash
- Hemolytic anemia
- Neutropenia
- Reversible infertility in men
(IC16)
- Genitourinary: Oligospermia (reversible), urine discoloration
[csDMARD - Sulfasalazine]
(IC16) Contraindications
- Sulfonamide allergies
- Caution in G6PD deficiency
[csDMARD - Sulfasalazine]
(IC16) DDIs
- Iron
- Antibiotics
- Warfarin
[csDMARD - Sulfasalazine]
(IC16) Pregnancy Status
B, may use
[csDMARD - Sulfasalazine]
(IC16) Monitoring: side effects and labs
Side effects
- N/V
- Rash
- Infection
Lab
- FBC
[csDMARD - Leflunomide]
MOA
Inhibits dihydroorotate dehydrogenase
- Decrease in pyrimidine synthesis and growth arrest at G1 phase
- Inhibit T cell proliferation and B cell autoantibody production
- Inhibit NF-kB activation pro-inflammatory pathway
DHODH plays a key role in the de novo synthesis of the pyrimidine
(IC16): decrease lymphocyte action
[csDMARD - Leflunomide]
Metabolism
Rapidly converted to active metabolite, teriflunomide
[csDMARD - Leflunomide]
Side effects
- GI: Diarrhea, nausea
- Liver: incr transaminases (elevation of liver enzymes)
- Derm: Alopecia, skin rash
- CNS: headache
- Haem: myelosuppression
- Weight gain
- Teratogenic
[csDMARD - Leflunomide]
(IC16) Contraindication
- Preexisting liver disease
- ALT > 2x ULN
- Immunodeficient states
[csDMARD - Leflunomide]
Half-life, implications
Leflunomide has very long half-life (detectable years after last dosing)
- Cholestyramine (bile salt binding resin) is used to wash-out the drug (e.g., before pregnancy - since it is teratogenic)
If using Leflunomide, then cholestyramine is a drug interaction (IC16)
[csDMARD - Leflunomide]
(IC16) Dose adjustment in liver impairment
ALT > 2x ULN: avoid use
[csDMARD - Leflunomide]
(IC16) Pregnancy status
Teratogenic
(exclude pregnancy before starting)
[csDMARD - Leflunomide]
(IC16) Monitor SEs and Labs
Side effects:
- Diarrhea
- Hair loss
- Jaundice
- Infection
Labs:
- FBC
- LFTs (AST, ALT, albumin, bilirubin)