Rimantadine Dosage

Usual Adult Dose for Influenza A

Normally recommended dose: 100 mg orally twice a day for 7 days

Usual Adult Dose for Influenza Prophylaxis

Normally recommended dose: 100 mg orally twice a day

Usual Geriatric Dose for Influenza Prophylaxis

Elderly nursing home patients and patients over the age of 65 years: A dose reduction to 100 mg orally once a day is normally recommended.

Usual Geriatric Dose for Influenza A

Elderly nursing home patients and patients over the age of 65 years: A dose reduction to 100 mg orally once a day is normally recommended.

Usual Pediatric Dose for Influenza A

Normally recommended dose:
17 years or older: 100 mg orally twice a day for 7 days

Usual Pediatric Dose for Influenza Prophylaxis

Normally recommended dose:
1 to 9 years: 5 mg/kg (up to 150 mg) orally once a day
10 years or older: 100 mg orally twice a day

Renal Dose Adjustments

Severe renal impairment (CrCl 5 to 29 mL/min) or renal failure (CrCl 10 mL/min or less): A dose reduction to 100 mg orally once a day is normally recommended.

Liver Dose Adjustments

Severe hepatic dysfunction: A dose reduction to 100 mg orally once a day is normally recommended.

Dose Adjustments

Some clinicians recommend 200 mg orally once a day for the treatment or prevention of seasonal influenza A virus infection in adults.

Precautions

On the basis of available antiviral testing results, the US Public Health Service Centers for Disease Control and Prevention (CDC) has provided an interim recommendation that rimantadine not be used for the treatment or prophylaxis of influenza in the United States for the remainder of the 2010 through 2011 influenza season. During this period, oseltamivir or zanamivir should be selected if an antiviral medication is used for the treatment or prophylaxis of influenza.

Rimantadine should be used with caution in patients with a history of seizures. It has been associated with an increased incidence of seizure-like activity in patients with a history of seizures who were not taking anticonvulsants during rimantadine therapy. Rimantadine should be discontinued if seizures occur.

Due to the potential for accumulation of rimantadine metabolites during multiple dosing, caution is recommended when patients with renal or hepatic insufficiency are treated with rimantadine. Such patients should be monitored for side effects.

Rimantadine given concurrently with intranasal live attenuated influenza vaccine (LAIV) has not been studied. Due to the possible interference, LAIV should not be used within 2 weeks prior to or 48 hours following rimantadine use.

Influenza viruses change over time and the emergence of resistant or more virulent mutations may decrease the efficacy of rimantadine. The available influenza drug susceptibility patterns and treatment effects should be considered when deciding whether to use rimantadine.

Safety and efficacy of rimantadine prophylaxis have not been established for longer than 6 weeks.

Safety and efficacy for prophylaxis of influenza have not been established in pediatric patients less than 1 year of age. Safety and efficacy in the treatment of influenza have not been established in pediatric patients less than 17 years of age.

Dialysis

Severe renal impairment (CrCl 5 to 29 mL/min) or renal failure (CrCl 10 mL/min or less): A dose reduction to 100 mg orally once a day is normally recommended.

Rimantadine is not removed by hemodialysis.

Other Comments

Therapy should begin within 48 hours of the onset of signs and symptoms of influenza A infection. The efficacy of rimantadine started after 48 hours is not known. Therapy should be continued for about 7 days from the initial onset of symptoms.

Prophylaxis is generally started when an outbreak of Influenza A is documented and continued until it is over, if necessary, or until an immune response is provided by immunization (2 to 4 weeks after vaccination).

Annual vaccination is the preferred method for prophylaxis against influenza A and rimantadine should not be considered a substitute.

Compounded rimantadine oral suspension is preferred for patients who have difficulty swallowing tablets.

During emergency situations only:
For patients who have difficulty swallowing tablets or where lower doses are needed, an oral suspension (10 mg/mL) may be prepared from rimantadine 100 mg tablets using Ora-Sweet (R) as follows:

1. After verifying the prescribed dose is correct, calculate the mg amount of rimantadine needed for the duration of therapy.
(daily dose) x (number of days) = (mg of rimantadine)

2. Round up the mg of rimantadine amount to the next 100 mg designation.

3. Determine the number of rimantadine 100 mg tablets necessary for the compounded oral suspension.
(rounded mg of rimantadine) divided by (100 mg/tablet) = (number of tablets)

4. Determine the total volume of compounded oral suspension (10 mg/mL).
(rounded mg of rimantadine) divided by (10 mg/mL) = (total volume)

5. Before beginning to compound the oral suspension, the calculations should be verified. Use the following procedure to compound the oral suspension (10 mg/mL) from rimantadine 75 mg tablets:
(a) Place the required number of rimantadine 100 mg tablets into a clean mortar of sufficient size to hold the tablets and volume of vehicle, Ora-Sweet (R) used in Step (c).
(b) Grind the tablets and triturate to a fine powder with a pestle. Powder on the sides of the mortar or pestle should be removed with a spatula and incorporated into the trituration throughout the process.
(c) Slowly add about one-third (1/3) of the total volume of vehicle to the mortar while triturating until a uniform suspension is achieved.
(d) Transfer the suspension to an amber glass or PET plastic bottle. To eliminate spillage, a funnel may be used.
(e) Slowly add the second one-third (1/3) of the total volume of vehicle to the mortar, rinse the mortar and pestle by a triturating motion, and transfer the contents into the bottle.
(f) Repeat the rinsing with the remaining one-third (1/3) of the vehicle, transferring the remaining contents to the fullest extent possible. Verify the suspension is at the desired total volume or add additional vehicle if needed.
(g) Use a child-resistant cap to close the bottle.
(h) Shake well to ensure homogeneous suspension. The active drug, rimantadine HCl, is soluble in the specified vehicle but some of the inert ingredients are insoluble, causing the suspension.

To minimize the entrapment of air, the compounded oral suspension should be shaken gently before each use. Any remaining suspension must be discarded following completion of therapy or after the labeled expiration date. The compounded oral suspension is stable for 14 days at room temperature; therefore, the maximum amount to be dispensed should not exceed a 14 day supply.

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