Routes of Drug Administration

Intravenous

• No barriers to absorption since drug is put directly into the blood.
• There is a very rapid onset for drugs administered intravenously.  This can be advantagous in emergency situations, but can also be very dangerous.
• This route offers a great deal of control in respect to drug levels in the blood.
• Irritant drugs can be administer by the IV route without risking tissue injury.
• IV drug administration is expensive, inconvenient and more difficult than administration by other routes.
• Other disadvantages include the risk of fluid overload, infection, and embolism.  Some drug formulations are completely unsafe for use intravenously.

Intramuscular:

• Only the capillary wall separates the drug from the blood, so there is not a significant barrier to the drug's absorption.
• The rate of absorption varies with the drug's solubility and the blood flow at the site of injection.
• The IM route is uncomfortable and inconvenient for the patient, and if administered improperly, can lead to tissue or nerve damage.

Subcutaneous

Same characteristics as the IM route.

Oral

• Two barriers to cross: epithelial cells and capillary wall.  To cross the epithelium, drugs have to pass through the cells.

• Highly variable drug absorption influenced by many factors:  pH, drug solubility and stability, food intake, other drugs, etc.
• Easy, convenient, and inexpensive.  Safer than parenteral injection, so that oral administration is generally the preferred route.
• Some drugs would be inactivated by this route
• Inappropriate route for some patients.
• May have some GI discomfort, nausea and vomiting.
• Types of oral meds = tablets, enteric-coated, sustained-release, etc.
• Topical, Inhalational agents, Suppositories

Ketamine 
- Causes a dissociative anesthesia.
- Is similar to but less potent than phencyclidine.
- Induces amnesia, analgesia, catalepsy and anesthesia, but does not induce convulsions.
- The principal disadvantage of ketamine is its adverse psychic effects during emergence from anesthesia. These include: hallucinations, changes in mood and body image.
- During anesthesia, many of the protective reflexes are maintained, such as laryngeal, pharyngeal, eyelid and corneal reflexes.
- Muscle relaxation is poor.
- It is not indicated for intracranial operations because it increases cerebrospinal fluid pressure.
- Respiration is well maintained.
- Arterial blood pressure, cardiac output, and heart rate are all elevated.

Ketoprofen

It acts by inhibiting the body's production of prostaglandin.

Monoamine oxidase inhibitors (MAOIs) 

e.g. phenelzine, tranylcypromine, moclobemide

- Belong to first generation antidepressants with TCAs
- Most MAOIs irreversibly inhibit the intraneuronal catabolism of norepinephrine and serotonin by MAO-A and MAO-B
- increase brain levels of noradrenaline and 5-HT
- Moclobemide causes selective, reversible inhibition of MAO-A

DRUG INTERACTIONS

Hypertensive crises similar to cheese reaction with OTC cough/cold preparations containing indirect-sympathomimetics
e.g. ephedrine

- Other antidepressants should not be started at least 2 weeks after stopping MAOIs and vice versa due to risk of serotonin syndrome
- Similar interaction with pethidine

ADVERSE DRUG REACTIONS

- Antimuscarinic side effects (e.g. dry mouth, blurred vision, urinary retention)vision, urinary retention)
- Excessive central stimulation causes tremors, excitement and insomnia
- Postural hypotension
- Increased appetite with weight gain

Ciprofloxacin : Ciprofloxacin is bactericidal and its mode of action depends on blocking of bacterial DNA replication by binding itself to an enzyme called DNA gyrase

Ciprofloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and  Gram-negative bacteria.

Enterobacteriaceae, Vibrio,  Hemophilus influenzae, Neisseria gonorrhoeae

 Neisseria menigitidis,  Moraxella catarrhalis,  Brucella, Campylobacter,

 Mycobacterium intracellulare, Legionella sp., Pseudomonas aeruginosa,

Bacillus anthracis - that causes anthrax

Weak activity against: Streptococcus pneumoniae,

No activity against:  Bacteroides,  Enterococcus faecium, Ureaplasma urealyticum  and others

It is contraindicated in children, pregnancy, and epilepsy.

Ciprofloxacin can cause photosensitivity reactions and can elevate plasma

theophylline levels to toxic values. It can also cause  constipation and sensitivity to caffeine.

Dosage in respiratory infections is 500-1500 mg a day in 2 doses.

Erythromycin

used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including  mycoplasma. It is also used to treat outbreaks of chlamydia, syphilis, and gonorrhea.

Erythromycin is produced from a strain of the actinomyces Saccaropolyspora erythraea, formerly known as Streptomyces erythraeus.