Nocturia

High urine output at night is by far the most common cause of frequent urination at night (80%).

An important function of the bladder is to wake you up when it is full (i.e. has reached it's capacity). This is a learned behavior which is typically taught during toilet training. If people did not awaken when the bladder was full, then they would wet the bed. Bedwetting in adulthood is considered abnormal and is known as 'enuresis'. 

The bladder is doing it's job if it wakes you when it is full. It is easy to determine if high output of urine at night (also known as nocturnal polyuria) is a contributing factor by doing a voiding diary. Normal bladder capacity tends to decrease with age, but is usually in the 250-500 cc range (about 10-15 ounces). If your voiding diary shows that your night time voided volumes are in this range, the problem is not with the bladder.

The amount of urine which is produced at night is dependent on many factors, but most importantly:

1. Fluid intake: the amount, type and timing are important: everything that you drink must come out at some point. Fluids consumed within a few hours of bed time will usually enter the bladder in a few hours. If the bladder becomes full, it should wake you up. Caffeine and alcohol are diuretics and can increase night time urine production and should be avoided.

2. Fluid redistribution: this includes retention of fluid during the day with preferential urine formation during the night. Fluid accumulation earlier in the day - frequently in the legs - is common with congestive heart failure and venous insufficiency. Once asleep and in the horizontal position, the fluid is reabsorbed and increased urine output is the result. Diuretics and blood-pressure lowering pills may also cause increased urine output if they are taken close to bed time.

3. Hormonal changes: vasopressin is a hormone released by the heart, mainly at night. One function is to temporarily reduce urine output during sleep. If secretion of vasopression is impaired, which is common with age, then increased urine output will ensue.

Most people assume that a problem with the lower urinary tract (the bladder and urethra - the prostate being part of the urethra in males) is the most common cause. This is incorrect as high urine output is the most common cause by far.

Having said that, lower urinary tract dysfunction may be causative in some people.

There are 3 basic mechanisms of nocturia related to bladder function:

1. Small bladder capacity: this is actually quite an uncommon cause.

2. Bladder spasticity: the bladder contracts when it should be 'quiet'

3. Abnormal bladder sensitivity: the bladder sends a signal that it is full, even when it has not reached capacity

There are a large number of causes including BPH, OAB, neurologic dysfunction, infections, etc.

Often times, people will go to the washroom simply because they have awoken for other reasons. The do not specifically wake to urinate but happen to do so out of habit.

Insomnia occurs has many causes including poor sleep hygiene and sleep apnea.

These steps should always be tried but may not be successful.

• Optimizing sleep hygiene. Avoid afternoon naps, be active with a walk in the evening, keep electronic devices out of bed, optimizing temperature (with a hot water bottle if cold or using thinner blankets if hot), having a routine time to go to bed and wake.

• Using low dose melatonin (1-2 mg nightly) may improve sleep.

• Minimizing fluid retention and urine production. Avoidance of increased fluid intake for 3-4 hours before bed. Avoiding drinking at night when waking to urinate (this will only make the problem worse).

• Avoid caffeine and alcohol in the evening.

• Reduce salt intake.

• Elevation of legs before bed or compression stockings if leg swelling is present.

Adjusting the timing of when a patient takes specific medications can have a large impact on when and how much urine is produced.

Short acting diuretics such as hydrochlorothiazide or furosemide should be taken in the early afternoon. This will ensure that the body is ‘maximally dry’ just before bed so that the amount of urine being produced at night is minimized.

Conversely, adding a short acting diuretic in cases where daytime fluid retention is present may be helpful. Hydrochlorothiazide 25 mg or furosemide 20 mg may help.

These medications are the mainstay of treatment when behavioral modification is ineffective.

See below.

Well timed diuretics can ‘dry out’ the body prior to sleep and reduce urine output. They should be taken in the afternoon.

• Hydrochlorothiazide 25 mg daily.

• Furosemide (Lasix) 20-40 mg daily

Unless nocturia in a man is the result of incomplete emptying, these medications are usually not helpful. See the section on BPH management.

Only helpful if OAB is present. In OAB, the urinary frequency and urgency are typically present during the day but often absent at night. Oral antispasmodics and Botox may have a limited role. See the section on OAB.

Oxybutyinin 5 mg nightly has a short duration of action and may provide targeted treatment of OAB symptoms at night.

Vaginal estrogen can be very effective in treating nocturia in post-menopausal women who have syndrome of urogenital atrophy.

Desmopressin (DDAVP) is a synthetic medication closed related to vasopressin (aka anti-diuretic hormone or ADH). It retains the anti-diuretic effects of vasopressin but does not cause hypertension. It is marketed under different names (see below) and is available by mouth or by nose spray.

There are several different formulations which differ markedly in dosing because the nasal and oral disintegrating tablets (ODT, ‘sublingual’) are absorbed 20x better than the usual oral tablets

• Intranasal spray: 10 mcg/spray; max. 40 mcg/day. Trade names: Stimate, Minirin, Noctiva.

• DDAVP Tablets (Oral tablets NON dissolving): 0.1 mg tablets; maximum 0.6 mg per day. Most men require 0.4 mg daily with starting dose 0.1 mg increased weekly in 0.1 mg increments.

• Oral/sublingual dissolving tablets (ODT):

  • DDAVP MELT: 60, 120, 240 mcg tablets.

  • DDAVP MELT low dose (Nocdurna): 27.5 mcg (women; equivalent to 25 mcg of desmopressin) and 55.3 mcg (men; equivalent to 50 mcg desmopressin).

DDAVP is short for ‘Deamino D-arginine vasopressin’.

Some patients should avoid desmopressin because these medications can cause electrolyte disturbance and fluid retention. DDAVP should be avoided or used with caution when any of the following conditions are present.

• Congestive heart failure.

• Peripheral edema.

• Polydipsia (inability to comply with instructions to reduce fluid intake).

• Renal failure .

• Uncontrolled high blood pressure.

• Low sodium levels.

Monitoring for side-effects is very important since electrolyte imbalance and fluid overload may occur. Low sodium (hyponatremia) occurs in about 1 in 30 patients and may cause serious complications.

Monitoring is the same for all the different types of medications in this class.

1. STOP the medication if you experience any of the following: lightheadedness, nausea, vomiting, headache or new problems with your vision.

2. Weigh yourself before starting the medication then daily for the first week after starting the medication. Weigh yourself every 1-2 weeks thereafter. STOP the medication if you notice that your legs are swelling or you put on more than a couple of pounds.

3. DO THE RECOMMENED LAB TESTING. Checking for low sodium and kidney disfunction is important. Do the lab testing:

   1. 2-3 days after starting treatment.

   2. 2-3 weeks after starting treatment

   3. Every few months thereafter.

1. Restrict fluids for 1 hour prior and 8 hours after taking the medication.

2. Dose titration. A low dose will usually be prescribed at the start. The dose will be increased as needed. Do not increase the dose on your own without discussing with your physician.

3. Ensure you follow the instructions for monitoring.