Brand Name: Hycodan, Tussigon, Mycodone or Hydroment

Available in 5 mg tablets and oral syrup

Background

Narcotics have numerous therapeutic effects that are of interest clinically. Such effects include pain relief, anti-diarrheal effects, cardiovascular effects, and cough suppression. Hydrocodone is a narcotic developed to emphasize its cough suppression effect. It is somewhat more effective than codeine (another famous narcotic used in cough suppression) but possibly not as widely used in human medicine, at least not for this purpose.  

Hydrocodone suppresses cough directly by acting on the cough centers of the brain but it is also helpful in drying the respiratory secretions so that there is less material to cough up. This drying effect is further enhanced by the addition of homatropine, a second compound added to most hydrocodone products. While homatropine may enhance the drying of secretions, it is mainly added to reduce the abuse potential of hydrocodone. In the event of gross over-consumption, the homatropine will lead to unpleasant side effects, thus limiting the amount of hydrocodone that can be consumed.

How This Medication is Used

Some typical situations in which cough suppression with hydrocodone would be helpful include:

• Kennel cough (a usually minor infection leading to bronchitis).
• Collapsing trachea (where the windpipe becomes flimsy).
• "Old dog" bronchitis (a natural part of aging in dogs involves excess mucus production in the lungs).
• Heart enlargement (where the right chambers of the heart become so large that as the heart beats they pinch off the main airways).

These are all conditions where minor secretions or actual tissues are pressing on the lung's airways and stimulating cough. Coughs that benefit from suppression are typically dry and hacking, often described as sounding as though something is stuck in the throat.

In dogs, a dose of hydrocodone is believed to last approximately six to 12 hours. Hydrocodone is typically dosed four times a day or less, as needed.

Side Effects

The most common side effects of hydrocodone use include:

• Drowsiness or tranquilization
• Drying of respiratory secretions
• Constipation (if hydrocodone is given chronically)
• Upset stomach

Notify your veterinarian if any of these side effects appear to be causing your pet discomfort, but they are generally not considered serious.

Interactions with Other Drugs

This recommendation came about because serious side effects have been reported involving interactions between selegiline (treatment for "senility" in dogs) and mepiridine (more commonly known as demerol®, another narcotic). Based on this information, the recommendation to avoid the use of selegiline with ANY narcotic has been proposed at least until we know which narcotics are problematic in this situation. Because of this, dogs on selegiline should receive a different cough suppressant.  Similarly, hydrocodone should not be combined with amitraz-containing tick control products.

Mixing hydrocodone with other tranquilizers or with antihistamines increases the sedative side effects. (Note: there is a human product, brand name Tussionex®, which combines hydrocodone and the antihistamine chlorpheniramine. Clearly, there are many human respiratory infections for which an antihistamine and cough suppressant combination might be beneficial, but the sedation effects will be increased.)

A combination of hydrocodone and acepromazine, a tranquilizer, can not only lead to extreme sedation but can also lead to a serious drop in blood pressure.

If hydrocodone is combined with a tricyclic antidepressant or with a benzodiazepine tranquilizer, excessive sedation can result.

Some medications will not be as effective when combined with hydrocodone. These include diuretics and stomach prokinetic agents such as metoclopramide, cisapride, and clopidogrel (a blood thinner).

Concerns and Cautions

• Cough suppression is not appropriate in the event of pneumonia. In pneumonia, there is excessive pus and mucus accumulation in the lung, and this material must be coughed up. Suppressing the cough and drying the secretions will hinder the body's removal of this septic material.
• Narcotic cough suppressants should be avoided in cases involving obstructive diarrheas or toxic diarrheas (such as canine parvovirus infection). The narcotic will improve the intestinal tone, which will assist in absorbing water from the bowel and will improve stool consistency; however, it will also facilitate toxic absorption. In such situations, other forms of diarrhea treatment would be more appropriate.
• There are human formulations of hydrocodone that include acetaminophen. Acetaminophen has a narrow therapeutic range in dogs (meaning dosing must be very exact) and is not safe at any dose in cats. It is best not to attempt to use a hydrocodone preparation if it was not directly prescribed by your veterinarian for a specific patient.
• Opiates should be used with caution in patients with hypothyroidism, hypoadrenocorticism (Addison's disease), or debilitation from other diseases.
• If a dose is accidentally skipped, do not double up on the next dose. Simply give the medication when it is remembered or pick it up with the next dose, allowing at least the proper interval between doses according to the label instructions.
• Store at room temperature away from light.