Drugs December Midterm - Pharm

Buprenorphine is a partial agonist and opiod analgesic. Partial agonist means it is normally an agonist but also acts as an antagonist in the presence of a full agonist (blocking its effect).

- lower abuse potential.

- lower physical dependence

- greater safety from overdose

(Gen Principles)

Pindolol is a partial agonist used for high blood pressure and abnormal heart rhythms. Partial agonist means it is normally an agonist but also acts as an antagonist in the presence of a full agonist (blocking its effect).

- Reduces excessive stimulation due to norepinephrine in a person with high sympathetic nervous system activity.

(Gen Principles)

No, aminoglycosides like streptomycin and gentamycin are too polar to cross cell membranes. They are injected for this reason.

(Gen Principles)

No, these three medications (nitro, noradrenaline, insulin) are examples of drugs that are ineffective when given orally because of poor absorption. They need to be given parenterally (ie anything not oral).

(Gen Principles)

No, amines such as dopamine and serotonin have limited penetration across the blood-brain barriers. However, the dopamine precursor L-dopa can be given instead and metabolized in the brain.

(Gen Principles)

Lipid soluble barbituate; anesthetic. Thiopental is given in small continuous doses because redistribution initially favors the brain/kidney (high blood flow) before being sequestered into skin/fat (storage). This allows rapid anesthetic and recovery, compared to a "regular" initial dose that would be prolonged.

(Gen Principles)

Proton pump inhibitors. Omeprazole & Lansoprazole are also prodrugs, and are metabolized into their drug form.

(Gen Principles)

Osalazine is a prodrug, metabolized to the active drug mesalamine for the treatment of inflammatory bowel disease.

(Gen Principles)

Herbal antidepressent. St John's Wort is also an example of an inducer of CYP enzymes. This means other drugs metabolized by CYP enzymes can have lower than expected concentrations and cause treatment failure. Other inducers of CYP enzymes include Rifampin (antibiotic) and Barbituates.

(Gen Principles)

Cimetidine is a stomach acid inhibitor. It is also an example of an inhibitor of CYP enzymes. This means other drugs metabolized by CYP enzymes can have higher than expected concentrations and cause drug toxicity. Other inhibitors of CYP enzymes include grapefruit juice, erythromycin (antibiotic), and Itraconazole (antifungal).

(Gen Principles)

Botulinum causes skeletal muscle paralysis because it blocks Ach release at msk junctions.

Norepinephrine stimulates both alpha and beta adrenergic receptors (B1>B2). This causes a broad sympathetic response. Differences from normal sympathetic:

- Vessels all contract; the ones that vasodilate from B2 receptors do so in presence of epinephrine but not norpeinephrine.

- Since B2 receptors relax bronchial smooth muscle, we do not get the effect with norepinephrine as we would with epinephrine or albuterol.

- Since B2 receptors cause liver glycogenolysis and gluconeogenesis, norepinephrine does not cause this.

- Since B2 receptors cause uterine relaxation, norepinephrine does not cause this.

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Carbachol and pilocarpine are muscarininc receptor agonists. Therefore they mimick parasympathetic effects.

Neostigmine is an acetylcholinesterase inhibitor. It delays breakdown of Ach and prolongs its action. It therefore mimicks parasympathetic responses. Neostigmine is a reversible inhibitor of AchE (3-4 hrs).

Atropine is a muscarininc receptor antagonist. It therefore blocks parasympathetic responses.

D-tubocurarine is a skeletal neuromuscular junction blocker. It therefore blocks parasympathetic effects.

These are four Choline esters, acting therefore as muscarinic receptor agonists.

- Carbachol and Bethanechol are relatively resistant to hydrolysis by AchE, prolonging their action compared to Ach.

Muscarine and Pilocarpine are plant alkaloids. They act as muscarinic receptor agonists.

Pilocarpine is a muscarinic receptor agonist (parasympathetic). It is used in eye drop form (better tolerated than anticholinesterases) to contract ciliary muscle, which opens up the trabecular meshwork to facilitate outflow of aqueous. They are also used in narrow angle glaucoma to cause miosis (pupillary constriction) and facilitate drainage of aqueous humor.

Oral pilocarpine can treat xerostomia (dry mouth) in Sjogren's syndrome or following head and neck irradiation. It will cause excessive sweating in addition to the salivary/lacrimal secretions.

Bethanechol is a muscarinic receptor agonist (parasympathetic). It is used in some cases of postoperative abdominal distension, gastric atony, gastroparesis, congenital megacolon, and postoperative ileus (hypomotility). Bethanechol is also used in urinary retention (postoperative and postpartum) and for hypotonic bladder.

Edrophonium is a reversible ChE inhibitor. It will increase cholinergic activity where it is decreased. This assists in GI motility, urinary bladder, skeletal muscle contraction, Alzheimer's, etc. Other reversible ChE inhibitors include neostigmine, physostigmine, and pyridostigmine.

Donepezil and tacrine are reversible ChE inhibitors that happen to have high affinities and partition into lipids. They are used for Alzheimer's disease (along with rivastigmine and galantamine).

These are ChE inhibitors.

Botulinum blocks Ach release. It paralyzes sksletal muscles for use in cases of excessive involuntary skeletal muscle tone. Clinically, that's good for strabismus, blepharospasm, and hemifacial spasm. Cosmetically, it removes wrinkles.

Atropine and Scopolamine are muscarinic cholinergic receptor blockers (parasympathetic blocker). These two are belladonna alkaloids. Muscarinic cholinergic receptor blockers are used in:

- motion sickness (M1 receptor in vestibular apparatus)

- Mydraisis for examination of the retina & inflammatory uvetitis

- Reducing GI motility for irritable bowel syndrome or decreased gastric acid secretion.

- Reducing contractility of urinary tract and bladder for urinary incontinence

- Bronchodilation for COPD

- Parkinson's disease

Oxybutynin is a muscarinic cholinergic receptor blocker (parasympathetic blocker). This drug is a semisynthetic / synthetic.

Atropine is a well tolerated muscarinic cholinergic receptor blocker. It is absorbed orally and also reaches the brain. Effects last longer at the eye because of binding to iris pigment and slowly releasing drug. Increasing doses of atropine produce increasing block of parasympathetic effects:

- Depress salivary and bronchial secretions and sweating

- Pupil dilates, accomodation of eye inhibited, HR increases

- Tone and motility of GI tract and urinary bladder are inhibited.

- Gastric acid secretion and motility are inhibited.

- Atropine blocks Ach more readily at sites where less neurotransmitted is released! (salivary glands >>> SA node).

- Low doses of scopolamine are more sedative than low doses of atropine.

Scopolamine is well absorbed orally and reaches the brain more readily than atropine (10x more potent CNS as well!).

- Scopolamine is used for motion sickness as a transdermal patch behind the ear. More of it is present in a unionized form at physiological pH than atorpine, promoting absorption through the skin.

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