Midodrine Hydrochloride and Prazosin Hydrochloride

• Generic Name: midodrine
• Dosage Forms: n.a.
• Other Brand Names: Proamatine, Orvaten

Treatment of symptomatic orthostatic hypotension (designated an orphan drug by FDA for this use). Indication is based on effect on increases in 1-minute standing systolic BP, a surrogate marker; clinical benefits (principally improved ability to perform life activities) not established. Continue the drug only in patients who report substantial symptomatic improvement.

Use recommended only in patients whose lives are considerably impaired despite standard clinical care; use only after nondrug therapies (e.g., support hose, increased sodium intake, life-style modifications) and fluid expansion have failed. May be more effective than comparative drugs (e.g., ephedrine) in managing postural symptoms.

In August 2010, FDA proposed to withdraw approval of midodrine because required postapproval studies verifying the clinical benefit of the drug had not been done. FDA stated that neither the original manufacturer (Shire) nor any generic manufacturer had demonstrated clinical benefit (e.g., performance of life activities); data submitted had not verified expected clinical benefit. In September 2010, FDA clarified that its proposal was part of the regulatory process and that midodrine could remain on the market as that process moves forward. Subsequently, FDA and Shire reached an agreement that Shire would conduct 2 additional clinical studies to verify the clinical benefit of midodrine in patients with symptomatic orthostatic hypotension. In February 2012, FDA announced that the proposal to withdraw approval of midodrine will be deferred until these studies have been conducted; meanwhile, the drug remains approved and available on the US market. In September 2014, FDA extended the deadline to March 31, 2015 for final submission of study results and analyses for FDA review.

• Generic Name: prazosin
• Dosage Forms: n.a.
• Other Brand Names: Minipress

Management of hypertension (alone or in combination with other classes of antihypertensive agents).

Not considered a preferred agent for initial management of hypertension according to current evidence-based hypertension guidelines, but may be useful in the management of resistant hypertension as a component of combination therapy.

Most effective when used in combination with a diuretic; beneficial effects of α1-blockers on blood glucose and lipid concentrations also may mitigate some adverse metabolic effects of diuretics.

Some experts state that an α1-blocker may be a second-line agent in antihypertensive treatment regimens in men with coexisting benign prostatic hyperplasia (BPH); however, the American Urology Association (AUA) states that monotherapy with these drugs is not optimal in hypertensive patients with lower urinary tract symptoms (LUTS) or BPH and that such conditions should be managed separately.

Individualize choice of therapy; consider patient characteristics (e.g., age, ethnicity/race, comorbidities, cardiovascular risk) as well as drug-related factors (e.g., ease of administration, availability, adverse effects, cost).

A 2017 ACC/AHA multidisciplinary hypertension guideline classifies BP in adults into 4 categories: normal, elevated, stage 1 hypertension, and stage 2 hypertension.

Source: Whelton PK, Carey RM, Aronow WS et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension. 2018;71:e13-115.

Individuals with SBP and DBP in 2 different categories (e.g., elevated SBP and normal DBP) should be designated as being in the higher BP category (i.e., elevated BP).

The goal of hypertension management and prevention is to achieve and maintain optimal control of BP. However, the BP thresholds used to define hypertension, the optimum BP threshold at which to initiate antihypertensive drug therapy, and the ideal target BP values remain controversial.

The 2017 ACC/AHA hypertension guideline generally recommends a target BP goal (i.e., BP to achieve with drug therapy and/or nonpharmacologic intervention) of <130/80 mm Hg in all adults regardless of comorbidities or level of atherosclerotic cardiovascular disease (ASCVD) risk. In addition, an SBP goal of <130 mm Hg generally is recommended for noninstitutionalized ambulatory patients ≥65 years of age with an average SBP of ≥130 mm Hg. These BP goals are based upon clinical studies demonstrating continuing reduction of cardiovascular risk at progressively lower levels of SBP.

Other hypertension guidelines generally have based target BP goals on age and comorbidities. Guidelines such as those issued by the JNC 8 expert panel generally have targeted a BP goal of <140/90 mm Hg regardless of cardiovascular risk, and have used higher BP thresholds and target BPs in elderly patients compared with those recommended by the 2017 ACC/AHA hypertension guideline.

Some clinicians continue to support previous target BPs recommended by JNC 8 due to concerns about the lack of generalizability of data from some clinical trials (e.g., SPRINT study) used to support the 2017 ACC/AHA hypertension guideline and potential harms (e.g., adverse drug effects, costs of therapy) versus benefits of BP lowering in patients at lower risk of cardiovascular disease.

Consider potential benefits of hypertension management and drug cost, adverse effects, and risks associated with the use of multiple antihypertensive drugs when deciding a patient's BP treatment goal.

For decisions regarding when to initiate drug therapy (BP threshold), the 2017 ACC/AHA hypertension guideline incorporates underlying cardiovascular risk factors. ASCVD risk assessment is recommended by ACC/AHA for all adults with hypertension.

ACC/AHA currently recommend initiation of antihypertensive drug therapy in addition to lifestyle/behavioral modifications at an SBP ≥140 mm Hg or DBP ≥90 mm Hg in adults who have no history of cardiovascular disease (i.e., primary prevention) and a low ASCVD risk (10-year risk <10%).

For secondary prevention in adults with known cardiovascular disease or for primary prevention in those at higher risk for ASCVD (10-year risk ≥10%), ACC/AHA recommend initiation of antihypertensive drug therapy at an average SBP ≥130 mm Hg or an average DBP ≥80 mm Hg.

Adults with hypertension and diabetes mellitus, chronic kidney disease (CKD), or age ≥65 years are assumed to be at high risk for cardiovascular disease; ACC/AHA state that such patients should have antihypertensive drug therapy initiated at a BP ≥130/80 mm Hg. Individualize drug therapy in patients with hypertension and underlying cardiovascular or other risk factors.

In stage 1 hypertension, experts state that it is reasonable to initiate drug therapy using the stepped-care approach in which one drug is initiated and titrated and other drugs are added sequentially to achieve the target BP. Initiation of antihypertensive therapy with 2 first-line agents from different pharmacologic classes recommended in adults with stage 2 hypertension and average BP >20/10 mm Hg above BP goal.

Benign Prostatic Hyperplasia

Has been used to reduce urinary obstruction and relieve associated manifestations in patients with symptomatic BPH; efficacy relative to other α1-adrenergic blockers remains to be established.

Posttraumatic Stress Disorder (PTSD)

Has been used in the management of PTSD, particularly in combat veterans and in patients experiencing nighttime PTSD symptoms (e.g., nightmares, sleep disturbances).

Some clinicians recommend prazosin as first-line or alternative therapy when treating PTSD patients with prominent nighttime symptoms, particularly in combat veterans. Further studies necessary in civilians with noncombat trauma-related PTSD and in treatment of daytime PTSD symptoms.