Final - Beta Blockers Flashcards
Beta 1
Found in heart
Stimulation causes incr HR, cardiac contractility, AV conduction
Beta 2
Found in bronchial muscle, BVs, uterus
Stimulation causes dilation of bronchi, BVs
Beta 3
Recently IDd in mammals
Mediation of lipolysis
Beta-adrenoreceptors antagonists
- ocular
- inhibition
- classification
Topical ocular BBs (OBBs) are beta-adrenoreceptor antagonists
Competitive inhibitors
Selective (either 1 or 2)*
Non-selective (1 and 2)
*at high levels, act on all beta receptors
OBB MOA
Reduce aqueous formation
No change in outflow
Decr up to 50%
Exact mechanism unclear
OBB MOA classic hypothesis
Inhibits receptor -> stops activation of G protein -> stops stimulation of adenyl cyclase -> stops catalyzation of ATP to cAMP -> stops production of aqueous from ciliary process
OBB MOA alternate hypothesis
Ciliary process are under continuous tonic stimulation to produce aqueous (mediated by epi)
BBs interfere with tonic stimulation
OBB indications
OHT and open angle glauc
Secondary or angle closure glauc
May be standalone or with other drugs
OBB contraindications
Relative/absolute: pulmonary disease, bronchial asthma, severe COPD
-betaxolol (selective, is not contraindicated for above)0
Any pt with: sinus brady (<60bpm resting), overt CHF, hypersensitivity to drug
OBB treatment regimen
QD or BID
- BID may lower greater than QD
- more practitioners use QD and incr to BID if needed (minimize SE)
Don’t use BID:
- isatalol (QAM)
- tomoptic XE or GFs (QD)
- betagan (QD)
Timolol
- available as
- vs other BBs
- pts
Timolol maleate or hemihdrate, 0.25% or 0.5%
-maleate 0.5% commonly used
Non-selective
No corneal anesthesia (like propranolol)
Greater efficacy than pilocarpine
Lowers IOP in normals, OHT, and glaucoma pts
Timolol
- good alternative to
- onset
- peak action
- max effect
- IOP lowering persists for
Prostaglandins
30min
2 hours
Can persist for 12 hours
Persists for 24 hours
Timolol
-AM vs PM
AM reduces IOP below baseline
PM does not reduce below baseline
Timolol
-short-term escape
Not in all pts
Efficacy decr over time (several weeks)
Response of beta receptors to contstant antagonism
May be an up-regulation of receptors in target tissue
Timolol
-long-term drift
Over months-years
Control of IOP not as good as once
Washing out and re-starting helps restore levels
- clinically = 4 week wash-out period
- IOP effects may last 2 weeks
- aqueous flow up to 6 weeks
Gels vs gtts
Gels
- improve bioavailability
- decr systemic absorption
- QD instead of BID = better adherence/compliance (?)
- blurs vision
- Timoptic XE preserved with benzododecinium bromide (not BAK)
Istalol
- what it is
- claims
- efficacy
Timolol maleate 0.5%
- formulated with potassium sorbate
- lower BAK concentration
Enhances bioavailability (QD)
Most visits IOP difference is within 1.0mmHg b/w groups
-all visits within 1.5mmHg (compared to BID)
Betaxolol hydrochloride
- type
- concentration
- solution
Selective BB
0.25% suspension of resin coated beads (gradual release)
Not available in USA
Betaxolol suspension
Less ocular irritation vs solution
Less effective vs Timolol
Advantage is selective BB - can be used in pts with pulmonary disease
Local SE
- propanolol
- other OBBs
- discomfort, burning, stinging
- BAK’s purpose
Corneal anesthesia
No anesthesia
Due to active molecule, pH, preservative, vehicle
Helps with penetration
- sensitivity not uncommon
- preservative free is available, very expensive
Local SE:
- BAK issues
- metipranolol
Multiplies/exacerbates BB issues
- decr tear production
- decr goblet cell density
- dry eye symptoms
- ocular cicatricial pemphigoid
Assoc with granulomatous uveitis
Systemic SE
- how enter system
- oral dose
Via nasolacrimal system (almost like IV dose of meds)
20-60mg, OBBs do not approach oral dose
CNS adverse effects
Anxiety, depression, fatigue, lethargy, confusion, sleep disturbance, memory loss, dizziness
Sexual dysfunction
- decr libido
- impotence in men
Less CNS effects with betaxolol
Cardiovascular SE
- BBs in general
- OBBs
Blocking beta 1 = lower HR, lower BP, decr myocardial contractility, slowed conduction time
Decr HR, significant bradycardia, lower BP
- always check BP and pulse rate on pts rxd or on OBBs
- timoptic XE/other gels less effect (gels stay in the eye, less systemic absorption)
Pulmonary SE
Due to blockade of beta 2
Betaxolol has been used safely in pts with pulmonary disease
Drug-disease interaction: diabetes
- symptoms
- who is most at risk
Hypoglycemia = nervousness, sweating, intense hunger, trembling, weakness, palpitations
True problem in insulin-dependent pts
