From the Guidelines
Mixing Ativan (lorazepam) and Benadryl (diphenhydramine) is generally not recommended without medical supervision due to potentially dangerous additive effects. Both medications are central nervous system depressants that can cause increased sedation, drowsiness, dizziness, confusion, and impaired coordination when taken together. This combination may also lead to respiratory depression in some individuals, particularly the elderly or those with underlying respiratory conditions. The most recent and highest quality study, 1, provides information on the use of lorazepam and diphenhydramine, highlighting their potential for increased sedation and anticholinergic effects when used together. If you're considering taking these medications together, consult with your healthcare provider first. They may recommend adjusting dosages, timing the medications differently, or suggesting alternative treatments. In emergency situations where both medications have been prescribed, ensure you follow exact dosing instructions and avoid activities requiring mental alertness such as driving. The interaction occurs because both drugs affect similar neurotransmitter systems in the brain - Ativan enhances the effects of GABA while Benadryl blocks histamine and has anticholinergic properties, creating a potentially dangerous synergistic sedative effect. Some key points to consider when taking these medications together include:
- Increased risk of respiratory depression, particularly in the elderly or those with underlying respiratory conditions
- Potential for increased sedation, drowsiness, dizziness, confusion, and impaired coordination
- Anticholinergic effects, such as dry mouth, blurred vision, and constipation, may be increased when taking diphenhydramine with lorazepam
- The combination of these medications may lead to paradoxical excitement, especially in children and adolescents
- It is essential to follow the exact dosing instructions and to avoid activities that require mental alertness, such as driving or operating heavy machinery.
From the Research
Mixing Lorazepam and Diphenhydramine
- There is evidence to suggest that lorazepam and diphenhydramine can be mixed, as seen in the study 2 which compared the effects of lorazepam plus diphenhydramine (Somnium) versus lorazepam alone in patients with non-organic insomnia related to mild generalized anxiety disorder.
- The study 2 found that the combination of lorazepam and diphenhydramine showed synergistic effects in hypnotic properties and antagonistic effects in regard to toxicity, and was well tolerated with no significant adverse effects.
- However, it is essential to note that the study 2 was conducted in a specific patient population and under controlled conditions, and the results may not be generalizable to all individuals or situations.
- Additionally, other studies 3, 4, 5, 6 do not provide direct evidence on the safety and efficacy of mixing lorazepam and diphenhydramine, but highlight the importance of caution when co-prescribing sedating agents due to the risk of respiratory depression and other adverse effects.
Safety Considerations
- The study 3 found that concomitant use of sedating antipsychotics and prescription opioids was associated with an increased risk of overdose, emphasizing the need for caution when co-prescribing sedating agents.
- The study 4 noted that haloperidol, a typical antipsychotic, can be associated with extrapyramidal symptoms, which can be controlled by co-administration of promethazine, an antihistamine.
- The study 6 found that lorazepam caused no significant hypoxemia and had a shorter duration of action than diazepam in patients with chronic obstructive lung disease, but emphasized the need for caution when using tranquillisers in such patients.