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.

Gentamicin

Gentamicin is a aminoglycoside antibiotic, and can treat many different types of bacterial infections, particularly Gram-negative infection.

Gentamicin works by binding to a site on the bacterial ribosome, causing the genetic code to be misread.

Like all aminoglycosides, gentamicin does not pass the gastro-intestinal tract, so it can only be given intravenously or intramuscularly.

Gentamicin can cause deafness or a loss of equilibrioception in genetically susceptible individuals. These individuals have a normally harmless mutation in their DNA, that allows the gentamicin to affect their cells. The cells of the ear are particularly sensitive to this.

Gentamicin can also be highly nephrotoxic, particularly if multiple doses accumulate over a course of treatment. For this reason gentamicin is usually dosed by body weight. Various formulae exist for calculating gentamicin dosage. Also serum levels of gentamicin are monitored during treatment.

E. Coli has shown some resistance to Gentamicin, despite being gram-negative

Aquaretics
An aquaretic is a class of drug that is used to promote aquaresis, the excretion of water without electrolyte loss.

Lithium, demeclocycline

Mechanism of Action

1.    Block ADH action on distal tubule and collecting duct. Blocking ADH decreases H2O permeability. H2O is not recovered (distal tubule) using osmotic draw of counter-current multiplier so aquaretics reduce water reabsorption (tubule to blood stream). 
2.    Net effect is an increase in free water clearance
 

Phenobarbital (Luminal): for generalized tonic-clonic and partial seizures (not used for absence seizures)

Mechanism: enhances GABA inhibition (↑ open time of Cl channels in presence of GABA)

Side effects: sedation, ataxia, cognitive impairment, induction of hepatic microsomal enzymes

Clavulanic acid is often combined with amoxicillin to treat certain infections caused by bacteria, including infections of the ears, lungs, sinus, skin, and urinary tract. It works by preventing bacterium that release beta-lactamases from destroying amoxicillin.

ANTICHOLINERGIC DRUGS
Blocks the action of Ach on autonomic effectors.

Classification
Natural Alkaloids - Atropine. Hyoscine

Semi-synthetic deriuvatives:- Homatropine, Homatropine methylbromide, Atropine methonitrate.

Synthetic compounds 

(a) Mydriatics - Cyclopentolate. Tropicamide.
(b) Antisecretory - Antispasmodics - Propantha1ine. Oxy-phenonium, Pirenzipine.
c) Antiparkinsonism- Benzotopine, Ethopropazine, Trihexyphenidyl, Procyclidine, Biperiden 
Other drugs with anticholinergic properties • Tricyclic Antidepressants • Phenothiazines • Antihistaminics • Disopyramide

MUSCARINIC RECEPTORS SUBTYPES & ANTAGONISTS 
• M 1 Antagonists – Pirenzepine, Telenzepine, dicyclomine, trihexyphenidyl 
• M 2 Antagonists – Gallamine, methoctramine 
• M 3 Antagonists – Darifenacin, solifenacin, oxybutynin, tolterodine

Pharmacological Actions
CNS - stimulation of medullary centres like vagal. respiratory. vasomotor and inhibition of vestibular excitation and has anti-motion sickness properties.
CVS - tachycardia.
Eye - mydriasis
Smooth muscles - relaxation of the muscles receiving parnsympathetic motor innervation.
Glands - decreased secretion of sweat and salivary glands
Body Temperature - is increased as there is stimulation of  temperature regulating centre.
Respiratory System- Bronchodilatation & decrease in secretions. For COPD or Asthma - antimuscarinic drugs are effective
GIT - Pirenzepine & Telenzepine - decrease gastric secretion with lesser side effects.