Metronidazole

(me troh Ni da zohl)

Introduced: 1960

Prescription: USA: Yes Canada: Yes

Available as Generic: Yes

Class: Anti-infective

Controlled Drug: USA: No Canada: No

Brand Names: Apo-Metronidazole, Flagyl, Metizol, MetroGel, Metryl, Neo-Tric, Novonidazole, PMS-Metronidazole.

Principal Uses

As a Single Drug Product: Used primarily to treat trichomonas infections of the vaginal canal and cervix and of the male urethra. It is also used to treat amebic dysentery, giardia infections of the intestine and serious infections caused by certain strains of anaerobic bacteria. A more recent use is the treatment of rosacea with local application of a gel dosage form.

How This Drug Works: By interacting with DNA, this drug destroys essential components of the nucleus that are necessary for the cell life and growth of infecting organisms.

Available Dosage Forms and Strengths

Gel — 0.75%

Injection — 500 mg per 100 ml

Tablets — 250 mg, 500 mg

Usual Adult Dosage Range: Varies with infection to be treated.

For trichomoniasis: One-day course—2 grams as a single dose; or 1 gram for 2 doses 12 hours apart. Seven-day course—250 mg 3 times/day for 7 consecutive days. (The 7-day course is preferred.)

For amebiasis: 500 to 750 mg 3 times/day for 5 to 10 consecutive days.

For giardiasis: 2 grams once/day for 3 days; or 250 to 500 mg 3 times/day for 5 to 7 days.

The total daily dosage should not exceed 4 grams (4000 mg).Note: Actual dosage and administration schedule must be determined by the physician for each patient individually.

Dosing Instructions: May be taken with or following food to reduce stomach irritation. The tablet may be crushed for administration.

Usual Duration of Use: Continual use on a regular schedule as outlined is necessary to ensure this drug's effectiveness. Do not repeat the course of treatment without your physician's approval.

This Drug Should Not Be Taken If

• you have had an allergic reaction to it previously.

• you currently have a bone marrow or blood cell disorder.

• you have any type of central nervous system disorder, including epilepsy.

Inform Your Physician Before Taking This Drug If

• you have a history of any type of blood cell disorder, especially one induced by drugs.

• you have impaired liver or kidney function.

• you are pregnant or breast-feeding.

Possible Side-Effects (natural, expected and unavoidable drug actions) A sharp, metallic, unpleasant taste. Dark discoloration of the urine (of no significance). Superinfection by yeast organisms in the mouth or vagina.

Possible Adverse Effects (unusual, unexpected and infrequent reactions) If any of the following develop, consult your physician promptly for guidance.

Mild Adverse Effects

Allergic Reactions: Skin rash, hives, flushing, itching.

Headache, dizziness, incoordination, unsteadiness.

Loss of appetite, nausea, vomiting, abdominal cramps, diarrhea.

Irritation of mouth and tongue, possibly due to yeast infection.

Serious Adverse Effects

Idiosyncratic Reactions: Abnormal behavior, confusion, depression.

Peripheral neuropathy.

Abnormally low white blood cell count (transient): fever, sore throat, infections.

Possible Effects on Sexual Function: Decreased libido; decreased vaginal

secretions (difficult or painful intercourse).

Possible Delayed Adverse Effects: Studies have shown that this drug can cause cancer in mice and possibly in rats. There is no evidence to date that this drug causes cancer in man when used in the dosages specified earlier. Follow your physician's instructions exactly. Avoid unnecessary or prolonged use.

Adverse Effects That May Mimic Natural Diseases or Disorders

Behavioral changes may suggest spontaneous psychosis.

Natural Diseases or Disorders That May Be Activated by This Drug

Latent yeast infections.

Possible Effects on Laboratory Tests

White blood cell counts: decreased. Prothrombin time: increased.

CAUTION

1. Troublesome and persistent diarrhea can develop in sensitive individuals. If diarrhea persists for more than 24 hours, discontinue this drug and consult with your physician.

2. Discontinue this drug immediately if you develop any indications of toxic effects on the brain or nervous system: confusion, irritability, dizziness, incoordination, unsteady stance or gait, muscle jerking or twitching, numbness or weakness in the extremities.

Precautions for Use

By Infants and Children: Avoid use in those with a history of bone marrow or blood cell disorders.

By Those over 60 Years of Age: Natural changes in the skin may predispose to yeast infections in the genital and anal regions. Report the develop­ment of rashes and itching promptly.

Advisability of Use During Pregnancy

Pregnancy Category: В (tentative). See Pregnancy Code inside back cover.

Animal studies: No birth defects reported in rat studies. However, this drug is known to cause cancer in mice and possibly in rats.

Human studies: No increase in birth defects reported in 206 exposures to this drug during the first 3 months. However, information from adequate studies of pregnant women is not available.

The manufacturer advises against the use of this drug during the first 3 months. Use during the last 6 months is not advised unless it is abso­lutely essential to the mother's health.

Advisability of Use if Breast-Feeding

Presence of this drug in breast milk: Yes. Avoid drug or refrain from nursing.

Habit-Forming Potential: None.

Effects of Overdosage: Weakness, stomach irritation, nausea, vomiting, confusion, disorientation.

Possible Effects of Long-Term Use: None reported. Avoid long-term use.

Suggested Periodic Examinations While Taking This Drug (at physician's discretion) Complete blood cell counts.

While Taking This Drug, Observe the Following

Foods: No restrictions.

Beverages: No restrictions. May be taken with milk.

Alcohol: Use caution until combined effects have been determined. A disul-firamlike reaction has been reported.

Tobacco Smoking: No interactions expected.

Other Drugs

Metronidazole may increase the effects of

• warfarin (Coumadin, etc.), and cause abnormal bleeding. The prothrombin time should be monitored closely, especially during the first 10 days of concurrent use.

Metronidazole taken concurrently with

• disulfiram (Antabuse) may cause severe emotional and behavioral disturbances.

Driving, Hazardous Activities: This drug may cause dizziness or incoordination. Restrict activities as necessary.

Aviation Note: The use of this drug may be a disqualification for piloting.

Consult a designated Aviation Medical Examiner.

TEXT 5. Read the following text and put questions to it.