| Disadvantages to the oral route of administration include: | Emesis secondary to GI mucosal irritation, possible destruction of drug due to digestive enzymes, variability in absorption and patient compliance. |
Advantages of parenteral injection of drugs include:
| Parenteral injection may be required to deliver the drug in an active form. An example is infliximab, an antibody (protein) targeting tumor necrosis factor alpha.. This agent may be used in management of rheumatoid arthritis. Parenteral injections tend to provide more rapid drug availability and is more predictable, resulting in more accurate delivery of an effective dose. |
| Disadvantages of parenteral injections: | Parenteral administration requires sterile conditions which may be particularly challenging for intravenous and/or intrathecal administration. Furthermore, injection site pain may be an issue. |
| Controlled-release preparations--preferred applications: | Preferred applications may include management of depression and ADHD. Controlled-release may also be helpful in administration of dihydropyridine calcium entry antagonists. |
| Concerning sublingual drug administration, absorption from the oral mucosa of the mouth involves venous drainage to: | Superior vena cava |
| Some examples of drugs suitable for transdermal absorption (patch application) include: | Nicotine patches, scopolamine patches for motion sickness, nitroglycerin patches useful in managing angina pectoris, testosterone & estrogen in replacement therapy applications, various estrogens and progestins for birth control applications and fentanyl patches for management of severe pain. |
| Concerning subcutaneous drug administration, reduced absorption rates may be accomplished by adding a second agent, such as: | Epinephrine. Epinephrine may be added to the injectable local anesthetic lidocaine. Epinephrine promotes localized vasoconstriction which maintains higher lidocaine local concentration. This approach may decrease likelihood of systemic lidocaine toxicities which includes some serious CNS effects. |
| Applications of intra-arterial drug injection: | One application is in treatment of liver tumors and had-neck cancers. Diagnostic agents, Such as technetium-labeled human serum albumin may also be administered by this approach. |
| Applications for intrathecal drug administration: | To circumvent the effect of the blood-brain barrier and the blood-CSF barrier to drug access into the CSF, useful in management of acute CNS infections or in spinal anesthesia. Also, brain tumors may be treated by direct intraventricular administration of chemotherapeutic agents. |
| Characteristics of pulmonary drug absorption include: | Rapid drug access to the circulation as a result of large lung surface area. Advantages include not only nearly immediate drug absorption into the blood but also the avoidance of liver first-pass drug bioavailability loss. For treatment of pulmonary disease, pulmonary administration provides drug application at the desired site. |
| Advantages of topically applied ophthalmic agents: | Local effects represent a primary advantage. Typically systemic absorption is not desired. For example, if beta-adrenergic receptor antagonists are administered in ophthalmic drops, systemic pharmacological effects which are not desirable may occur. For instance, systemic ß antagonist drug secondary to ophthalmic use may interfere with the cardiac conduction system and may cause heart block. |
| More novel methods of drug delivery: | One example of a novel method drug delivery is drug-eluting stents which allow very localized targeting of drugs with very limited systemic effects. Sometimes systemic toxicity of drugs are decreased by combining them with a drug carrier vehicle,, modifying distribution. One example is the linkage of the cytotoxic drug calicheamicin to an antibody directed to an antigen found on the targeted leukemic cells. Another example is drug-polymer conjugates leading to stable and long-circulating protein drugs. This approach keeps the drug inactivated until released by a disease-specific trigger, usually an enzyme in the target tissue. |
| Described bioequivalence: | Drugs are considered pharmaceutically equivalent if they contain the same active ingredients and are also the same and strength concentration, dosage form, and route of administration. However, two pharmaceutically equivalent drugs are considered bioequivalent when they exhibit the same rate and extent of bioavailability of the active ingredient. Non-bioequivalence may involve oral dosage forms of poorly soluble, slowly absorbed agents, such as the urinary anti-infective drug, metronidazole-comparing generic versus tradename compounds. The generic agent was shown not bioequivalent as the method to microsize the drug for initial absorption was different from the proprietary process associated with the tradename compound. |
| A plasma protein which is a major carrier for acidic drugs: | Albumin |
| A plasma protein important in binding basic drugs: | Alpha 1-acid glycoprotein |
| This antibiotic type is prone to accumulate in bone: | Tetracycline antibiotics (as well as heavy metals) are absorbed on to the bone crystal surface and become eventually incorporated into the lattice. As such, bone can become a reservoir for the slow release of toxic agents, including letter radium into the blood. A toxic agent so localized can also lead to localized bone medulla destruction. |
| Factors that promote termination of drug action following withdrawal of the drug include: | Metabolism and excretion primarily but also may include redistribution of the drug away from its side of action and other tissues or compartments. A typical example in which rapid redistribution is the principal means of termination of drug action is highly lipid soluble intravenous anesthetic induction agent, such as thiopental or propofol. High rate of blood flow to the brain along with the drug's lipid solubility Results in rapid achievement of maximal concentration. However, upon discontinuation of the intravenous injection, thiopental rapidly leaves the brain and partitions and other tissue. |
| Distribution of drugs into the CNS from blood: | This distribution scenario is unique in part because brain capillary endothelial cells exhibit continuous tight junctions which limit entry (requiring transcellular versus paracellular transport). Characteristics of brain capillary endothelial cells and pericapillary glial cells described the blood-brain barrier. |
| Difference between the blood: CNS barrier and the blood: CSF barrier | These barriers are similar; however, in the blood-CSF case epithelial cells are joined by tight junctions rather than endothelial cells, as seen in the blood: CNS case. |
| Important physical characteristics of the drug that promote passage across the blood brain barrier: | A key factor is the lipid solubility of the non-ionized, unbound drug. Increased drug lipophilicity results in increased CNS penetration.for example, reduced lipophilicity of second generation antihistamines, e.g. loratadine, results in reduced brain concentrations compared to first-generation compounds, e.g. diphenhydramine. This difference accounts for non-sedating properties of second generation antihistamines |