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 this medicine, the following should be considered:
Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Pediatric

No information is available on the relationship of age to the effects of famciclovir in children under 18 years of age. Safety and efficacy have not been established.
Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of famciclovir in the elderly. However, elderly patients are more likely to have age-related kidney disease, which may require an adjustment of dose in patients receiving this medicine.
Pregnancy Pregnancy Category Explanation
All Trimesters B Animal studies have revealed no evidence of harm to the fetus, however, there are no adequate studies in pregnant women OR animal studies have shown an adverse effect, but adequate studies in pregnant women have failed to demonstrate a risk to the fetus.

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with 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. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Galactose intolerance or
• Glucose-galactose malabsorption or
• Severe lactase deficiency—Should not use in patients with these conditions.
• Kidney disease—Use with caution.

The effects may be increased because of slower removal of the medicine from the body.

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:

• Incidence not known 

Black, tarry stools
bleeding gums
blistering, peeling, or loosening of the skin
blood in urine or stools
chills
clay-colored stools
cough
dark urine
dizziness
fever
joint or muscle pain
loss of appetite
pinpoint red spots on the skin
red, irritated eyes
sore throat
sores, ulcers, or white spots in the mouth or on the lips
unpleasant breath odor
unusual bleeding or bruising
vomiting of blood
yellow eyes or skin

Some 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. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

• More common 

Cramps
diarrhea
headache
heavy bleeding
nausea
stomach pain

• Less common 

Bloated, full feeling
burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feeling
confusion as to time, place, or person
excess air or gas in the stomach or intestines
hives or welts
holding false beliefs that cannot be changed by fact
itching skin
mood or mental changes
passing gas
rash
redness of skin
seeing, hearing, or feeling things that are not there
unusual excitement, nervousness, or restlessness
unusual tiredness or weakness
vomiting

• Incidence not known 

Sleepiness or unusual drowsiness

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