Respiratory Drugs Flashcards
Albuterol
Selective B2 adrenergic Receptor Antagonist
B2»B1 (200 - 400 times)
Uses;
- Asthma
- COPD
- Prevention pf exercise induced asthma
- Tx acute bronchospasm
- Pre-op for bronchodilation in at risk pts (smokers, asthmatics, atopic pts)
- Tx hyperkalemia (increase K uptake by skeletal muscles)
MOA;
- binds to B2»»>B1 and activates the G protein coupled receptor cascade (G alpha S) increasing cAMP causing smooth muscle relaxation and bronchodialtion
- bulky structure added to catecholamine to provide B2 selectivity and prevent metabolism from COMT making it longer acting
Dose; -MDI; 90 - 100 mcg/puff -Blunt Airway response to intubation in asthmatics; 2- 4 puffs -Acute bronchospasm; 4 -8 puffs q 20 min x 3 then q 1-4 hrs
Pharmacokinetics;
- onset; 5min
- peak; 30 – 60 min
- E1/2t; 3 -5 hours
- DOA; 4 – 8 hrs
metabolized by the liver NOT COMT (makes it longer acting)
30% excrete unchanged in urine
Side Effects; usually r/t systemic absorption -tremor (B2 stim in skeletal muscles) -tachycardia reflex r/y dilation (high dose; some B1 stim) -hyperglycemia -hypokalemia -hypomagnesium -tachyphylaxis with chronic use from down regulation of receptors
Contraindicated;
-hypersensitivity
Caution
- CAD
- MAOi, TCAs and sympathomimetics can increase SE
- MDI in the presence of a tracheal tube decreases amount of drug to the trachea 50 -70%
Terbutaline
Non-catecholamine
Beta2 adrenergic receptor antagonist
Uses;
- Bronchospasm
- COPD
- Acute asthma exacerbation
- infusion in pedi pts with status asthmatics r/t respiratory failure
- Tx preterm labor (relax uterus
- Antagonizes Hypoxic PulmonaryVasoconstriction (HPV)
- Prevent exercise induced asthma (take 10 -15 min before)
MOA;
-binds to B2 receptor stimulates the G protein receptor cascade (G alpha S); increases cAMP; in the lungs cAMP decreases intracellular Ca, increases K conductance and causes smooth muscle relaxation/ bronchodilation
Dose;
SQ dose; 0.25 mg can repeat in 15 - 30 min; max SQ dose in 4 hrs is 0.5 mg
MDI; 200 mcg/puff
do not exceed 16 - 20 puffs QD
Pharmacokinetics; -1/2 life; 16 hrs -Inhaled DOA; 2 -2.5 hrs -SQ DOA; 1.5 -4 hrs -Pb;25% Non- catecholamine; No hyroxyl group onC 3,4 of the benzene ring -metabolized by MAO in the liver not metabolized by COMT -50% eliminated unchanged in urine (check creatinine Clarence for dosing)
Side Effects; -tremor (B2 stim in skeletal muscles) -CNS excitation Systemic effects; -tachycardia (reflex to dilation) -hyperglycemia -hypomagnesium -hypokalemia -arrhythmias (r/t low K) -tachyphylaxis (down regulation of B receptors
Contraindication;
- hypersensitivity
- Renal Failure creatinine clearance < 10mL/min
- MAOis
Caution
-Renal Failure; decrease dose 50% if creatinine Clarence is 10 -50 ml/min
Theophylline
Methylxanthines (adenosine receptor antagonist)
Phosphodiesterase Inhibitors
Bronchodilator
Uses;
-Asthma
-COPD
-Tx apnea of prematurity (increases sensitivity of medullary respiratory center to C02 stimulate respiratory drive)
*No added bronchodilatory effect during maintenance of anesthesia
theophylline has be replaced by B2 agonists for treating asthma induced bronchospasm
MOA; not clear but the end effect is airway relaxation and bronchodilation
- adenosine receptor antagonist release of catecholamines
- at high concentrations inhibits phosphodiesterase enzymes; preventing breakdown of cAMP in airway smooth muscles and inflammatory cells
- inhibition of inflammation
Dose; 5 mg/kg (PO)
available in sustained release formulation only
IV form must be given slow; risk of seizures
Pharmacokinetics;
- peak plasma concentration 1 -2 hrs
- ½ life; wide variation
- metabolized in liver by CYP450 (smokers metabolize drug 50% faster)
- in premature infants metabolized into caffeine; and clearance is prolonged
- excreted in urine by the kidney
- narrow therapeutic plasma level; 10 – 20 mg/ml
- Toxic at >20mg/ml
Side Effects; (almost always at toxic levels > 20mg/ml) Therapeutic plasma level: 10-20 mg/ml
- Cardiac arrhythmias (drug induced release of catecholamine from the adrenal)
- Hypotension
- death from CV collapse
- CNS stimulation (indicated toxicity); nervousness, tremor, irritability, N/V
- Insomnia
- Seizures with higher concentrations of rapid IV administration
- Brain damage
- Hyperglycemia
- Hypokalemia
- Charcol given to stop absorption, lidocaine to treat arrythmia and benzos to treat seizures
Caution;
- Ketamine may decrease the seizure threshold
- theophylline can partially antagonize NMBD (may need to give more)
- increased theophylline level; Cimetidine, Cipro, & antifungals (-azole) (CYP450 inhibitors)
- decreased theophylline level; Phenobarbital & phenytoin (CYP inducers) decrease levels
- Caffeine is a methylxanthine & can increase theophylline levels (promote CNS & CV toxicity)
*Higher dose of Benzos might be needed in the presence of theophylline
benzos increase CNS concentration of adenosine (potent CNS depressant)
theophylline inhibit adenosine at the adenosine receptors (CNS stimulant)
Ipratropium
Anticholinergic, muscarinic receptor antagonist
Quaternary ammonium (atropine derivative; does NOT cross BBB)
Uses;
-Bronchodilator
-COPD maintenance therapy
-Rescue therapy for asthma and COPD
*Not for routine use I asthma
-Tx to increase exercise tolerance, decreases dyspnea and improve gas exchange
MOA;
-Antagonizes the effect of endogenous acetylcholine at M3 receptor subtypes casusing smooth muscle relaxation/ bronchodilation
Dose;
MDI: 40 - 80mcg in 2-4 puffs
Pharmacokinetics;
- onset: slow 30 - 90 minutes
- DOA: 4-6 hours
- Not significantly absorbed compared to atropine
Side Effects;
- poorly absorbed serious side effects not common
- Inadvertent oral absorption can cause urinary retention, dry mouth and GI upset
- inadvertent exposure to eyes can cause Pupil dilation/ blurred vision
Contraindications;
-carcinoid tumor (tumor that secrets vasoactive substances causing bronchoconstriction typically resistant to B agonist treatment; Ipratropium may exacerbate the problem)
