McKenna's Pharmacology for Nursing, 2e

E

Appendix

Vitamins

V itamins are substances that the body requires for carrying out essential metabolic reactions. The body cannot synthesise enough of these components to meet all of its needs; therefore, they must be obtained from animal and vege- table tissues taken in as food. Vitamins are only needed in small amounts because they function as coenzymes that activate the protein portions of enzymes, which catalyse a great deal of biochemical activity. Vitamins are either water soluble and excreted in the urine or they are fat soluble and capable of being stored in adipose tissue in the body.

Care considerations

Assessment

■ ■ Obtain a nutritional assessment. Screen for any medical conditions and drugs being taken and for any known allergies. ■ ■ Evaluate skin and mucous membranes, as well as pulse, respirations and blood pressure. Full blood count (FBC) and clotting times may need to be evaluated with specific vitamins. Implementation ■ ■ Assess the person’s general physical condition before beginning test to decrease the potential for adverse effects and ensure need for the drug. ■ ■ Advise the person to avoid the use of over-the- counter preparations that contain the same vitamins to prevent inadvertent overdose of the vitamin. ■ ■ Provide comfort measures to help the person tolerate drug effects (e.g. take drug with meals to alleviate gastrointestinal distress). ■ ■ Include information about the solution being used in a test (e.g. what to expect, adverse effects that may occur, follow-up tests that may be needed) to enhance knowledge about drug therapy and promote compliance with drug regimen. Evaluation ■ ■ Monitor response to the drug (adequate vitamin intake). ■ ■ Evaluate the effectiveness of the teaching plan (person can name adverse effects to watch for and specific measures to avoid them; person understands the importance of follow-up that will be needed). ■ ■ Monitor the effectiveness of comfort measures and compliance with the regimen. ■ ■ Monitor for adverse effects (GI upset).

Therapeutic actions and indications Vitamins act as coenzymes to activate a variety of proteins on enzymes that catalyse biochemical activity. They are indicated for the treatment of vitamin deficien- cies, as dietary supplements when needed and as specific therapy related to the activity of the vitamin. Contraindications and cautions These drugs are contraindicated in the presence of any known allergy to the drug or the colourants, additives or preservatives used in the drug. Some are used to maintain adequate vitamin levels during pregnancy and breastfeeding. Adverse effects The adverse effects primarily associated with these drugs are related to gastrointestinal upset and irritation, which is caused by direct gastrointestinal contact with the drugs. Clinically important drug–drug interactions Pyridoxine—vitamin B 6 —interferes with the effec- tiveness of levodopa. Fat-soluble vitamins may not be absorbed if given concurrently with mineral oil, cholestyramine or colestipol.