In a nutshell

Prescription medication can affect your memory. This can either be because of a particular drug, or because of the interaction of that drug with another one. If you’ve started experiencing memory loss, it’s worth checking the list below to see if the medication you are taking could be the reason behind it.
BUT REMEMBER! Never stop taking any drugs without the full knowledge and guidance of your doctor. If you’re concerned about your memory loss, find out if there are alternative drugs or treatment options that can replace them.

Cholesterol-lowering drugs

People take cholesterol-lowering drugs (statins) because high levels of cholesterol can lead to a hardening of the arteries in the body, which can increase the risk of heart disease.
However, while statins reduce levels of bad cholesterol in the blood, they can also reduce levels in the brain, which are needed for the formation of connections between nerve cells.

Antianxiety drugs

These are drugs used to treat different types of anxiety including agitation, delirium and muscle spasms. They are sometimes used to treat insomnia and depression.
Antianxiety drugs (Benzodiasepines) dampen activity in certain areas of the brain related to the transfer of short-term to long-term memories.

Narcotic painkillers

People who suffer from moderate to severe pain may be prescribed what are sometimes known as opioid analgesics. This may be the case, for example, if you suffer from a condition such as rheumatoid arthritis.
Narcotic painkillers can affect memory because they stem pain signals by affecting chemical messengers in the brain. However, the knock on effect is that they also interfere with chemical messengers involved in long and short-term memory.

Antiseizure drugs

These are prescribed to people to prevent seizures, but can sometimes be given for nerve pain, bipolar disorders and mood disorders.
They work by dampening signals within the central nervous systems that can cause seizures. However, they also dampen the signals linked to memory.

Antidepressant drugs

These drugs (tricyclic antidepressants) are prescribed for people who are not only depressed, but also suffer anxiety, eating disorders, obsessive-compulsive disorder, chronic pain and some hormone related problems such as menstrual cramps and post-menopausal hot flushes.
Around 35 per cent of people who take tricyclic antidepressants report some memory problems, and 54 per cent have difficulty concentrating. This is because the drugs block the action of a chemical brain messenger called serotonin.

Parkinson’s disease drugs

Designed to activate the signalling pathways for dopamine, a chemical brain messenger which aids fine motor control, occasionally Parkinson's disease drugs (Dopamine agonists) can cause side effects such as confusion, memory loss, delusions and drowsiness. These drugs are sometimes prescribed to people with restless legs syndrome.

Incontinence drugs

These medications are used to treat people with an overactive bladder or urge incontinence (where you get a sudden urge to urinate and can’t get to the bathroom in time).
They work by blocking the action of a chemical in the brain called acetylcholine, which is responsible for various functions within the body. Anticholinergics (which are what incontinence drugs are known as), prevent the involuntary contraction of muscles involved in urinating.
Unfortunately, acetylcholine is a key chemical needed for helping with the processing of memories, so if it’s blocked, you can end up with memory loss. It also goes some way to explaining why people with dementia, who are often deficient in acetylcholine, can end up being affected by incontinence problems.

High blood pressure drugs

People with high blood pressure are often prescribed beta-blockers to slow the heart rate and lower blood pressure. They can sometimes be given to people with angina (chest pains), abnormal heart rhythms, migraines and certain types of glaucoma (an eye condition).
Beta-blockers work by blocking chemical messengers in the brain, including norepinephrine and epinephrine. However, this also affects the formation of memories.

Sleeping pills

People suffering from insomnia and other serious sleep problems can be prescribed drugs to aid sleep. They’re sometimes known as ‘Z’ drugs because many of the names either begin with or have the letter ‘z’ in them. For example, eszopiclone, zaleplon and zolpidem. They are collectively known as nonbenzodiazepine sedative hypnotics.
They’re similar to antianxiety drugs in the way they act upon chemical messengers in the brain and produce a similar effect. Sleeping pills can be addictive and can cause amnesia, so if you’ve noticed your memory problems worsening since you started taking them, speak to your doctor about gradually reducing your dose.

Antihistamines

These drugs are used to relieve symptoms of allergy to pollens, animal hair and food. They can be prescription or over-the-counter and they work by inhibiting acetylcholine (much like incontinence drugs). This chemical messenger is not only responsible for body functions, but also creates memories in the brain.
The good news is that these side effects are limited to certain antihistamines (often dubbed ‘first generation’). There are still other types that do NOT cause memory loss. The following drugs have an increased risk of causing memory loss: Benadryl (diphenhydramine) and Piriton (chlorphenamine).
However, ‘new generation’ antihistamines such as Clarityn (Loratadine) and Zyrtec (Cetirizine) or any versions that are marketed as non-drowsy don’t produce the same impaired thinking and memory problems.