Pharmacology Essentials: Drug Forms, Actions, and Therapeutic Classes

Pharmacology Fundamentals

Medical Prescription Components and Units

A medical prescription includes the date, patient identification (such as name, age, and weight if relevant), the Rx symbol (meaning "take"), the inscription (drug name, strength, dosage form, and quantity), the subscription (instructions to the pharmacist), the signatura or "Sig." (directions for the patient including route, frequency, and duration), the prescriber's information (name, signature, license number), and refill instructions. Units of measurement include micrograms (µg), milligrams (mg), grams (g), milliliters (mL), liters (L), concentrations such as percentage (%) and mg/mL, international units (IU), and sometimes weight per kilogram of body weight. Obsolete units such as grains and minims may still appear in historical contexts.

Drug Origins and Sources

The origin of drugs can be natural, semi-synthetic, synthetic, or biotechnological. Natural sources include plants (yielding substances like alkaloids and glycosides), animals (providing hormones and enzymes), and minerals (offering salts and elements). Semi-synthetic drugs are derived from natural compounds that are chemically modified. Synthetic drugs are created entirely through chemical processes. Biotechnological drugs are produced using recombinant DNA technology, such as monoclonal antibodies and hormone analogs.

Drug Dosage Form Classifications

Drug dosage forms are classified into solid, liquid, semisolid, and gaseous forms. Solid forms include powders, tablets, and capsules. Liquid forms include solutions, suspensions, and emulsions. Semisolid forms include ointments, creams, and gels. Gaseous forms include aerosols and inhalers. Galenic preparations, also called phytomedicinals, are plant-based medicinal forms named after the physician Galen and include decoctions, infusions, tinctures, and extracts.

Solid Dosage Forms: Powders and Tablets

Solid dosage forms include powders and tablets. Powders are finely divided dry drug forms used either internally or externally. Tablets are compressed solid forms that may be uncoated, film-coated, sugar-coated, chewable, effervescent, or designed for sustained or extended release.

Other Solid Dosage Forms

Other solid dosage forms include capsules, pills, troches, granules, and suppositories. Capsules are gelatin shells containing powdered or liquid drugs. Pills are small round solid forms, less commonly used today. Troches, or lozenges, are designed to dissolve slowly in the mouth for local effect. Granules are larger particles than powders and often require reconstitution. Suppositories are molded solid forms that melt at body temperature and are used rectally, vaginally, or urethrally.

Liquid Dosage Forms

Liquid dosage forms include solutions, emulsions, and suspensions. Solutions are homogeneous mixtures where the drug is completely dissolved. Emulsions are mixtures of two immiscible liquids, such as oil and water, stabilized by emulsifying agents. Suspensions consist of insoluble particles dispersed in a liquid base and must be shaken before use.

Additional Liquid Forms

Additional liquid forms include mixtures, mucilages, drops, and sterile injectables. Mixtures are liquid preparations containing more than one dissolved or suspended ingredient. Mucilages are thick, sticky plant-based preparations. Drops are concentrated liquid forms used for nasal, ophthalmic, or otic administration. Sterile injectables are parenteral preparations that must be free from contaminants and pyrogens and can be administered via intravenous, intramuscular, subcutaneous, or intradermal routes.

Semisolid Dosage Forms

Semisolid dosage forms include ointments, liniments, and gels. Ointments are greasy preparations used primarily for dry, scaly lesions. Liniments are liquid or semisolid preparations applied with rubbing, often containing alcohol or oil. Gels are water-based semisolid systems that are clear, non-greasy, and provide good patient acceptability and absorption.

Further Semisolid Dosage Forms

Additional semisolid dosage forms include plasters and plaques. Plasters are adhesive semisolid or solid masses spread on a backing material and applied to the skin to provide localized and prolonged drug delivery. Plaques are flat, disc-like solid dosage forms used topically, sometimes in dental or dermatologic treatments.

Aerosol Dosage Forms

Aerosols are pressurized dosage forms that deliver drugs in the form of a fine mist or spray. They are primarily used in respiratory therapy for conditions such as asthma and COPD. The drug is dispensed via metered-dose inhalers or nebulizers, and the particle size must be appropriate (typically 1–5 microns) to reach the lower respiratory tract effectively.

Key Drug Classes and Therapeutic Actions

Endocrine and Hormonal Agents

Drugs Acting on the Uterus

• Tocolytics (inhibit uterine contractions):
  • First-line: Indomethacin (NSAID, 24–32 GW), Nifedipine (calcium channel blocker, 32–34 GW)
  • Second-line: Terbutaline (β2-agonist), Magnesium sulfate
  • Used for: Delaying preterm labor up to 48h for corticosteroid administration
  • Contraindicated in: Myasthenia gravis, chorioamnionitis, fetal distress, severe preeclampsia
• Labor Inducers:
  • Prostaglandins: Misoprostol, Dinoprostone (intravaginal)
  • Oxytocin: IV; promotes uterine contractions and cervical dilation

Hypothalamic, Pituitary, Thyroid, and Antithyroid Drugs

• Hypothalamic hormones:
  • GnRH analogs: Buserelin, Goserelin – treat infertility
  • Somatostatin analogs: Octreotide, Lanreotide – treat acromegaly
  • GHRH analog: Tesamorelin – for HIV lipodystrophy
  • Dopamine agonists: Bromocriptine, Cabergoline – reduce prolactin
• Anterior pituitary hormones:
  • FSH analog: Urofollitropin – stimulates gametogenesis
  • ACTH analog: Tetracosactide – tests adrenal function
  • GH analog: Somatotropin – treats GH deficiency
  • Prolactin inhibitors: Bromocriptine, Cabergoline
• Posterior pituitary hormones:
  • Oxytocin: Induces labor
  • ADH/Vasopressin: Regulates water retention and BP
• Thyroid hormones:
  • T4 (levothyroxine), T3 (liothyronine) – hormone replacement for hypothyroidism
• Antithyroid drugs:
  • Thionamides: Methimazole, Propylthiouracil – inhibit thyroid peroxidase (PTU also blocks T4→T3)
  • Iodides: Lugol's iodine, SSKI – inhibit hormone release pre-surgery or in thyroid storm

Parathyroid Hormones, Vitamin D, and Bone Drugs

• Parathyroid hormone (PTH): Increases serum calcium via bone resorption and renal reabsorption
• Vitamin D (Calcitriol): Enhances calcium/phosphate absorption from gut; made in skin/liver/kidney
• Drugs for osteoporosis and bone health:
  • Bisphosphonates: Alendronate, Risedronate – inhibit osteoclasts
  • Calcitonin: Decreases bone resorption; used in vertebral fractures
  • Denosumab: Monoclonal antibody that inhibits osteoclast function
  • Teriparatide: PTH analog that stimulates bone formation

Pancreatic Hormones and Antidiabetic Drugs

• Insulin types:
  • Rapid-acting: Lispro, Aspart, Glulisine
  • Short-acting: Regular insulin
  • Intermediate-acting: NPH
  • Long-acting: Glargine, Detemir, Degludec
  • Mixed insulin: Premixed combinations for basal/bolus regimens
• Insulinotropic drugs:
  • Sulfonylureas: Glipizide, Glyburide – ↑ insulin (risk of hypoglycemia)
  • Meglitinides: Repaglinide – short-acting secretagogue
  • GLP-1 agonists: Exenatide, Liraglutide – ↑ insulin, ↓ glucagon, ↓ weight
  • DPP-4 inhibitors: Sitagliptin, Saxagliptin – ↑ endogenous GLP-1
• Non-insulinotropic drugs:
  • Biguanides: Metformin – ↓ hepatic glucose, ↑ sensitivity
  • SGLT-2 inhibitors: Canagliflozin, Dapagliflozin – ↑ renal glucose excretion
  • Thiazolidinediones: Pioglitazone – ↑ insulin sensitivity via PPARγ
  • α-glucosidase inhibitors: Acarbose – ↓ carb absorption
  • Amylin analog: Pramlintide – ↓ glucagon, delays gastric emptying

Glucocorticoids and Mineralocorticoids

• Systemic glucocorticoids:
  • Short-acting: Hydrocortisone, Cortisone
  • Intermediate-acting: Prednisone, Prednisolone, Methylprednisolone
  • Long-acting: Dexamethasone, Betamethasone
• Mineralocorticoid:
  • Fludrocortisone: For adrenal insufficiency; mimics aldosterone
• Key actions: Anti-inflammatory, immunosuppressive, metabolic, anti-proliferative
• Adverse effects: Hyperglycemia, osteoporosis, Cushingoid features, adrenal suppression

Male Sex Hormones and Anabolic Steroids

• Testosterone, Methyltestosterone: Hormone replacement
• Anabolic steroids: Increase muscle mass; risk of liver toxicity, infertility, aggression

Female Sex Hormones and Contraceptives

• Estrogens: Ethinyl estradiol, Mestranol – used in HRT, contraception
  • Risks: Thromboembolism, cancer (e.g., endometrial, if unopposed)
• Progestins: Prevent ovulation and implantation, alter cervical mucus
  • Used in: OCPs, hormone therapy, endometriosis
• SERMs:
  • Tamoxifen: Estrogen antagonist in breast, agonist in uterus and bone
  • Raloxifene: Antagonist in breast and uterus, agonist in bone
  • Clomiphene: Increases FSH/LH for ovulation induction
• Contraceptives:
  • Combined OCPs (estrogen + progestin): Inhibit ovulation and implantation
  • Adverse effects: VTE, hypertension, nausea
  • CI: Smokers >35 y/o, history of thromboembolism or hormone-sensitive cancer

Gastrointestinal System Drugs

Antiulcer Drugs

• Acid Suppressors:
  • PPIs (proton pump inhibitors): Omeprazole, Pantoprazole — inhibit H⁺/K⁺ ATPase
  • H2-receptor blockers: (not detailed in doc but typically ranitidine, famotidine)
• Cytoprotective Agents:
  • Sucralfate: Forms protective barrier; avoid with PPIs/H2-blockers
  • Misoprostol: PGE1 analog, especially in NSAID-induced ulcers
• H. pylori Eradication:
  • Triple therapy: PPI + Clarithromycin + Amoxicillin/Metronidazole
  • Quadruple therapy: PPI + Bismuth + Tetracycline + Metronidazole

Laxatives and Antidiarrheals

• Laxatives:
  • Osmotic: PEG, Lactulose, Sorbitol — draw water into intestine
  • Stimulant: Senna, Bisacodyl — stimulate secretion & motility
  • Emollient (stool softeners): Docusate
  • Bulk-forming: Psyllium, Methylcellulose — increase stool bulk via water absorption
• Antidiarrheals:
  • Symptomatic treatment: Oral rehydration (mainstay)
  • Agents (if needed): Loperamide (avoid with bloody stool/fever)
  • Antibiotics: Generally not used unless specific pathogen confirmed

Antiemetics and Spasmolytics

• Antiemetics:
  • Dopamine antagonists: Metoclopramide (contraindicated in Parkinson’s)
  • Serotonin antagonists: Ondansetron (caution in liver disease, QT prolongation)
  • Antihistamines/Anticholinergics: Used in motion sickness, vertigo
• Spasmolytic agents (smooth muscle relaxants):
  • Drotaverine (No-Spa), Papaverine, Atropine-like agents: Reduce GI or uterine smooth muscle spasms

Respiratory System Drugs

Antiasthmatic Drugs

• Acute Management:
  • SABA (short-acting β2 agonists): Albuterol, Terbutaline
  • SAMA (short-acting muscarinic antagonist): Ipratropium
  • Systemic corticosteroids: Prednisone, Methylprednisolone
• Long-Term Control:
  • ICS (inhaled corticosteroids): Budesonide, Fluticasone, Mometasone
  • LABA: Salmeterol, Formoterol
  • LAMA: Tiotropium
  • LTRA (leukotriene receptor antagonists): Montelukast, Zafirlukast
• Others:
  • Monoclonal antibodies: Omalizumab (anti-IgE), Mepolizumab (anti-IL-5)
  • Methylxanthines: Theophylline (rarely used)
  • Mast cell stabilizers: Cromolyn sodium, Nedocromil
  • Leukotriene synthesis inhibitor: Zileuton

Antitussive Drugs and Expectorants

• Antitussives (cough suppressants):
  • Centrally acting: Dextromethorphan, Codeine
  • Peripherally acting: Benzonatate
• Expectorants (mucus clearance):
  • Guaifenesin: Increases secretion hydration
  • Mucolytics: N-acetylcysteine (breaks mucus bonds, also used in acetaminophen poisoning)
• Indications depend on cough type:
  • Non-productive: Antitussives
  • Productive: Expectorants, mucolytics, chest physiotherapy

Cardiovascular and Metabolic Agents

Lipid-Lowering Drugs

• Statins (HMG-CoA reductase inhibitors):
  • Drugs: Atorvastatin, Simvastatin, Rosuvastatin
  • Mechanism: Inhibit cholesterol synthesis → ↑ LDL receptor expression → ↓ LDL
  • Effects: ↓ LDL (most effective), ↓ triglycerides, mild ↑ HDL
  • Side effects: Myopathy, ↑ liver enzymes, rhabdomyolysis (esp. with fibrates), contraindicated in pregnancy
• Fibrates:
  • Drugs: Gemfibrozil, Fenofibrate
  • Mechanism: Activate PPAR-α → ↑ LPL activity → ↓ triglycerides
  • Effects: ↓ triglycerides (most effective), mild ↓ LDL, ↑ HDL
  • Side effects: Gallstones, myopathy (↑ risk with statins), GI upset
• Bile Acid Sequestrants:
  • Drugs: Cholestyramine, Colestipol, Colesevelam
  • Mechanism: Bind bile acids in intestine → ↓ cholesterol reabsorption
  • Effects: ↓ LDL, slight ↑ HDL, may ↑ triglycerides
  • Side effects: GI issues, impaired absorption of fat-soluble vitamins and some drugs
• Niacin (Vitamin B3):
  • Mechanism: ↓ lipolysis in adipose tissue, ↓ hepatic VLDL synthesis
  • Effects: ↑ HDL (most effective), ↓ LDL and triglycerides
  • Side effects: Flushing (↓ with aspirin), hyperglycemia, hyperuricemia, hepatotoxicity
• Cholesterol Absorption Inhibitor:
  • Drug: Ezetimibe
  • Mechanism: Inhibits NPC1L1 transporter in intestine → ↓ cholesterol absorption
  • Effects: ↓ LDL, minimal effect on HDL/triglycerides
  • Side effects: Rare; mild GI effects
• PCSK9 Inhibitors:
  • Drugs: Alirocumab, Evolocumab
  • Mechanism: Monoclonal antibodies inhibit PCSK9 → ↑ LDL receptor recycling
  • Effects: Profound ↓ LDL
  • Side effects: Injection site reactions, neurocognitive effects (rare)

Hematopoietic System Drugs

Drugs Affecting the Hemopoietic System

• Iron preparations:
  • Oral: Ferrous sulfate, ferrous gluconate
  • Parenteral: Iron dextran, iron sucrose, ferric carboxymaltose
  • Side effects: GI irritation (oral), anaphylaxis (parenteral)
• Vitamin B12 (cyanocobalamin, hydroxocobalamin):
  • Route: Oral (mild deficiency), IM (malabsorption)
  • Use: Pernicious anemia, B12 deficiency
  • Deficiency leads to: Megaloblastic anemia, neurologic symptoms
• Folic acid:
  • Use: Prevention and treatment of megaloblastic anemia, especially in pregnancy or alcoholism
  • Note: Does not reverse neurologic deficits of B12 deficiency
• Erythropoiesis-stimulating agents (ESAs):
  • Drugs: Epoetin alfa, Darbepoetin
  • Use: Anemia in chronic kidney disease, cancer therapy
  • Side effects: Hypertension, thromboembolic events
• Myeloid growth factors:
  • Drugs: Filgrastim (G-CSF), Sargramostim (GM-CSF)
  • Use: Neutropenia, bone marrow recovery
  • Side effects: Bone pain, fever
• Thrombopoietic agents:
  • Drugs: Romiplostim (TPO analog), Eltrombopag (TPO receptor agonist)
  • Use: Immune thrombocytopenia (ITP), aplastic anemia

Neurological and Psychiatric Drugs

Antiparkinson Drugs

• Dopaminergic therapy:
  • Levodopa (L-DOPA): Precursor to dopamine; most effective
  • Carbidopa: DOPA decarboxylase inhibitor; prevents peripheral conversion of L-DOPA, ↑ CNS availability, ↓ side effects
  • Side effects: Dyskinesia, on-off phenomena, hallucinations
• Dopamine agonists:
  • Ergot-derived: Bromocriptine
  • Non-ergot: Pramipexole, Ropinirole, Rotigotine
  • Use: Early disease or adjunct to L-DOPA
  • Side effects: Impulse control disorders, hallucinations
• MAO-B inhibitors:
  • Selegiline, Rasagiline: ↓ dopamine breakdown in CNS
  • Adjuvant therapy to prolong L-DOPA action
• COMT inhibitors:
  • Entacapone, Tolcapone: Inhibit L-DOPA metabolism; enhance duration
  • Tolcapone: Risk of hepatotoxicity
• Anticholinergics:
  • Benztropine, Trihexyphenidyl: ↓ cholinergic activity; useful for tremor and rigidity
  • Side effects: Dry mouth, confusion, constipation
• Other:
  • Amantadine: Increases dopamine release, inhibits reuptake; used in early stages
  • Side effects: Livedo reticularis, edema, hallucinations

Antipsychotic Drugs

• Typical antipsychotics (First-generation):
  • High-potency: Haloperidol, Fluphenazine – strong D2 antagonists
  • Low-potency: Chlorpromazine, Thioridazine – also block H1, M, α1 receptors
  • Effects: Treat positive symptoms of schizophrenia
  • Side effects: Extrapyramidal symptoms (EPS), hyperprolactinemia, QT prolongation, sedation, anticholinergic effects, NMS (neuroleptic malignant syndrome)
• Atypical antipsychotics (Second-generation):
  • Drugs: Clozapine, Olanzapine, Risperidone, Quetiapine, Aripiprazole, Ziprasidone
  • Mechanism: D2 and 5-HT2A antagonism
  • Advantages: ↓ EPS, better effect on negative symptoms
  • Clozapine: Best efficacy, but risk of agranulocytosis, seizures, myocarditis – requires regular CBC
  • Risperidone: ↑ prolactin
  • Olanzapine, Clozapine: Weight gain, metabolic syndrome

Antidepressants and Antimaniac Drugs

• SSRIs (Selective Serotonin Reuptake Inhibitors):
  • Drugs: Fluoxetine, Sertraline, Citalopram, Escitalopram, Paroxetine
  • Use: First-line for depression, anxiety
  • Side effects: GI upset, sexual dysfunction, insomnia, serotonin syndrome
• SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors):
  • Drugs: Venlafaxine, Duloxetine
  • Use: Depression, neuropathic pain, GAD
  • Side effects: Hypertension, insomnia
• Tricyclic antidepressants (TCAs):
  • Drugs: Amitriptyline, Nortriptyline, Imipramine, Clomipramine
  • Mechanism: Block 5-HT and NE reuptake
  • Side effects: Anticholinergic (dry mouth, urinary retention), sedation, cardiotoxicity (arrhythmia via Na⁺ channel blockade), coma
• MAO inhibitors:
  • Drugs: Phenelzine, Tranylcypromine, Selegiline
  • Use: Atypical depression
  • Interaction: Tyramine-rich foods → hypertensive crisis
  • Serotonin syndrome risk when combined with SSRIs
• Atypical antidepressants:
  • Bupropion: ↑ NE and dopamine; no sexual side effects; risk of seizures
  • Mirtazapine: α2 antagonist; causes weight gain, sedation
  • Trazodone: 5-HT modulator; causes sedation, priapism
• Antimaniac drugs (Mood stabilizers):
  • Lithium: Inhibits inositol signaling; used in bipolar disorder
  • Side effects: Tremor, hypothyroidism, nephrogenic diabetes insipidus, teratogenicity (Ebstein anomaly)
  • Narrow therapeutic index: Monitor levels
  • Others: Valproate, Carbamazepine, Lamotrigine (also antiepileptic drugs)

Histamine and Serotonin Modulators

Histamine and Drugs Acting on Histamine Transmission

• Histamine Functions:
  • Released from mast cells, basophils
  • Causes vasodilation, ↑ capillary permeability, bronchoconstriction, gastric acid secretion
  • Acts via H1 (inflammatory/allergic response) and H2 (gastric secretion) receptors
• H1 Antihistamines:
  • 1st Generation (sedative, cross BBB):
    • Drugs: Diphenhydramine, Meclizine, Doxylamine, Promethazine, Clemastine, Chlorpheniramine, Dimetindene
    • Effects: Sedation, antiemetic, anticholinergic
    • Uses: Allergy, motion sickness, insomnia, nausea
    • Side effects: Sedation, dry mouth, urinary retention, hypotension
  • 2nd Generation (non-sedative):
    • Drugs: Loratadine, Desloratadine, Cetirizine, Fexofenadine
    • Uses: Allergic rhinitis, urticaria
    • Side effects: Minimal CNS effects, no sedation
• H2 Antihistamines:
  • Drugs: Ranitidine, Cimetidine, Famotidine, Nizatidine
  • Mechanism: Block H2 receptors in gastric parietal cells → ↓ acid secretion
  • Uses: Peptic ulcer, GERD
  • Side effects (esp. Cimetidine): Gynecomastia, impotence, drug interactions (CYP inhibition), CNS effects
• Other Agents:
  • Mast cell stabilizers: Cromolyn sodium, Ketotifen – inhibit histamine release
  • Combined products and topical H1 blockers are also available (e.g., for nasal or ocular use)

Serotonin and Drugs Acting on Serotonin Transmission

• Serotonin (5-HT):
  • Synthesized from L-tryptophan
  • Found in GIT, platelets, CNS (raphe nuclei)
  • Functions: GI motility, vasoconstriction, mood regulation, platelet aggregation, emesis control
• Serotonin Agonists:
  • 5-HT1A agonist (anxiolytic): Buspirone
  • 5-HT1B/1D agonists (anti-migraine): Sumatriptan, Naratriptan, Almotriptan
  • 5-HT2A agonist (antihypertensive): Ketanserin
  • 5-HT2C agonists (appetite suppressant): Fenfluramine, Lorcaserin
  • Serotonin reuptake inhibitors (SSRIs – antidepressants): Fluoxetine, Paroxetine, Sertraline
• Serotonin Antagonists:
  • 5-HT2 antagonists (migraine prophylaxis): Pizotifen
  • 5-HT2 + H1 antagonists: Cyproheptadine, Azatadine
  • 5-HT3 antagonists (antiemetics): Ondansetron, Granisetron, Tropisetron

Immunology and Oncology Drugs

Drugs Used in Cancer Chemotherapy

• Main drug classes:
  • Alkylating agents: Cyclophosphamide, Ifosfamide – cross-link DNA, impair replication
  • Antimetabolites: Methotrexate (folate analog), 5-FU (pyrimidine analog), 6-MP (purine analog) – inhibit DNA synthesis
  • Microtubule inhibitors: Vincristine, Paclitaxel – block mitosis (M phase)
  • Topoisomerase inhibitors: Etoposide (Topo II), Irinotecan (Topo I) – cause DNA breaks
  • Antitumor antibiotics: Doxorubicin, Bleomycin – bind DNA, generate free radicals
  • Hormonal agents: Tamoxifen, Letrozole (breast cancer); Flutamide, Leuprolide (prostate)
  • Monoclonal antibodies: Rituximab (CD20), Trastuzumab (HER2), Bevacizumab (VEGF)
  • Targeted agents: Imatinib (BCR-ABL), Erlotinib (EGFR)
  • Checkpoint inhibitors: Nivolumab (PD-1), Ipilimumab (CTLA-4)
• Common adverse effects: Myelosuppression, nausea, vomiting, mucositis, alopecia, immunosuppression

Immunomodulators

• Calcineurin inhibitors:
  • Cyclosporine: Binds cyclophilin → inhibits calcineurin → ↓ IL-2 → ↓ T-cell activation; used for transplant rejection, psoriasis, RA; nephrotoxicity, hirsutism, HTN, gingival hyperplasia
  • Tacrolimus: Binds FKBP → same pathway as cyclosporine; more potent, less hirsutism; nephrotoxicity, diabetes
  • Pimecrolimus (topical): Atopic dermatitis
• mTOR inhibitors:
  • Sirolimus (Rapamycin), Everolimus: Bind FKBP → inhibit mTOR → ↓ IL-2 response → ↓ T and B cells; used in renal transplant, drug-eluting stents; pancytopenia, hyperlipidemia, insulin resistance (no nephrotoxicity)
• Purine analog:
  • Azathioprine (6-MP precursor): ↓ lymphocyte proliferation; used for transplant, RA, Crohn's; myelosuppression, hepatotoxicity, pancreatitis (worse with allopurinol)
• IMPDH inhibitors:
  • Mycophenolate mofetil: Inhibits inosine monophosphate dehydrogenase → ↓ purine synthesis in lymphocytes; used for transplant, lupus nephritis; pancytopenia, infection (esp. CMV), GI upset, hyperglycemia
• Other cytostatics:
  • Methotrexate: Inhibits DHFR → ↓ nucleotide synthesis; used in RA, psoriasis, trophoblastic tumors; pancytopenia, hepatotoxicity, mucositis, pulmonary fibrosis
  • Cyclophosphamide: Alkylates DNA; used in autoimmune diseases (e.g., SLE); hemorrhagic cystitis, infertility, immunosuppression
• Biologic agents:
  • Include monoclonal antibodies and checkpoint inhibitors (e.g., anti-TNF, anti-CD20, anti-IL)
  • Side effects: rash, flu-like symptoms, anti-drug antibodies, infections, LFT abnormalities, cytopenias