Nonselective Alpha Agonists

• These drugs bind to alpha receptors 

Adverse Effects

• CNS: anxiety, restlessness, depression, blurred vision/light sensitivty (from pupil dilation)
• CV: arrhythmia, ECG changes, BP changes 
• GU: dec UO, difficulty urinating

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Drugs
1. Phenylephrine (Neo-Synephrine)

• potent vasoconstrictor – works on alpha-1 receptors
• has little to no effect on heart & bronchi

Indications

• Parenterally: shock/shock-like state, SVT, prolong local anesthesia, maintain BP during spinal anesthesia use
• Topically: ophthalmic; to ↓ IOP associated w/ glaucoma; dilates pupils during eye exam or surgery
• Nasal Spray: used topically to treat allergic rhinitis & receive Sx otitis media
• Other: Intracavernosal Phenylephedrine is the drug of choice & first line Tx of low-flow priapism b/c it has almost pure alpha effects & minimal beta activity

Caution:

• essential HTN
• used in many OTC meds, may cause inadvertent OD

AE:

• fear, anxiety, restlessness
• headache, nausea, pallor
• ↓ urine formation

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2. Midodrine (ProAmantine)

• orthostatic hypotension (non-responsive to normal therapies)
• works on alpha-1 receptors

3. Clonidine (Catapres)

• centrally-acting alpha-2 agonists (stimulates A2 CNS receptors)
• they are hypotensive agents – ↓ HR, inhibit NE

Indications

• indicated for essential HTN
• epidural infusion for Tx chronic pain in terminally ill adults
• can be used to treat high BP, ADHD, anxiety/panic disorders

Caution:

• do not stop suddenly! - taper over 2-4 days
• fall risk (monitor BP closely - esp. w/ postural change)

AE:

• hallucinations, bad dreams
• headache, sedation, fatigue
• dry mouth, dec sexual function
• N/V, constipation
• can cause extreme hypotension, brady, HF

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