ANTIASTHMATIC AGENTS

 Classification for antiasthmatic drugs.
 
I. Bronchodilators

i. Sympathomimetics (adrenergic receptor agonists)

Adrenaline, ephedrine, isoprenaline, orciprenaline, salbutamol, terbutaline, salmeterol, bambuterol

ii. Methylxanthines (theophylline and its derivatives)

Theophylline 
Hydroxyethyl theophylline 
Theophylline ethanolate of piperazine

iii. Anticholinergics

Atropine methonitrate 
Ipratropium bromide

II. Mast cell stabilizer

Sodium cromoglycate
Ketotifen 

III. Corticosteroids

Beclomethasone dipropionate 
Beclomethasone (200 µg) with salbutamol

IV. Leukotriene pathway inhibitors 

Montelukast 
Zafirlukast

Beta-Adrenergic blocking Agents 

• Prototype - Propranolol 
• Prevent or inhibit sympathetic stimulation
– Reduces heart rate
– Myocardial contractility 
– Reduce BP - decreases myocardial workload and O2 demand 
• In long-term management used to decrease frequency and severity of anginal attacks 
• Added when nitrates do not prevent anginal episodes 
• Prevents exercise induced tachycardia
• Onset of action 30 min after oral dose. 1-2 min IV

Therapeutic Actions
• Block Beta adrenergic receptors in the heart and juxtaglomerular apparatus 
• Decrease the influence of the sympathetic nervous system decreasing excitability of the heart 
• Decrease cardiac output. 
• Indicated for long term management of anginal pectoris caused by atherosclerosis 

Atenolol, metoprolol, and nadolol have the same actions, uses, and adverse effects as propranolol, but they have long half-lives and can be given once daily. They are excreted by the kidneys, and dosage must be reduced in clients with renal impairment.

Mefenamic acid

Analgesic, anti‐inflammatory properties less  effective than aspirin 

Short half‐lives, should not be used for longer  than one week and never in pregnancy and in  children. 

Enhances oral anticoagulants

Used to treat pain, including menstrual pain. It decreases inflammation (swelling) and uterine contractions.

On the basis of Receptors, drugs can be divided into four groups,

a. agonists

b. antagonists

c. agonist-antagonists

d. partial agonists

a. Agonist

morphine fentanyl pethidine

Action : activation of all receptor subclasses, though, with different affinities

b. Antagonist

Naloxone , Naltrexone

Action :  Devoid of activity at all receptor classes  

c. Partial Agonist: (Mixed Narcotic Agonists/Antagonists)

Pentazocine, Nalbuphine, Butorphanol , Buprenorphine

Action: activity at one or more, but not all receptor types

With regard to partial agonists, receptor theory states that drugs have two independent properties at receptor sites,

a. affinity

The ability, or avidity to bind to the receptor
Proportional to the association rate constant, Ka

b. efficacy

or, intrinsic activity, and is the ability of the D-R complex to initiate a pharmacological effect

Drugs that produce a less than maximal response and, therefore, have a low intrinsic activity are called partial agonists.

These drugs display certain pharmacological features,

a. the slope of the dose-response curve is less than that of a full agonist

b. the dose response curve exhibits a ceiling with the maximal response below that obtainable by a full agonist

c. partial agonists are able to antagonise the effects of large doses of full agonists

GLP-1 analogs

Exenatide

Mechanism

GLP-1 is an incretin released from the small intestine that aids glucose-dependent insulin secretion
basis for drug mechanism is the observation that more insulin secreted with oral glucose load compared to IV 

Exenatide is a GLP-1 agonist

↑ insulin
↓ glucagon release
the class of dipeptidyl peptidase inhibitors ↓ degradation of endogenous GLP-1
e.g.) sitagliptin, -gliptins 
 

Clinical use
type II DM
 

Toxicity
nausea, vomiting
pancreatitis
hypoglycemia
if given with sulfonylureas

Seizure classification:

based on degree of CNS involvement, involves simple ( Jacksonian; sensory or motor cortex) or complex symptoms (involves temporal lobe)

1.    Generalized (whole brain involved): 

a.    Tonic-clonic:

Grand Mal; ~30% incidence; unconsiousness, tonic contractions (sustained contraction of muscle groups) followed by clonic contractions (alternating contraction/relaxation); happens for ~ 2-3 minutes and people don’t breathe during this time

Drugs: phenytoin, carbamazepine, Phenobarbital, lamotrigine, valproic acid

Status epilepticus: continuous seizures; use diazepam (short duration) or diazepam + phenytoin

b.    Absence:

Petit Mal; common in children; frequent, brief lapses of consciousness with or without clonic motor activity; see spike and wave EEg at 3 Hz (probably relates to thalamocorticoreverburating circuit)

Drugs: ethosuximide, lamotrigine, valproic acid

c.    Myoclonic: uncommon; isolated clinic jerks associated with bursts of EEG spikes; 

Drugs: lamotrigine, valproic acid

d.    Atonic/akinetic: drop seizures; uncommon; sudden, brief loss of postural muscle tone
Drugs: valproic acid and lamotrigine

2.    Partial:  focal

a.    Simple:  Jacksonian; remain conscious; involves motor or sensory seizures (hot, cold, tingling common)

Drugs: carbamazepine, phenytoin, Phenobarbital, lamotrigine, valproic acid, gabapentin

b.    Complex: temporal lobe or psychomotor; produced by abnormal electrical activity in temporal lobe (involves emotional functions)

Symptoms: abnormal psychic, cognitive, and behavioral function; seizures consist of confused/altered behavior with impaired consciousness (may be confused with psychoses like schizophrenia or dementia)

Drugs: carbamazepine, phenytoin, laotrigine, valproic acid, gabapentin

Generalizations: most seizures can’t be cured but can be controlled by regular administration of anticonvulsants (many types require treatment for years to decades); drug treatment can effectively control seizures in ~ 80% of patients