Duloxetine, venlafaxine and desvenlafaxine are drugs with lots of potential to help people with pelvic pain.
These drugs are special because they have 2 different effects. They have SSRI and SNRI effects:
- the SNRI (serotonin norepinephrine reuptake inhibitor) effect treats pain. This increases the amount of norepinephrine effect in the brain.
- the SSRI (selective serotonin reuptake inhibitor) effect treats anxiety. This increases the amount of serotonin effect in the brain.
You may already be taking an SSRI medication for anxiety or low mood, but unless your medication is also an SNRI medication, it won’t be as effective for your pain.
Duloxetine, venlafaxine and desvenlafaxine have both SNRI and SSRI effects, so they help pain AND anxiety. If you aren’t anxious, that’s fine, they can still help pain.
Who might benefit from an SNRI medication?
SNRI medications help a mix of symptoms including:
– overall pain
– pelvic muscle pain
– anxiety or tension
– low mood
Like all medications, they don’t help everyone, but are worth considering if you have these conditions.
What are the side effects?
Common side effects can include nausea, loose bowels, and sometimes weight loss. As duloxetine tends to make you feel more awake, it is best taken in the morning.
In some people, but not all, there can be sexual dysfunction (lower libido and difficulty with orgasm).
If you have anxiety, then the medication might reduce this, but you may find your anxiety returns when you stop the medication. Some people with anxiety find it difficult to stop the medication for this reason.
These medications can interact with other medications you may be taking, so make sure you tell your doctor about all the medications you are taking (including herbal and over-the-counter medications) before you start them. When combined with other medications that affect serotonin, it is possible (but uncommon) to have a side effect called Serotonin Syndrome – so always check first with your doctor.
How to take duloxetine for pain
The normal dose for duloxetine is 30mg in the morning, increasing to 60 mg in the morning once any side effects have settled, possibly in a couple of weeks. However, if you are female, slim, or sensitive to medictions it is best to start these medications slowly. The smallest capsule has 30mg inside, so to reduce your starting dose you may wish to open the capsule, remove half the granules and throw them away. You can then close the capsule and take the capsule. This way you can start with a dose of 15mg rather than 30mg. Remember not to take the granules by themselves.
Some people find that duloxetine in the morning (when they want to be awake) and a small amount of amitriptyline (5-10mg) at night (when they want to sleep) is a good combination for pain. This combination has a very small chance of causing Serotonin Syndrome, but always discuss it with your doctor, and only start one medication at a time.
Serotonin Syndrome can occur when either the dose of a medication that affects Serotonin in the body is increased, or another medication that affects serotonin is added. It is rare when using either low dose amitriptyline or an SNRI – and still quite uncommon when these drugs are used together. However, adding a further medication that affects serotonin to the combination of amitriptyline (a tricyclic medication) and an SNRI medication makes Serotonin Syndrome more likely.
If you are on an SSRI or SNRI medication, always ask your doctor before starting a new medication. Medications that can affect Serotonin include:
- Other SSRI medications
- Bupropion – used for tobacco addiction
- Tricyclic antidepressants – such as amitriptyline and nortriptyline
- Monoamine oxidase inhibitors (MAOI’s) – an older type of anti-depressant rarely used now
- Anti-migraine treatments such as triptans, carbamazepine and valproic acid
- Tramadol – a pain medication
- Illicit drugs such as LSD, Ecstasy, cocaine and amphetamines
- Herbal supplements including St John’s Wort, ginseng and nutmeg
- Dextromethorphan – in some cough and cold medications
- Medications for nausea including metoclopramide, droperidol and ondansetron
- Linezolid – a rarely used antibiotic
- Rionavir – a medication for HIV/AIDS
Pregabalin, gabapentin, the contraceptive pill, codeine and anti-inflammatory medications do not affect Serotonin, so do not interact with these medications.
What are the symptoms of Serotonin Syndrome?
Symptoms of serotonin syndrome can include:
- agitation, confusion, headache
- shivering, sweathing, diarrhoea, high BP, rapid HR
- muscle rigidity, twitching, dilated pupils
If you believe you may have symptoms of Serotonin Syndrome, always contact your doctor. Stopping or reducing the medications involved may be all that is required. Severe cases may require admission to hospital.