Drugs with dual uses

Beta-Blockers (e.g., Propranolol, Metoprolol)
- Common: Hypertension, Angina (↓HR, contractility, renin).
- Other: Essential Tremor (peripheral β2 antagonism), Migraine Prophylaxis, Hyperthyroidism symptoms (block sympathetic effects), Performance Anxiety.
- Pearl: Can mask hypoglycemia, exacerbate asthma (non-selective).
Aspirin
- Common: Pain, Fever, Inflammation (COX-1 & COX-2 inhibition).
- Other: Antiplatelet for MI/Stroke prevention (irreversible COX-1 inhibition in platelets → ↓TXA2).
- Pearl: Reye's syndrome in children with viral illness; GI ulcers/bleeding.
Spironolactone
- Common: Heart Failure, Hypertension (aldosterone antagonist → K $^{+}$ sparing diuretic).
- Other: PCOS (hirsutism/acne - anti-androgenic effects).
- Pearl: Hyperkalemia; gynecomastia.
Metformin
- Common: Type 2 Diabetes (↓hepatic gluconeogenesis, ↑insulin sensitivity).
- Other: PCOS (improves insulin sensitivity → ↓androgens, may restore ovulation).
- Pearl: Lactic acidosis risk (esp. renal impairment); GI upset; B12 deficiency.
Gabapentin/Pregabalin
- Common: Seizures (adjunct - bind α2δ−1 subunit of Ca $^{2 +}$ channels → ↓excitoary neurotransmitter release).
- Other: Neuropathic Pain (same mechanism in pain pathways).
- Pearl: Sedation, dizziness; dose adjust in renal impairment.
SSRIs (e.g., Fluoxetine, Paroxetine)
- Common: Depression, Anxiety (↑serotonin in synaptic cleft).
- Other: Premature Ejaculation (serotonergic delay of ejaculation); Bulimia (Fluoxetine).
- Pearl: Sexual dysfunction; Serotonin Syndrome risk.
Minoxidil
- Common: Severe Hypertension (oral - direct arterial vasodilator via K $^{+}$ channel opening).
- Other: Hair Loss (topical/low-dose oral - vasodilation, direct follicle stimulation).
- Pearl: Oral: reflex tachycardia, fluid retention, hypertrichosis.
Sildenafil (PDE-5 Inhibitors)
- Common: Erectile Dysfunction (↑cGMP → smooth muscle relaxation in corpus cavernosum).
- Other: Pulmonary Arterial Hypertension (↑cGMP → pulmonary vasodilation).
- Pearl: Contraindicated with nitrates (severe hypotension); visual disturbances.
Colchicine
- Common: Acute Gout (inhibits microtubule polymerization → ↓neutrophil activity).
- Other: Pericarditis (anti-inflammatory via similar mechanism).
- Pearl: GI distress (diarrhea common); narrow therapeutic index.
Methotrexate
- Common: Cancer, Psoriasis (high dose - inhibits dihydrofolate reductase → ↓DNA/RNA synthesis).
- Other: Rheumatoid Arthritis (low dose DMARD - complex immunomodulation, ↑adenosine).
- Pearl: Myelosuppression, hepatotoxicity, mucositis, teratogenic. Leucovorin rescue (high dose).
Lithium
- Common: Bipolar Disorder (mood stabilizer - unclear, affects 2nd messengers/GSK-3).
- Other: Cluster Headache Prophylaxis; can induce Nephrogenic Diabetes Insipidus (ADH antagonism - used therapeutically in some SIADH).
- Pearl: Narrow therapeutic index; nephrotoxicity, hypothyroidism, teratogenic (Ebstein's).
N-Acetylcysteine (NAC)
- Common: Acetaminophen Overdose (replenishes glutathione).
- Other: Mucolytic (breaks disulfide bonds in mucus).
- Pearl: Acetaminophen OD: most effective if given early; IV can cause anaphylactoid reaction.
TCAs (e.g., Amitriptyline, Nortriptyline, Imipramine)
- Common: Depression (block norepinephrine and serotonin reuptake).
- Other: Neuropathic Pain (e.g., diabetic neuropathy, postherpetic neuralgia), Migraine Prophylaxis, Chronic Pain Syndromes (e.g., Fibromyalgia), OCD (Clomipramine has strong serotonergic effects), Enuresis (Imipramine - anticholinergic bladder effects).
- Pearl: Significant anticholinergic, antihistamine (sedation, weight gain), and alpha-adrenergic blockade (orthostatic hypotension) side effects; Cardiotoxicity (arrhythmias, QTc prolongation) and lethality in overdose; Narrow therapeutic index.