Midodrine

# Midodrine ## Overview - **Classification**: Alpha-1 adrenergic agonist (prodrug) - **Mechanism**: Midodrine is converted to desglymidodrine, an active metabolite. This stimulates alpha-1 adrenergic receptors on arterioles and venules, causing vasoconstriction and increasing blood pressure. ## Primary Indications 1. **Symptomatic Orthostatic Hypotension** - To increase standing blood pressure in patients whose life is considerably impaired by a reproducible symptomatic drop in blood pressure. ## Adult Dosing ### Standard Dosing **Symptomatic Orthostatic Hypotension** - **Dose**: Start with **2.5 mg** - **Frequency**: 2 to 3 times daily (TID) - **Route**: Oral - **Titration**: May increase weekly to **5 mg** TID, then to **10 mg** TID if needed. - **Maximum Dose**: **10 mg** per dose, **30 mg** daily. - **Special Considerations**: Administer during daytime hours, when patient is upright. Last dose should be at least **4 hours before bedtime** to minimize supine hypertension. ### Dose Adjustments - **Renal Impairment**: - CrCl 30-60 mL/min: Reduce dose by 25% to 50% (e.g., **2.5 mg** BID to TID). - CrCl <30 mL/min: Contraindicated due to risk of accumulation and adverse effects. - **Hepatic Impairment**: No specific dose adjustment guidelines; use with caution. - **Elderly Patients**: Start with lower doses (e.g., **2.5 mg** TID) and titrate slowly due to potential for decreased renal function and increased sensitivity. ## Pediatric Dosing *Note: Midodrine is generally not approved for pediatric use by the FDA; use is off-label and requires specialist consultation. Dosing is highly individualized.* ### Neonates (0-28 days) - **Dose**: Limited data. Consult a pediatric specialist. - **Frequency**: N/A - **Maximum**: N/A - **Special Notes**: Use with extreme caution, if at all. ### Infants (1-12 months) - **Dose**: Limited data. Typically starts at **0.05-0.1 mg/kg/dose**. - **Frequency**: 2-3 times daily (TID) - **Maximum**: Not clearly established for this age group; individualize based on response and adverse effects. - **Special Notes**: Monitor closely for hypertension, bradycardia. ### Children (1-12 years) - **Dose**: Initial **0.05-0.1 mg/kg/dose**. - **Frequency**: 2-3 times daily (TID). - **Titration**: May titrate up to **0.2 mg/kg/dose** based on response and tolerance. - **Maximum**: Typically up to **5 mg** per dose initially; maximum daily dose rarely exceeds **30 mg** (adult max). - **Special Notes**: Closely monitor blood pressure (supine and standing) and heart rate. ### Adolescents (13-18 years) - **Dose**: Approach adult dosing, starting with **2.5 mg** - **Frequency**: 2-3 times daily (TID). - **Maximum**: **10 mg** per dose, **30 mg** daily. - **Special Notes**: Initiate at the lowest effective dose and titrate cautiously. ## Safety Information ### Contraindications - **Absolute**: Severe organic heart disease, acute renal disease, urinary retention. - **Absolute**: Pheochromocytoma, thyrotoxicosis, persistent and excessive supine hypertension. - **Absolute**: Narrow-angle glaucoma. - **Relative**: Diabetes, history of stroke, peripheral vascular disease. ### Common Adverse Effects - **Very Common (>10%)**: Piloerection (goosebumps), paresthesia, pruritus (especially scalp). - **Common (1-10%)**: Supine hypertension, urinary urgency, chills, headache. - **Serious but Rare**: Bradycardia, sustained supine hypertension leading to stroke or MI, cardiac arrhythmias. ### Key Drug Interactions - **Alpha-adrenergic agonists (e.g., pseudoephedrine, phenylephrine)**: Increased risk of hypertension. Avoid concomitant use. - **Beta-blockers**: May worsen bradycardia and increase risk of supine hypertension. Monitor blood pressure and heart rate closely. - **Corticosteroids**: May potentiate pressor effects, increasing supine hypertension risk. Monitor BP. - **Bradycardia-inducing drugs (e.g., digoxin, diltiazem, verapamil)**: Increased risk of bradycardia. Monitor heart rate. ## Monitoring & Follow-up - **Before Treatment**: Supine and standing blood pressure and heart rate, renal function (CrCl). - **During Treatment**: Supine and standing blood pressure and heart rate (regularly, especially after dose changes), signs/symptoms of supine hypertension. - **Clinical Signs**: Watch for new or worsening headache, blurred vision, palpitations, or signs of urinary retention. ## Clinical Pearls - 💡 **Timing is Key**: Take doses during the day, when upright, and **at least 4 hours before bedtime**. - 💡 **Supine BP Monitoring**: Crucial to monitor supine blood pressure to prevent severe hypertension. - 💡 **Patient Counseling**: Instruct patients to report symptoms of supine hypertension (e.g., pounding in head, blurred vision) or urinary retention. - 💡 **Gradual Titration**: Start low and go slow, especially in elderly or renally impaired patients, to optimize benefit and minimize side effects. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.