The alpha receptor & HTN Flashcards
1
Q
MOA of Prazosin?
A
- Competitive antagonist of post-synaptic alpha1-receptors
2
Q
What are the effects of Prazosin?
A
- Vasodilation of veins and arterioles –> ↓ in TPR & BP
3
Q
What are the clinical applications of Prazosin?
A
- HTN
- Late choice in JNC8 d/t ALLHAT data showing > likelihood of stroke and CHF w/ doxazosin in comparison to chlorthlidone
- Off lable: PTSD related nightmares & sleep disruption; Raynaud syndrome
4
Q
What are the PKs of Prazosin?
A
- half life of 2-3 hrs
- extensively metabolized via methylation and conjugation
- eliminated in bile and feces
5
Q
Toxicities of Prazosin?
A
- Palpitations, edema, orthostatic hypotension, syncope
- Dizziness, HA, drowsiness, nervousness
- ↓ energy, weakness
- nausea, diarrhea, constipation
- Urinary frequency, “retrograde” ejaculation, priapism
- Blurred vision, reddened sclera
- Nasal congestion
6
Q
What are Tamsulosin, Terazosin, & Doxazosin?
A
Similar to Prazosin but differ in receptor selectivity; marketed for BPH and also used to help kidney stones pass
- Potential one drug soltuion for old man in wheelchair with BPH and HTN
7
Q
MOA of Clinidine?
A
- Alpha2 receptor agonist, crosses the BBB and works at the brainstem to produce desired effects
8
Q
Effects of Clonidine?
A
- IV administration –> transient ↑ in BP d/t postsynaptic alpha2 R stimulation in vascular sm m
- Stimulation of receptors in the brain stem activates inhibitory neurons that result in ↓ sympathetic outflow from the CNS –> peripheral ↓ in resistance, renal vascular resistance, HR, & BP
- Produces pain relief at spinal presynaptic postjunctional alpha2 adrenoreceptors by preventing pain signal transmission
- Benefits in ADHD by postsynaptic alpha2 agonist stimulation of subcortical activity in the prefrontal cortex to ↓ hyperactivity, impulsiveness, and distractibility
9
Q
Clinical applications of Clonidine?
A
- oral immediate release tablets or transdermal patch for management of HTN (not used as initial therapy for JNC8)
- Extended release tablets for trx of ADHD
- Continuous epidural admin w/ opioids for trx of severe cancer pain in pts tolerant or unresponsive to opioids alone; more effective for neuropathic pain and less effective for somatic or visceral pain
- Off-label: opioid withdrawal, postherpetic neuralgia, smoking cessation, Tourette syndrome
10
Q
PKs of Clonidine?
A
- Oral, transdermal, and epidermal solution formulations
- half life 12-16 hrs
- Undergoes hepatic metabolism w/ enterohepatic recirculation
- 40-60% excreted in urine as unchanged drug
11
Q
Toxicities of Clonidine?
A
- Oral, transdermal: incidence of adverse events may be less with transdermal compared to oral d/t lower peak.trough ratio
- Drowsy, HA, fatigue, dizzy, behavioral changes, vivid dreams, skin rash/dermatitis/local blanching with patch
- Xerostomia, upper abd pain
- Brady or tachy, AV block, arrhythmia, CF, CVA, CP, prolonged QT on ECG, Raynaud’s phenomenon, syncope
- Rebound HTN if dose missed
- sexual dysfunction, ↓ libido
- Accomodation disturbance, blurred vision, ↓ lacrimation, burning sensation in eyes
- NAsal congestion, nose bleeds, dry nose
12
Q
MOA of alpha-methyldopa?
A
- Selective agonist for alpha2-receptors
- Formerly considered to function as false transmitter
13
Q
Effects of alpha-methyldopa?
A
- Used as sympatholytic for HTN d/t ↓ sympathetic outflow
14
Q
Clinical applications for alpha-methyldopa?
A
- Moderate-to-severe HTN (not primary for JNC8)
- Drug of choice for gestational HTN
15
Q
PKs of alpha-methyldopa?
A
- Oral & IV
- Intestinal and hepatic metabolism
- Half life 1.5-2 hrs
- ~70% excreted in urine as parent & metabolites
