الاثار الجانبية فيها نعاس.

A common Egyptian-style pronunciation would be:

el-āsār el-gānibeyya fīhā noʿās

A few useful notes:

• ال is often pronounced el- in Egyptian, not al-.
• ج in الجانبية is a hard g in Egyptian, like go.
• ث in آثار is often pronounced like s in everyday Egyptian, so you may hear āsār rather than āthār.
• ع in نعاس is the deep Arabic sound ʿ. If that sound is still hard for you, that is normal.

Here is the breakdown:

• الآثار = the effects
• الجانبية = side / secondary
• الآثار الجانبية = the side effects
• فيها = in it / in them, and here more naturally it has or they include
• نعاس = drowsiness / sleepiness

So the structure is basically:

the side effects + include/have + drowsiness

Because Arabic often leaves out the verb to be in the present tense.

So instead of saying something like The side effects are... or The side effects have..., Arabic can simply say:

الآثار الجانبية فيها نعاس

Literally, it is something like:

the side effects — in them drowsiness

But in natural English, that becomes the side effects include drowsiness or the side effects cause drowsiness.

Literally, فيها is:

• في = in
• ها = it / her

So literally it means in it.

But in sentences like this, it often has the more natural English meaning of:

• has
• contains
• includes
• there is ... in it

So فيها نعاس is literally there is drowsiness in it, but more naturally in English: it includes drowsiness.

This is a very common Arabic pattern.

Non-human plural nouns are often treated grammatically like feminine singular.

Since الآثار is a non-human plural, Arabic commonly refers back to it with ها, not هم.

So:

• الآثار الجانبية فيها نعاس = correct and natural
• فيهم would sound wrong here

This same rule appears a lot in Arabic, especially with objects, ideas, and abstract things.

For the same reason: non-human plural nouns often take a feminine singular adjective.

So:

• الآثار = plural
• الجانبية = feminine singular adjective

That is normal Arabic agreement for non-human plurals.

This is sometimes called deflected agreement.
It is one of those patterns that feels strange to English speakers at first, but it is very common.

Because نعاس here is an indefinite noun used as part of the predicate.

That is very normal in Arabic after expressions like فيه / فيها.

Compare:

• فيه صداع = there is a headache / there is headache
• فيه ألم = there is pain
• فيها نعاس = there is drowsiness

Using النعاس would usually sound more specific, like a particular known drowsiness already being talked about.

It is understandable in Egyptian Arabic, but it sounds a bit formal or medical.

Why?

• الآثار الجانبية is a formal expression, common in medical or written language
• فيها نعاس is perfectly normal and natural

In everyday Egyptian speech, people might also say:

• الدواء ده بيعمل نعاس = this medicine causes drowsiness
• من الآثار الجانبية النعاس = drowsiness is one of the side effects

So the sentence is fine, but its style is a little more formal than very casual everyday speech.

In careful standard spelling, it is usually written:

الآثار

with آ at the beginning.

Many people type:

الاثار

in casual writing, especially online, but the standard spelling is:

الآثار

So if you are learning formal writing, use الآثار.

It is correct and understandable, but when talking about medicine, many speakers more commonly use:

الأعراض الجانبية

That is often the everyday medical phrase for side effects.

So you may hear both:

• الآثار الجانبية
• الأعراض الجانبية

In medical contexts, الأعراض الجانبية is often the more common everyday choice.

Yes. A few natural alternatives are:

• من الآثار الجانبية النعاس
  = drowsiness is one of the side effects

• الدواء ده بيعمل نعاس
  = this medicine causes drowsiness

• الأعراض الجانبية فيها نعاس
  = the side effects include drowsiness

They all express a similar idea, but the tone changes:

• من الآثار الجانبية النعاس = more formal
• الدواء ده بيعمل نعاس = more conversational
• ...فيها نعاس = straightforward and common-like wording