التداخل الدوائي مهم.

It is understandable in Egypt, but it sounds formal and medical, so it is closer to Modern Standard Arabic than casual everyday Egyptian.

An Egyptian doctor, pharmacist, or medical text could definitely use it. In more everyday speech, people might also say things like:

• تفاعل الأدوية مهم
• التداخل بين الأدوية مهم

So yes, it works in Egypt, but it is not especially colloquial.

Arabic often leaves out the present-tense verb to be.

So:

• التداخل الدوائي = the drug interaction / drug-related interaction
• مهم = important

Together, التداخل الدوائي مهم literally looks like the drug interaction important, but it means The drug interaction is important.

This is very normal in Arabic, including Egyptian.

Because in this kind of Arabic sentence, you usually get:

• noun phrase first
• description/comment second

So:

• التداخل الدوائي = the subject/topic
• مهم = what is being said about it

This is the normal order for a simple sentence like X is important.

In Arabic, adjectives normally come after the noun they describe.

So:

• التداخل الدوائي = literally the interaction the-drug-related
• natural English meaning = the drug interaction or the drug-related interaction

That is standard Arabic word order:

• noun first
• adjective second

Arabic often uses ال with general concepts in places where English does not use the.

So Arabic may say something that is literally the drug interaction, but in English the best translation can still be simply drug interaction or drug interactions, depending on context.

This is common with general statements and abstract ideas. So the Arabic definite article does not always match English the one-for-one.

Because Arabic adjectives usually match the noun they describe in definiteness.

Here:

• التداخل is definite because it has ال
• so the adjective الدوائي also becomes definite

That is why you get:

• التداخل الدوائي

not:

• التداخل دوائي

So the pattern is:

• definite noun + definite adjective
• indefinite noun + indefinite adjective

الدوائي means something like:

• drug-related
• medicinal
• pharmaceutical

It comes from دواء, meaning medicine or drug.

So التداخل الدوائي is not just any kind of interaction. It is specifically a drug-related interaction, usually what English calls a drug interaction.

Because the thing being described is التداخل, and التداخل is grammatically masculine.

So the adjective must match it:

• masculine: مهم
• feminine: مهمة

Since التداخل is masculine, مهم is correct.

A good Egyptian-style pronunciation is:

et-tadākhul ed-dawāʔi

A few important points:

• the written ال is often pronounced more like el- in Egyptian
• but with certain letters, the l sound disappears and the next consonant doubles
• ت and د are both among those letters

So:

• التداخل is pronounced roughly et-tadākhul, not el-tadākhul
• الدوائي is pronounced roughly ed-dawāʔi, not el-dawāʔi

This happens because ت and د are sun letters.

That is the hamza: ء.

In دوائي, it gives a small break or catch in the voice:

• dawāʔi

So you do not say it as one fully smooth stretch like dawaai. There is a slight stop before the last vowel.

This comes from the base word دواء.

Often, yes. In everyday Egyptian, especially outside formal medical contexts, people may choose simpler or more conversational wording.

Possible alternatives include:

• تفاعل الأدوية مهم
• التداخل بين الأدوية مهم

These can sound more natural in speech, depending on the exact context.

So التداخل الدوائي مهم is correct and useful, especially in formal or medical Arabic, but it is not the only way an Egyptian might express the idea.

Because in normal writing, especially in Egyptian and everyday use, case endings are usually not written and not pronounced.

In very formal fully vowelled Standard Arabic, you might see extra endings, but in ordinary Arabic text you usually just see:

• التداخل الدوائي مهم

without those grammatical endings.

So what you see here is the normal practical way Arabic is written.