Pharmacology 2 Flashcards
Description and mechanism of action of prednisone
Immunosuppressive oral corticosteroid; most-prescribed oral corticosteroid. Used for TX of autoimmune disorders, allograft rejection, asthma, inflammatory bowel disease, rheumatoid arthritis, and other inflammatory states.
Prodrug of prednisolone, must be metabolized in vivo to prednisolone. Acts via nuclear receptors to modulate gene expression.
Anti-inflammatory: represses COX-2 expression; ↓ cytokine production, decreased formation and release of endogenous inflammatory mediators; causes apoptosis of eosinophils.
Pharmacokinetics of prednisone
Given PO, doses range from 5-100 mg QD depending on disease. Metabolized in the liver to prednisolone. t1/2 ~ 18-36 hr
Adverse effects and counterindications of prednisone
CNS: headache, insomnia, vertigo, depression, anxiety, euphoria, personality changes, psychosis
GI: NVD, anorexia, gastritis
Cataracts
Opportunistic infections
Cushing’s syndrome. High doses and long-term therapy can suppress hypothalamic-pituitary-adrenal system; avoid abrupt DC of prolonged therapy. Preexisting bacterial, viral, fungal infections.Patients receiving corticosteroids chronically should be periodically assessed for cataracts
Description and mechanism of action of cyclosporine.
Immunosuppressive cyclic peptide produced by the fungus Beauveria nivea. Immunosuppressive effect was discovered in 1972, approved by FDA in 1983.Used to prevent organ rejection after transplant; TX for rheumatoid arthritis, psoriasis, inflammatory bowel disease.
Calcineurin inhibitor (CNI); binds to cyclophilin, complex binds to calcineurin and inhibits phosphatase activity of calcineurin; this prevents the dephosphorylation and translocation of a transcription factor (NF-AT) that stimulates cytokine gene expression. Result is inhibition of T cell activation and decreased release of IL-2, IL-3, IL-4, TNF-a, IFN-g
Pharmacokinetics of cyclosporine
Given PO or IV for immunosupression at 2.5-15 mg/kg QD; narrow therapeutic window. Opthalmic formulation 0.05% or 0.1% (Restasis®) is used to increase tear production that has been suppressed by inflammation, usually 1 gtt BID. Metabolized by CYP3A4 (→ drug interactions!), metabolites mostly excreted in bile
Adverse effects and counterindication of cyclosporine.
Nephrotoxicity (20-38%); CNIs induce interstitial fibrosis and vasoconstriction of afferent arterioles, leading to tubular necrosis
CV: hypertension (8-28%)
Hirsutism (10-21%) occurs in both ♂ and ♀ receiving systemic cyclosporine
Gingival hyperplasia (4-16%)
CNS: tremor (10-12%)
Opthalmic application may causes burning (17%)
Hyperglycemia (
Description of Tacrolimus
Immunosuppressive derived from the fungus Streptomyces tsukubaensis. Used to prevent organ rejection after transplant; psoriasis, atopic dermatitis.
Mechanism of action of tacrolimus
Calcineurin inhibitor (CNI); forms complex with FK binding protein, complex binds to calcineurin and inhibits phosphatase activity of calcineurin; this prevents the dephosphorylation and translocation of a transcription factor (NF-AT) that stimulates cytokine gene expression; 50-100X more potent than cyclosporine. Result is inhibition of T cell activation and decreased release of IL-2, IL-3, IL-4, TNF-a, IFN-g.
Pharmacokinetics of tacrolimus
Given IV or PO; PO absorption is highly variable, necessitating individualized regimens
Extensively metabolized by CYP3A4 (→ drug interactions!), metabolites excreted in bile
Concentrated in the pancreas and may inhibit pancreatic insulin secretion
Adverse effects and counterindications of tacrolimus
Nephrotoxicity (40-52%); CNI induce interstitial fibrosis and vasoconstriction of afferent arterioles, leading to tubular necrosis
CV: hypertension (38-50%)
CNS: tremor (48-56%), insomnia (32-64%), headache (37-64%)
GI: NVD (32-59%), elevated LFTs
Hyperglycemia (33-47%)
Diabetes. Therapeutic drug monitoring, target blood concentration is 5-20 ng/mL. Hepatic disease, renal disease, hypertension.
Description of Sirolimus
Macrocyclic lactone produced by Streptomyces hygroscopicus. Used to prevent rejection after renal transplant, not recommended for liver or lung transplants.
Mechanism of action of sirolimus
Binds to FK binding protein, complex then binds to and inhibits mTOR, a key kinase involved in upstream regulation of protein synthesis, cell growth, proliferation; inhibits progression from G1 to S phase of the cell cycle
Cytostatic: T cells still produce IL-2 but fail to proliferate
Pharmacokinetics of sirolimus
Supplied as a solution or tablets for PO administration, commonly 2-5 mg QD. Cypher® is a sirolimus-eluting stent used to inhibit restenosis after stenting to treat coronary artery occlusion; 80% of sirolimus is released in 30 days and the rest in 90 days. CYP3A4 substrate (→ drug interactions!), metabolites excreted in bile. Long, ca. 60 hr half-life
Adverse effects and precautions for sirolimus
PULM: dyspnea (22-30%), pharyngitis (16-21%)
HEME: myelosuppression (13-37%)
GI: NVD (19-42%), hepatotoxicity, elevated LFTs
MET: hyperlipidemia (35-57%), hypertriglyceridemia, electrolyte imbalances (11-23%), edema (54-64%)
Nephrotoxicity; may potentiate CNI-induced nephrotoxicity
Therapeutic drug monitoring, target concentration is 12-24 ng/mL
Description of azathioprine
Historically, first drug to be used for immunosuppression after transplantation
Cytotoxic antimetabolite-class agent; prodrug of 6-mercaptopurine (6-MP)
Used to prevent rejection of kidney transplants and to reduce symptoms of rheumatoid arthritis and Crohn’s disease; 6-MP itself is used as an antileukemia agent
Mechanism of action of azathioprine
Azathioprine → 6-MP → 6-thioguanine → 6-thioguanine nucleotides, which are incorporated into DNA and RNA → impaired function
6-MP and 6-thioguanine also interfere with several enzymes in the de novo purine nucleotide biosynthetic pathway, resulting in depletion of purine nucleotides, decreased ATP and GTP, decreased glycoproteins, etc
Pharmacokinetics of azathioprine
Administered as PO or IV, good oral absorption; usual maintenance dose is 1-3 mg/kg QD
6-MP is inactivated by oxidation (by xanthine oxidase) and methylation (by thiopurine S-methyltransferase); excretion is mostly renal
Adverse effects and precautions of azathioprine
HEM: myelosuppression (up to 50%), with potentially severe leukopenia
GI: NVD (12%), abdominal pain, elevated LFTs
Rashes
Thiopurine methyltransferase deficiency (ca. 10%) → enhanced toxicity
TX with allopurinol → enhanced toxicity
Pregnancy Risk Category D
Description of Muromonab-CD3
Murine monoclonal antibody directed against CD3 protein on surface of T cells
First monoclonal antibody to be FDA-approved (1985)
Used to block acute rejection of heart, liver, kidney transplants and to deplete T cells from donor bone marrow prior to transplantation
Mechanism of action of muromonab-CD3
Binds to T cell receptor-associated CD3 complex, causes initial activation and cytokine release, followed by blockade, apoptosis, and depletion of T cells
Pharmacokinetics of muromonab-CD3
Supplied as 1 mg/mL solution for IV bolus administration, usual dose is 5 mg QD for 10-14 days
T cells begin to disappear from blood within minutes and reappear ca. 1 week after therapy is halted
Adverse effects and precautions for muromonab-CD3
Triggers cytokine release syndrome: fever (73%), chills (59%), headache, tremor, dyspnea (21%), chest pain (14%), NVD (12%); syndrome subsides after first day and can be minimized by pretreatment with glucocorticoids, acetaminophen, or diphenhydramine
Seizures (1-5%)
Rare, but potentially fatal, anaphylaxis
Allergy to mouse proteins
CV: heart failure, hypertension, hypotension
Epilepsy
Description of Basiliximab
“Nondepleting” immunosuppressive agent. Anti-CD25 antibody; recombinant human-mouse IgG vs. IL-2 receptor-CD25 complex. Used for prophylaxis of acute rejection following kidney transplant, combined with cyclosporine and a glucocorticoid.
Mechanism of action of Basiliximab
IL-2 receptor antagonist; binds with high affinity (KD ca. 0.1 nM) to CD25, the IL-2 receptor a chain on activated T cells, preventing activation by IL-2
CD25 is only expressed on activated T cells, so basiliximab is does not cause widespread depletion of T cells
Pharmacokinetics of basiliximab
Supplied as a lyophylized powder that is reconstituted for IV administration
20 mg is given IV as a bolus injection or as an infusion over 20-30 min
First 20 mg dose is given 2 hr prior to surgery
Second 20 mg dose is given 4 days after transplantation
Elimination half-life is ca. 7 days; normal T cell numbers return in 7-14 days
Adverse effects and precautions for basiliximab
Incidence and severity much lower than muromonab-CD3 GI (10%): NVD, pain MET: electrolyte imbalances (3-10%) CV (3-10%): hypertension, arrhythmias Rare, potentially fatal anaphylaxis
Pediatric patients