DESCRIPTION :
This compound belongs to the class of organic compounds
known as resorcinols. These are compounds containing a resorcinol moiety, which
is a benzene ring bearing two hydroxyl groups at positions 1 .
- CATEGORY
Sympathomimetics
Adrenergic beta-2 Receptor
Agonists
Bronchodilator Agents
Tocolytic Agents
Respiratory System
Drugs for Obstructive Airway
Diseases
Selective Beta-2-Adrenoreceptor
Agonists
Adrenergics, Inhalants
Adrenergics for Systemic Use
Beta2 Agonists
PHARMACODYNAMICS :
Terbutaline is a relatively selective beta2-adrenergic
bronchodilator that has little or no effect on alpha-adrenergic receptors. The
drug has exerts a preferential effect on beta2-adrenergic receptors but
stimulates beta-adrenergic receptors less selectively than relatively selective
beta2-agonists. Terbutaline appears to have a greater stimulating effect on
beta-receptors of the bronchial, vascular, and uterine smooth muscles (beta2
receptors) than on the beta-receptors of the heart (beta1 receptors). This drug
relaxes smooth muscle and inhibits uterine contractions, but may also cause
some cardiostimulatory effects and CNS stimulation.
MECHANISM OF ACTION :
The pharmacologic effects of terbutaline are at least in
part attributable to stimulation through beta-adrenergic receptors of
intracellular adenyl cyclase, the enzyme that catalyzes the conversion of
adenosine triphosphate (ATP) to cyclic- 3',5'- adenosine monophosphate (c-AMP).
Increased c-AMP levels are associated with relaxation of bronchial smooth muscle
and inhibition of release of mediators of immediate hypersensitivity from
cells, especially from mast cells.
PHARMACOKINETIC PROPERTY
:
Absoption: Approximately 30-50% if administered orally and well
absorbed subcutaneously.
Route of elimination:About 90% of the drug was excreted in the urine at 96 hours
after subcutaneous administration, with about 60% of this being unchanged drug.
It appears that the sulfate conjugate is a major metabolite of terbutaline and
urinary excretion is the primary route of elimination
Half life : 5.5-5.9 hours
Clearance: 311
+/- 112 mL/min
Terbutaline Sulfate: Oral LD50(rat) = 8.7 g/kg; Oral
LD50(mouse) = 205 mg/kg; Oral LD50(dog) = 1.5 g/kg; IP LD50(rat)= 220 mg/kg ;
IP LD50(mouse) = 130 mg/kg; Oral LD50(rabbit) = >8 g/kg; IV LD50(mouse) = 36
mg/kg; IV LD50(dog) = 116 mg/kg; IV LD50(rabbit) = 110 mg/kg
Affected organisms: Humans
and other mammals
DRUG –DRUG INTERACTION:
Acebutolol + Terbutaline :
The risk or severity of adverse effects can be increased when
Acebutolol is combined with Terbutaline.
Acetaminophen + terbutaline :
The risk or severity of adverse effects can be increased
when Terbutaline is combined with Acetaminophen.
Acetylsalicylic acid + terbutaline
The risk or severity of adverse effects can be increased
when Terbutaline is combined with Acetylsalicylic acid.
Aminophylline + terbutaline :
The risk or severity of adverse effects can be increased
when Terbutaline is combined with Aminophylline.
Amitriptyline + terbutaline :
The risk or severity of adverse effects can be increased
when Amitriptyline is combined with Terbutaline.
Amphetamine + terbutaline:
The risk or severity of adverse effects can be increased
when Terbutaline is combined with Amphetamine.
THERAPEUTIC USES :
Terbutaline is used to treat wheezing and shortness of
breath from lung problems (e.g., asthma, chronic obstructive pulmonary disease,
bronchitis and emphysema). Controlling these symptoms can decrease time lost
from work or school. Terbutaline is a bronchodilator (beta-2 receptor agonist)
that works by opening breathing passages to make breathing easier.
SIDE EFFECTS :
Nervousness
Restlessness
Panic
REFERENCE:-Tripathi K D"Essential of medical pharmacology",7th edition ,page no.133,223
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