In the U.S.—

In Canada—

Another commonly used name is ddC.

• Antiviral, systemic

Zalcitabine (zal-SITE-a-been) (also known as ddC) is used in the treatment of the infection caused by the human immunodeficiency virus (HIV). HIV is the virus that causes acquired immune deficiency syndrome (AIDS).

Zalcitabine (ddC) will not cure or prevent HIV infection or AIDS; however, it helps keep HIV from reproducing and appears to slow down the destruction of the immune system. This may help delay the development of problems usually related to AIDS or HIV disease. Zalcitabine will not keep you from spreading HIV to other people. People who receive this medicine may continue to have other problems usually related to AIDS or HIV disease.

Zalcitabine may cause some serious side effects, including peripheral neuropathy (a problem involving the nerves). Symptoms of peripheral neuropathy include tingling, burning, numbness, or pain in the hands or feet. Zalcitabine may also cause pancreatitis (inflammation of the pancreas). Symptoms of pancreatitis include stomach pain, and nausea and vomiting. Check with your doctor if any new health problems or symptoms occur while you are taking zalcitabine.

Zalcitabine is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S. and Canada)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For zalcitabine, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to zalcitabine. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Zalcitabine has not been studied in pregnant women. However, studies in animals have shown that zalcitabine causes birth defects when given in very high doses. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding—It is not known whether zalcitabine passes into the breast milk. However, if your baby does not already have the AIDS virus, there is a chance that you could pass it to your baby by breast-feeding. Talk to your doctor first if you are thinking about breast-feeding your baby.

Children—Zalcitabine can cause serious side effects in any patient. Therefore, it is especially important that you discuss with your child's doctor the good that this medicine may do as well as the risks of using it. Your child must be seen frequently and your child's progress carefully followed by the doctor while the child is taking zalcitabine.

Older adults—Zalcitabine has not been studied specifically in older people. Therefore, it is not known whether it causes different side effects or problems in the elderly than it does in younger adults.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking zalcitabine, it is especially important that your health care professional know if you are taking any of the following:

• Alcohol or
• Asparaginase (e.g., Elspar) or
• Azathioprine (e.g., Imuran) or
• Estrogens (female hormones) or
• Furosemide (e.g., Lasix) or
• Methyldopa (e.g., Aldomet) or
• Pentamidine by injection (e.g., Pentam, Pentacarinat) or
• Sulfonamides (e.g., Bactrim, Septra) or
• Sulindac (e.g., Clinoril) or
• Tetracyclines or
• Thiazide diuretics (water pills) (e.g., Diuril, Hydrodiuril) or
• Valproic acid (e.g., Depakote)—Use of these medicines with zalcitabine may increase the chance of pancreatitis (inflammation of the pancreas)

• Aminoglycosides by injection (amikacin [e.g., Amikin], gentamicin [e.g., Garamycin], kanamycin [e.g., Kantrex], neomycin [e.g., Mycifradin], netilmicin [e.g., Netromycin], streptomycin, tobramycin [e.g., Nebcin]) or
• Amphotericin B (e.g., Fungizone) or
• Foscarnet (e.g., Foscavir)—Use of these medicines with zalcitabine may increase the chance of side effects

• Antacids, aluminum- and/or magnesium-containing (e.g., Maalox, Mylanta)—Use of antacids with zalcitabine may decrease the absorption of zalcitabine; antacids and zalcitabine should not be taken at the same time

• Chloramphenicol (e.g., Chloromycetin) or
• Cisplatin (e.g., Platinol) or
• Dapsone (e.g., Avlosulfon) or
• Didanosine (e.g., Videx, ddI) or
• Disulfiram (e.g., Antabuse) or
• Ethionamide (e.g., Trecator-SC) or
• Glutethimide or
• Gold (arthritis medicine) or
• Hydralazine (e.g., Apresoline) or
• Iodoquinol (e.g., Dinquinol, Yodoxin) or
• Isoniazid (e.g., Nydrazid) or
• Metronidazole (e.g., Flagyl) or
• Phenytoin (e.g., Dilantin) or
• Ribavirin (e.g., Virazole) or
• Stavudine (e.g., Zerit, d4T) or
• Vincristine (e.g., Oncovin)—Use of these medicines with zalcitabine may increase the chance of peripheral neuropathy (tingling, burning, numbness, or pain in your hands or feet)

• Cimetidine (e.g., Tagamet) or
• Probenecid (e.g., Benemid)—Use of these medicines with zalcitabine may increase the chance of side effects of zalcitabine

• Doxorubicin (e.g., Adriamycin or Rubex) or
• Lamivudine (e.g., 3TC, Epivir, Heptovir)—Use of these medicines with zalcitabine may make zalcitabine not work well

• Nitrofurantoin (e.g., Furadantin, Macrodantin)—Use of nitrofurantoin with zalcitabine may increase the chance of side effects, including peripheral neuropathy (tingling, burning, numbness, or pain in your hands or feet) and pancreatitis (inflammation of the pancreas)

• Alcohol abuse or
• Increased amylase (or a history of ) or
• Increased blood triglycerides (or a history of) or
• Pancreatitis (or a history of, or at risk for)
• Receiving nutrition in your veins—Patients with these medical problems may be at increased risk of pancreatitis (inflammation of the pancreas)

• Abnormal liver function, or
• Alcohol abuse, history of, or
• At risk for liver disease, or
• Hepatitis, or
• Liver disease, or
• Obesity, or
• Taking medicines called nucleosides for a long time—Zalcitabine may make liver disease worse in patients with liver disease or a history of alcohol abuse

• Allergy to zalcitabine, or
• Allergy to any part of the medicine—Serious allergic reactions can occur

• Bone marrow disease—Patients with this condition may develop severe blood problems when taking zalcitabine

• Heart problems, or
• Congestive heart failure—Zalcitabine may make these conditions worse.

• Kidney disease—Patients with kidney disease may have an increased chance of side effects

• Low CD4 cell count—Zalcitabine may cause serious side effects in patients with very low CD4 cell counts.

• Peripheral neuropathy or at risk of developing peripheral neuropathy, or
• Diabetes, or
• Low CD4 cell count, or
• Weight loss—Zalcitabine may increase your chance of developing neuropathy or worsening neuropathy.

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. Also, do not stop taking this medicine without checking with your doctor first.

Keep taking zalcitabine for the full time of treatment , even if you begin to feel better.

This medicine works best when there is a constant amount in the blood. To help keep the amount constant, do not miss any doses . If you need help in planning the best times to take your medicine, check with your health care professional.

Only take medicine that your doctor has prescribed specifically for you. Do not share your medicine with others.

Dosing—

The dose of zalcitabine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of zalcitabine. Your dose may be different if you have kidney disease. If your dose is different, do not change it unless your doctor tells you to do so:

• For oral dosage form (tablets):
  • For treatment of HIV infection:
    • Adults and children 12 years of age and older—0.75 milligrams (mg)
    • Children up to 12 years of age—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

It is very important that your doctor check your progress at regular visits.

Do not take any other medicines without checking with your doctor first. To do so may increase the chance of side effects from zalcitabine.

HIV may be acquired from or spread to other people through infected body fluids, including blood, vaginal fluid, or semen. If you are infected, it is best to avoid any sexual activity involving an exchange of body fluids with other people. If you do have sex, always wear (or have your partner wear) a condom (“rubber”). Only use condoms made of latex, and use them every time you have vaginal, anal, or oral sex. The use of a spermicide (such as nonoxynol-9) may also help prevent transmission of HIV if it is not irritating to the vagina, rectum, or mouth. Spermicides have been shown to kill HIV in lab tests. Do not use oil-based jelly, cold cream, baby oil, or shortening as a lubricant—these products can cause the condom to break. Lubricants without oil, such as K-Y Jelly, are recommended. Women may wish to carry their own condoms. Birth control pills and diaphragms will help protect against pregnancy, but they will not prevent someone from giving or getting the AIDS virus. If you inject drugs , get help to stop. Do not share needles or equipment with anyone. In some cities, more than half of the drug users are infected, and sharing even 1 needle or syringe can spread the virus. If you have any questions about this, check with your health care professional.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• More common
  • Lab results that show problems with liver;  tingling, burning, numbness, or pain in the hands, arms, feet, or legs 
  
  

• Less common
  • Fever;  joint pain;  muscle pain;  nausea and vomiting;  seizures;  skin rash;  stomach pain (severe);  ulcers in the mouth and throat 
  
  

• Rare
  • Discouragement, feeling sad or empty, irritability, lack of appetite, loss of interest or pleasure, tiredness, trouble concentrating, trouble sleeping ;  fever and sore throat;  yellow eyes or skin 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• Less common
  • Constipation;  diarrhea;  headache;  hives or welts;  itching skin;  swelling or inflammation of the mouth 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.