RHS Antimycobacterials, Antimalarials, & Chemo Flashcards
Rifampin
Rifamycin. Part of RIPE (first-line anti-Tb drugs). Also part of DR Clof (for Leprosy)
Inhibitor of bacterial RNA polymerase
Resistance: point mutations in rpoB gene (gene for b subunit of RNA pol)
AE: Red body fluids, nephrotoxicity, rashes, hepatotoxicity
CYP inducer, Safe in pregnancy
Rifabutin
Rifamycin. Part of RIPE (first-line anti-Tb drugs).
Inhibitor of bacterial RNA polymerase
Resistance: point mutations in rpoB gene (gene for b subunit of RNA pol)
AE: Red body fluids, nephrotoxicity, rashes, hepatotoxicity
Not a CYP inducer so preferred into Rifampin in HIV patients.
Isoniazid
Part of RIPE (first-line anti-Tb drugs).
Mycolic Acid synthesis inhibitor
Resistance: deletion of Kat G- catalase peroxidase (high resistance), overexpression of inhA and KasA (low resistance)
AE: Neurotoxicity (treatable with vit B6), Lupus-like syndrome, Hemolysis in G6PD, Hepatotoxicity!!
CYP inhibitor. Safe in pregnancy. Metabolized by N-Acetyltransferase so higher dose needed in fast acetylator.
Pyrazinamide
Part of RIPE (first-line anti-Tb drugs).
MOA unclear. Is activated by hydrolysis by mycobacterial pyrazinamidase (pncA).
Resistance: Impaired uptake or mutations in pncA
AE: Non-gouty polyarthalgia, Hyperuricema (not given in gout), Hepatotoxicity, Myalgia, Porphyria, Photosensitivity.
Can be given in pregnancy but has risks.
Ethambutol
Part of RIPE (first-line anti-Tb drugs).
Inhibits arabinosyltransferases (emb) leading to decreased carbohydrate polymerization of bac cell wall.
Resistance: Mutations/Overexpression of emb.
AE: Visual disturbance, colorblindness, retinal damage. Not given in children too young to assess for colorblindness.
Safe in pregnancy.
Streptomycin
Part of SEAL (2nd line anti-Tb drugs)
Aminoglycoside: binds 30s subunit, inhibits bacterial ribosome.
AE: Ototoxicity, Nephrotoxicity, Unsafe in pregnancy.
Ethionamide
Part of SEAL (2nd line anti-Tb drugs)
Isoniazid-like. Inhibits mycolic acid synthesis.
AE: GI upset, neurotoxicity (alleviated by Vit B6)
Amikacin
Part of SEAL (2nd line anti-Tb drugs)
Aminoglycoside: binds 30s subunit, inhibits bacterial ribosome.
AE: Ototoxicity, Nephrotoxicity, Unsafe in pregnancy.
Is still effective in multidrug-resistant strains of TB
Levofloxacin
Part of SEAL (2nd line anti-Tb drugs)
Fluoroquinolone. Inhibits bacterial DNA gyrase
AE: Tendinopathy. Unsafe in pregnancy.
Dapsone
Part of DR Clof- treatment for Leprosy.
Inhibits folate synthesis via dihydropteroate synthetase inhibition.
AE: Hemolysis in G6PD. Methemoglobinema (Fe3 hemoglobin), Erythema nodosum leprosum.
Clofazimine
Part of DR Clof- treatment for Leprosy. Only given in Multi-bacillary leprosy.
Binds bacterial DNA, inhibits replication.
AE: Discoloration of skin and conjunctiva.
Methotrexate
Antimetabolite: Folate Analog
Inhibits dihydrofolate reductase (DHFR), decreasing synthesis of dTMP & purines. Effect potentiated by conversion to polyglutamates (MTX-PG) by folylpolyglutamate synthase (FPGS).
Kills cells in S phase.
Resistance via: Decreased influx, decreased FPGS activity, Altered or amplified DHFR.
AE: Stomatitis, mucositis, BM sup, thrombocytopenia, erythema, rash, alopecia, N/V. Nephrotoxic at high doses. Hepatotoxic. Pneumonitis. Neurotoxic if administered into CSF (spinal).
Leucovorin
Folate Analog
Decreases BM suppressive effect of Methotrexate.
Potentiates 5-FU.
6-Mercaptopurine
Antimetabolite: Purine Analog (Thiol analog of hypoxanthine)
Converted to 6-MPRP/TIMP by HGPRT. TIMP inhibits first step of denovo purine synthesis & blocks formation of AMP & GMP from IMP.
Resistance: HGPRT deficiency, increased metabolism of drug, increased dephosphorylation.
AE: N/V, diarrhea, BM sup, hepatotoxicity.
Special: Used in Acute Lymphatic Leukemia. Dose needs to be reduced in poor TMPT metabolizers. Dose needs to be reduced if given with allopurinol (allopurinol inhibits enzyme that metabolized 6-MP to inactive form).
6-Thioguanine
Antimetabolite: Purine Analog
Converted to TGMP by HGPRT. TGMP inhibits purine ring synthesis & phosphorylation of GMP to GDP.
AE: N/V, diarrhea, BM sup, hepatotoxicity.
Special: Used in Acute non-lymphocytic Leukemia. Dose needs to be reduced in poor TPMT metabolizers. No Allopurinol interactions.
5-Fluorouracil
Antimetabolite: Pyrimidine Analog
Converted to 5-FdUMP which inhibits formation of dTMP from dUMP. Causes thymine-less death. Also converted to 5-FUTP which is incorporated into RNA. Given IV due to GI toxicity.
Resistance: No conversion to 5-FdUMP, altered thimydilate synthase, increased catabolism of 5-FU.
AE: N/V, diarrhea, alopecia, GI ulceration, BM sup, anorexia. Dermatopathy: Hand-Foot syndrome.
Special: Used in colorectal cancer (with Leucovorin)
Cytarabine
Antimetabolite: Pyrimidine Analog
Converted to ara-CTP, incorporated into DNA, inhibits DNA polymerase. Not orally effective.
AE: N/V, diarrhea, Severe BM sup, hepatotoxicity, seizures or AMS.
Special: Used in acute non-lymphocytic leukemia.
Doxorubicin
Antitumor Antibiotic: Anthracycline
Topoisomerase II inhibition, DNA intercalation, iron-dependent generation of free radicals which break DNA strands, altering membrane ion transport & fluidity.
Resistance: P-glycoprotein increased efflux, glutathione peroxidase increase, mutation in topoisomerase 2.
AE: BM suppression, cardiotoxicity (can be alleviated with dexrazoxane).
Daunorubicin
Antitumor Antibiotic: Anthracycline
Topoisomerase II inhibition, DNA intercalation, iron-dependent generation of free radicals which break DNA strands, altering membrane ion transport & fluidity.
Resistance: P-glycoprotein increased efflux, glutathione peroxidase increase, mutation in topoisomerase 2.
AE: BM suppression, cardiotoxicity (can be alleviated with dexrazoxane).
Bleomycin
Antitumor Antibiotic.
Mixture of glycopeptides. Binds to DNA, generates free radicals which cause strand breakage.
Resistance in tissues with Bleomycin hydrolase.
AE: Very mild BM sup. Pulmonary toxicity!
Mechlorethamine
Alkylating Agent: Nitrogen Mustard
Cytotoxic by transfer of alkyl groups to DNA.
AE: N/V, severe BM sup, alopecia.
Special: Unstable & causes blisters (given IV only). Largely replaced by cyclophosphamide & other agents.
Cyclophosphamide
Alkylating Agent: Nitrogen Mustard
Cytotoxic by transfer of alkyl groups to DNA. Prodrug activated by CYP2B. Most widely used.
AE: N/V, BM sup, Hemorrhagic cystitis!!!, Alopecia, Sterility.
Special: Hemorrhagic cystitis caused by Acrolein metabolite. Prevented thru adequate fluid intake + Mesna.
Mesna
Sulfhydryl compound which neutralizes acrolein in the bladder.
Prevents Hemorrhagic Cystitis adverse effect of Cyclophosphamide & Ifosfamide.
Ifosfamide
Alkylating Agent: Nitrogen Mustard
Cytotoxic by transfer of alkyl groups to DNA. Analog of Cyclophosphamide. Prodrug activated by hydroxylation by CYP3A4.
AE: Greater BM sup, Neurotoxicity, Greater urinary tract toxicity. Only given with adequate hydration & mesna.
Melphalan
Alkylating Agent: Nitrogen Mustard
Cytotoxic by transfer of alkyl groups to DNA.
AE: BM sup
Carmustine
Alkylating Agent: Nitrosoureas
Cytotoxic by transfer of alkyl groups to DNA.
Very lipophilic, crosses blood-brain barrier, treats brain tumors.
Lomustine
Alkylating Agent: Nitrosoureas
Cytotoxic by transfer of alkyl groups to DNA.
Very lipophilic, crosses blood-brain barrier, treats brain tumors.